THD Bi-Valve Head

I bought this amp in October of 2008 to take the place of my 1966 Fender Bassman that was going in for a much needed filter cap job and I wanted something that was capable of the California clean sound that I have had forever with my Bassman.
If you are reading this you already know what features it has and does not have.
As far as the features I use, I would have to say evrything BUT the attenuator. I have never cared much for attenuators since I have so many great distortion pedals that I can get my tones at a whisper quiet volume at home.
Now as far as "does it have enough power?" Yes!!! Please realize I have played through a 40 watt Bassman forever to get my clean and slightly overdriven tones and when I want "The Nasty" I stomp the A/B
to kick in my Soldano Hot Rod 50."another amazing amp IF you load it with KT 88's!"
A lot of you may think 30,40 or 50 watt heads are not loud enough and all I can say is "mike your cabs and put it through the P.A. if you have a sound man with good ears!"

Now onto why it took me 6 months to post this review.
When I took possession of this head it came to me with 2 Tung Sol 12AX7's (think ECC 83 if you are from over there). Tung Sols are great tubes and I have no problems with them-- BUT-- it was what was in the power amp section that made me say " What in the heck was I thinking when I paid $1500.00 for this thing!!!"
It came loaded with Valley Art's made in China El 34's that were totally devoid of any personality. One would think that if it had 34's in it that it should have a little bit of the Plexi vibe to it but these tubes had the vibe of a belt sander.
I tweaked the amp for hours with the 34's in it and found no redeeming quality in the sound so it was time to dig into my box of tubes (new and NOS)and start experimenting.
I first tried a pair of Grooves, (Hardness 4) 6l6's and it was sooo much better that I played with them in there for weeks but they still didn't nail my Bassmans tone so I tried some Svetlana 6l6's that I had taken out of my Bassman after about three or four years of service.
Well that got me very close to my Bassman tone but not quite yet but I still lived with them for some time after I installed them.
Now these Svets were old when I put them in and one night I could tell that they were on their way out and becoming microphonic so it was back to my box of tubes.
The next set in there were a matched pair of Peavey Super Sixes that I had in the original plastic from when I bought them circa 1981
still with the price tag on them ($9.79--I wish I had bought a thousand of them at that price!).
And that is where the story ends for now because these tubes nail the Bassman tone,chime and richness that I have been used to for over 40 years.
I am not however done with the experimentation since this is a self biasing amp and I am going to order the THD YJUNI adaptors to try EL 84's and see if it gets the AC 30 sound and after that KT 66's and 77's for the old JTM 45 sound.
Thats the beauty of this head since all it takes is tube swapping to get an infinite array of tones out of it. I have not even messed with the pre-amp tubes yet because the Tung's sound so right in there.
Oh Yeah, this thing works very well with pedals too just as long as you know how to place them in them in the amp. I have some in the effects send and return and some thru the front end but I won't bore you with which is which.

So far so good as far as reliability. I am still a weekend warrior and rarely a day goes by that I don't practice or play for several hours and outside of the Svetlana's going microphonic on me no problems . The amp is super quiet until you get it past 4 o'clock and it gets a little hissy at that point but i rarely play it past 2 o'clock and that is always on the "More" setting.
I guess this rates as a 10 also

I have never had to call them but in reading other reviews everyone says they are very helpful if you have questions so I guess I will coat-tail them and give it another 10.

I have been playing since 1965 so I think I have a pretty good knowledge of what amps should sound like since I have owned (and still own) so many of the great ones.
If it were stolen I would first try to find another AA 165 circuitry Bassman like mine for a backup but still probably buy anther THD since the tube swapping factor is so much fun!
I love almost everything about it for the exception of the attenuator since I don't use it at all and the few times I did it sounded not so good to my ears.

One channel with a few knobs. Its got a cut switch, noise reduction circuit, and a built in attenuator, but all these features take away from the tone, which is why I don't use them. I do think the voltage switch is cool in that it changes the feel of the amp. A master volume and a mid knob would have made this amp complete, but the ability to swap tubes and change the output is priceless in its own right. This amp is all about cooking the power tubes, so I bring a box of different tubes with me when I gig to get that power amp distortion at the volume I need it.

HINT: you can use the attenuator to knock the volume down to bedroom volumes, but it seriously squashes the tone. Get some 6G6 tubes from eBay to knock the output down to about 1 watt (use the Low Voltage setting or you'll fry the tube). From there you can use lighter attenuation if you need to reduce the volume further. This is way better for practicing than using heavy attenuation with a more powerful tube.

My rig goes like this: Carvin CT6--> Peterson Strobo Stomp--> Bivalve--> Earcandy Buzzbomb loaded with their Green Machine speakers. This rig sounds so good that I just want to hear the amp, I don't want a bunch of pedals getting in the way.

At first, I didn't like this amp. The highs were dull and the mids weren't much better. I played around with different tubes and found that I liked various JJ tubes much better than the Electro Harmonix tubes it came with. I have another amp that came with EHs and I can honestly say that I just don't like them. That amp sounded way better with the tube swap too.

After I upgraded the tubes, I still wasn't where I wanted to be. I tried the amp through a couple Marshall cabs and I could never dial out the mud I was hearing. This amp doesn't like Marshall cabs, its just that simple. My friend turned me on to Ear Candy cabs and I ordered one. From the first time I plugged into it, I knew my cab search was over.

Now that I've got the tube and speaker thing nailed down, I can tell you what this amp really sounds like. Simply put, the cleans rival a good Fender and the overdrives rival a good Marshall, but it doesn't sound like either. It sounds like a THD. You can tube swap to your hearts content and change the character of the amp, but it will sound like a THD no matter what. For me this is a good thing in that this amp works for lots of different styles and I don't end up sounding like everybody else. Different tubes and settings yield lots of cool flavors, so its hard to decide sometimes which one to use!

The cleans are crisp and chimey, the overdrives are rich and detailed. The really great thing about this amp is that you can use the entire spectrum of your guitar's volume control and the tone cleans up without ever getting muddy. Sparkling cleans and screaming leads are just a knob twist away. You don't need channel switching or distortion pedals with this amp, just a little practice turning the volume knob quickly. I play rock, country, and jazz and it covers all of them really well.

Overall, if you're willing to spend time tweaking tubes and settings, trying different speakers, and are willing to let the amp be itself instead of trying to make it copy something else, your efforts will be well rewarded. If you're looking for something different that will fit the bill for lots of different styles, this amp may be your ticket.

I've had this amp for about a year and a half and used it on lots of gigs. Its worked just fine. So far, so good. I bring extra tubes and fuses with me when I gig, after all it is a tube amp.

I've never had to contact THD, but lots of people on the Univalve forum have posted good things about their customer support.

I've been playing about 20 years, professionally for the last 6. I've played lots of different amps in my day and I would put this amp up against anything else out there. Its got a personality all its own and its a great sound. This amp will turn heads and inspire you to keep playing, which is what a great amp should do.

The ability to swap in any combination of preamp and power amp tubes is amazing, obviously. However, I find the attenuator and noise reduction completely useless. The attenuator dulls the output sound to the point of sterility, and using the noise reduction circuit sounds akin to running your guitar through a badly buffered, non-true bypass effects pedal. This isn't exclusive to my Bi-Valve... every one I've heard has the same "problem". I'm not sure how this hasn't been picked up on and mentioned yet. Fortunately I use the amp for clean or mildly overdriven sound and the attenuator isn't needed, even in my apartment (my neighbors haven't complained yet, somehow).
I wish it had a mid control.

I use a wide variety of guitars and effects. Fender Jazzmaster, Danelectro U2, a 60's Fender Duosonic, a Fender Telecaster, a Les Paul Junior, and an Agile Cool Cat with Gibson 57 Classics. Tons of fuzz boxes: Zvex, Fulltone, MI Audio, etc. Tons of overdrives: Subdecay, Catalinbread, Lovepedal, etc. A Keely Compressor, modded Ibanez Analog Delay, Moog stuff, Electro Harmonix 16 Second Digital Delay, blah blah blah blah and a clean boost out front so my signal doesn't weep in agony from being run through so much cable and true bypass stuff. Usually, I run the head into a closed back Avatar 2x12 with G12H's. Sometimes it goes into a 4x12 with Celestion V30's, depending on the application.

This amp handles every pedal flawlessly. Fuzz pedals are no problem whatsoever. Perhaps the people complaining about the amp's inability to handle fuzz are running the treble too high, and thus getting a harsh, shrill tone when they kick in the fuzz. Its a common mistake that nearly everybody makes. Guitars and guitar amps really don't need more treble than they natively provide, and in general they need less, so cut that **** back. If you don't, I wonder how you can run fuzz on any amp without sounding even worse. I run the treble cut switch active at all times unless I'm playing funk or ska, which I don't do.

As far as my style goes, I play avant-garde jazz, electroacoustic, noise, drone, ambient, free jazz, fusion, country, blues, shoegaze, 60's pop, pre-punk, post-punk, and probably some other things that aren't coming to mind. I use this amp for everything. Currently I have it equipped with a 6L6GC and an EL34. Perfect amount of clarity, definition, note separation, punch, harmonic content, etc.. When switching playing styles or guitars I generally only need to make slight adjustments to treble, bass and attitude.

I only have 2 complaints for this category:
1) Out of the box, the head comes with 12ax7's in both positions. With this setup, the "more" input was incredibly harsh and useless to me. "Less" was not loud enough and wouldn't break up enough even with volume dimed. Fortunately, this problem is easily solved. I replaced the input tube with a 12au7 and the driver tube with a 12at7. Now, the "more" input has the perfect amount of volume and natural break-up at around 3 o'clock. Also, swapping to lower-gain tubes warmed up the sound and tamed the highs a bit, which takes us to the next issue...
2) Too much high end. But, THD had the foresight to add a handy "treble cut" switch for those of discerning taste. Ideally, one wouldn't have to cut treble so dramatically on a moderately expensive amp such as this one, but that seems to be the modern trend. I suppose that in order to compete with other manufacturers who are making far overly top heavy amps (Fender, Marshall, and nearly every boutique manufacturer), THD had to respond in kind. But hey, at least they have a "treble cut" switch.

Reading over my complaints, they seem petty since they are easily rectified, and they are both merely symptoms of the unfortunate tastes of modern guitarists. I give this head a "9" in this category because though it isn't the best amp I've heard, it is pretty damn close and half the price.

Though I have babied this thing, it does seem fairly fragile. Somehow, at some point, the 2nd power tube socket stopped functioning. I'm incredibly careful when it comes to handling the amp and swapping tubes, so I'm not sure how this happened. Perhaps I received a faulty one, or it was handled roughly in shipping.

Without exaggeration, I can say THD is the best company I've ever dealt with. Ed authorized my amp repair, did it for free and shipped it back at THD's expense... all in one week. I had thought companies with this degree of integrity were extinct, but Ed proved me wrong and restored my faith in modern commercial industry (well, as much as any single company could).

I've been playing for about 10 years. I own and have owned a lot of vintage tube amps and their modern equivalents. This is the most flexible and best sounding amp I have personally owned. If it were stolen (how would I lose it?), I would most likely buy something less expensive, as I couldn't afford another one of these at the moment. Money permitting, it would be a toss-up between this and a Marshall JTM45, though I would probably settle on the Bi-Valve.

Okay, I'll try not to repeat what the others have said. Yes, it is awesome that you can put nearly any tube in the preamp and power stages. But it's got a lot of personality on its own. If you hear a fender twin you know what you're hearing. This amp is best when you mix things up a bit. I've played with a 6V6 and EL84 (with adapter) this is where few other amps can tread.

One major caveat is that this amp works poorly with most fuzz pedals. This is fine if you play high distortion levels all the time. I like clean sounds too. And I collect fuzz boxes. So stop thinking this is the amp to end all: it ain't. 8.5 cause it does sound great.

I play alternative classic rock/punk. I like it because it has a thick rock feel. I can get a mid-overdrive that is all vox like with chiming lushness. It fits my style. I own modified strats. One of the strats has a high gain pup that boosts the imput of the amp.

Okay, with my intro you likely think I'm going to thrash it some more. Nope. With a celestion in a big or ADA stackable 1x12 cab it sounds awesome. You can run the spread from mid to high gain. I use a hot rails pup in the bridge and this thing screams. When you punch a boost pedal, wow. This amp loves to be pushed.

My fave tube combo is a low gain affair with 12AU7 and 12AT7 in the preamp and 6V6 pair in the power amp. It sounds close to a deluxe when I plug it into a second 1x12 cab with a Jenson. This thing has tons of personality but you have to coax it.

Even when you keep the amp and pedal volume consistent that amp is very touch sensitive which mean you can get a variety of sounds by changing pick attack. If you think 30 watts isn't enough, it is. This amp is LOUD.

It looks to be very tough. Massive transformers are shielded by fuses at each stage. I've dropped it and it still works. Get the gig bag. This thing needs a home.

THD is awesome. You call and they answer. No call center. Straight forward talk. Good people.

I'm a 20 year vetren of punk n blues. I would buy this again. I'm no amp builder but I think I would have liked a master volume. But this is a different kind of amp. I'd like it to take any fuzz box like a fender or crate does. Don't buy this thing for clean. I didn't and I'm not disapointed. It's pure tone, Man. It's expensive but when you put the price up against other boutique makes it's moderately priced.

c'mon you guys know already. 30 watts, swap tubes without biasing, single channel class A tube head

guitars- garbage strats with gibson pickups- classic 57' 498t. Danelctro 59 dc.
I play rock and it totally fits the bill. It has just enough gain for heavy rock( I have el34's , and JJ 12ax7's runnin), but it isn;t over the top. It doesn't hide your playing like a peavey 5150, or a mesa boogie, and thats why I like it. I love single channel amps, and thats why I got it about 5 years ago, when they came out. The only thing I feel it lacks Is the lower midrange thump of a Marshall, but I guess thats what you get with a class A amp. I love the fact that I can clean it up by rollin off the volume. The distortion isn't brutal, but musical ,and the feedback is musical, as if the amp knows what key youre playin in. It is loud , but not as loud as I need all the time. Sometimes I play halls and the midrange just gets eaten up by the room, and the drums. In a club setting it's great, and it records like a dream.

I gigged this amp for 5 years in a rock punk band. I have never had a blown fuse during a show. it has been rode hard and never failed me at a gig.

Awesome! My amp died during a rehearsal, and I brought it to a local repair shop. He sussed out the problem, called THD, and in a few days he had the parts and fixed free of charge. THD hooked him up with a bunch of yellowjackets as payment. I had my amp back in less than a week, and I live in New Jersey,THD is in Cali.

Had it for 5 or 6 years. I also have a peavey classic 30. I will never sell it because itis so unique and would like to keep it in my tone arsenal. I just wish it was real loud, and had more midrange crunch, so I guess I better get a marshall. It could use a midrange control knob.

Single channel hi/lo input. Effects loop. Built-in Hot Plate Attenuator. Noise Reduction. A little more than I usually like in an amp (The more stripped down, the better!) but EXTREMELY easy to dial in. Instructional pamphlet also very helpful! TWO features absolutely blow my mind. FIRST, you can run up to a 2 OHM load! Awesome. But secondly, and MOST importantly, the amp is automatically biased, which means you can plug almost any tube you like into it, in any combination! This amp has a maximum output power of 30 Watts Class A, and can out-perform almost any 50 watt Class AB amp in my opinion. I usually use it paired up with a Marshall 1960A Lead 4x12 cabinet, in conjunction with a SOVTEK Mig 50 paired with a Marshall 1960B Lead cabinet. The SOVTEK takes care of the lows and mids, but the THD adds to the lows, and cuts through with the highs. Well done!

I play a Gibson Les Paul special, loaded with an active EMG 81 & 85. This guitar paired up with aforementioned configuration produces what I call the 'bikini effect'. A great hi-lo blend. Very 80's metal. However, I also use a 1972 reissue Fender Telecaster Deluxe, which uses 'wide-range' pickups, which give me all the mids, lo's or hi's I need, depending on the pickup selector. This amp is exactly what I needed for my sound. Very little noise, depending on which tubes you are using. The lo input gives you creamy, smooth bluesy tone. The hi input gives you an edgier, more aggressive tone, and breaks up around 5 or 6. I love the natural overdriven sound of this amp, and use no overdrive or distortion pedals to achieve a very heavy, crunchy overdrive. If you want to hide all your mistakes with this amp, don't count on it. This overdrive is very 'true' and will let you know when you screw up, but will tear the faces off your audience when you nail that solo. Just to lgive you an idea of what kind of music I play, I'll give you a hint: I'm tuned B standard, dropped to A. If you love heavy strings, but can't achieve a bright tone, this is your amp.

This baby comes equipped with a full steel chassis. It's a little heavy, but there's a good chance it would survive a fire or a 20 foot drop. Heavy duty. As far as electronics, I have not had a single problem yet. Because the amp is auto-biased and can handle a variety of different tubes, there is also a hi/lo voltage setting. So if you're going through a lot of tubes, you're probably the one to blame. I've had a pair of Valve Art EL-34 power tubes, and a TUNG-SOL A12X7 input and drive tube in since day one, which was 6 months ago. They both sizzle like the day I put em in, and remember, I like it loud and heavy!

Haven't had a reason to contact customer support.

I've been playing since I was 12 (10 Years) and I've played Marshall 2061X, Orange AD 30, Dr. Z-28, Hi-Watt Custom 20 etc. and the only other amp that compares in tone is a Bad Cat 30 watt class A. But if you'd like to pay about $1000 less for the same quality, go THD. The only thing I may be frustrated by is the fact that this is the Pandora's Box of amps. I may go 30 years before finding the right configuration of tubes, but it's the last Class A amp I'll ever buy!

Single channel hi/lo input. Effects loop. Built-in Hot Plate Attenuator. Noise Reduction. A little more than I usually like in an amp (The more stripped down, the better!) but EXTREMELY easy to dial in. Instructional pamphlet also very helpful! TWO features absolutely blow my mind. FIRST, you can run up to a 2 OHM load! Awesome. But secondly, and MOST importantly, the amp is automatically biased, which means you can plug almost any tube you like into it, in any combination! This amp has a maximum output power of 30 Watts Class A, and can out-perform almost any 50 watt Class AB amp in my opinion. I usually use it paired up with a Marshall 1960A Lead 4x12 cabinet, in conjunction with a SOVTEK Mig 50 paired with a Marshall 1960B Lead cabinet. The SOVTEK takes care of the lows and mids, but the THD adds to the lows, and cuts through with the highs. Well done!

I play a Gibson Les Paul special, loaded with an active EMG 81 & 85. This guitar paired up with aforementioned configuration produces what I call the 'bikini effect'. A great hi-lo blend. Very 80's metal. However, I also use a 1972 reissue Fender Telecaster Deluxe, which uses 'wide-range' pickups, which give me all the mids, lo's or hi's I need, depending on the pickup selector. This amp is exactly what I needed for my sound. Very little noise, depending on which tubes you are using. The lo input gives you creamy, smooth bluesy tone. The hi input gives you an edgier, more aggressive tone, and breaks up around 5 or 6. I love the natural overdriven sound of this amp, and use no overdrive or distortion pedals to achieve a very heavy, crunchy overdrive. If you want to hide all your mistakes with this amp, don't count on it. This overdrive is very 'true' and will let you know when you screw up, but will tear the faces off your audience when you nail that solo. Just to lgive you an idea of what kind of music I play, I'll give you a hint: I'm tuned B standard, dropped to A. If you love heavy strings, but can't achieve a bright tone, this is your amp.

This baby comes equipped with a full steel chassis. It's a little heavy, but there's a good chance it would survive a fire or a 20 foot drop. Heavy duty. As far as electronics, I have not had a single problem yet. Because the amp is auto-biased and can handle a variety of different tubes, there is also a hi/lo voltage setting. So if you're going through a lot of tubes, you're probably the one to blame. I've had a pair of Valve Art EL-34 power tubes, and a TUNG-SOL A12X7 input and drive tube in since day one, which was 6 months ago. They both sizzle like the day I put em in, and remember, I like it loud and heavy!

Haven't had a reason to contact customer support.

I've been playing since I was 12 (10 Years) and I've played Marshall 2061X, Orange AD 30, Dr. Z-28, Hi-Watt Custom 20 etc. and the only other amp that compares in tone is a Bad Cat 30 watt class A. But if you'd like to pay about $1000 less for the same quality, go THD. The only thing I may be frustrated by is the fact that this is the Pandora's Box of amps. I may go 30 years before finding the right configuration of tubes, but it's the last Class A amp I'll ever buy!

Single Channel, 2 preamp tubes, 2 power tubes in any combination. Volume, Treble, Bass controls, hi-cut switch, low and high gain inputs (using one or both sides of the first preamp tube)Multi-tap output transformer, effects loop, line out, Hi-low power switch, and built-in speaker attenuator. Actually alot of features!

This amp is very sensitive to different guitars, pickups, and speakers, to say nothing of tube types. You can vary the sound any way you like and it will always be musical due to its class A configuration. I've found my best signal path to be Barden pickups in a strat with a Warmoth Boat neck and Callaham bridge block and saddles, using a KT-88 and KT-77 power tubes, with 5751 and 12at7 preamp tubes with the high gain input. The amp goes into a 1x15 mojo cabinet with a EVM-15L. This amp goes from clean to driven with the turn of your volume knob, with the ability to get all shades in between. Getting musical even-harmonic feedback at will with the guitar volume knob on 4 and the sound relatively clean is unattainable with any other amp i've tried.

Built very solid, parts are outsourced to the same firms that make parts for Boeing I hear. I carry extra tubes but that's all. So far so good

extremely friendly, helpful, and best of all, AVAILABLE!

I've played 22 years, used all kinds of old and new amps. This amp is in a class truly by itself. The purity of sounds has almost eliminated my need for any pedals. The only drive pedal that doesn't take anything away from the amp's tone is the Klon Centaur, so I still occasionally use that.

Single Channel, 2 preamp tubes, 2 power tubes in any combination. Volume, Treble, Bass controls, hi-cut switch, low and high gain inputs (using one or both sides of the first preamp tube)Multi-tap output transformer, effects loop, line out, Hi-low power switch, and built-in speaker attenuator. Actually alot of features!

This amp is very sensitive to different guitars, pickups, and speakers, to say nothing of tube types. You can vary the sound any way you like and it will always be musical due to its class A configuration. I've found my best signal path to be Barden pickups in a strat with a Warmoth Boat neck and Callaham bridge block and saddles, using a KT-88 and KT-77 power tubes, with 5751 and 12at7 preamp tubes with the high gain input. The amp goes into a 1x15 mojo cabinet with a EVM-15L. This amp goes from clean to driven with the turn of your volume knob, with the ability to get all shades in between. Getting musical even-harmonic feedback at will with the guitar volume knob on 4 and the sound relatively clean is unattainable with any other amp i've tried.

Built very solid, parts are outsourced to the same firms that make parts for Boeing I hear. I carry extra tubes but that's all. So far so good

extremely friendly, helpful, and best of all, AVAILABLE!

I've played 22 years, used all kinds of old and new amps. This amp is in a class truly by itself. The purity of sounds has almost eliminated my need for any pedals. The only drive pedal that doesn't take anything away from the amp's tone is the Klon Centaur, so I still occasionally use that.

The SN is 220, I bought it new from Corner Music in Nashville, TN but it looked like it had been there for some time. I play heavy praise and worship music and also am a closet 80's shred fan,kind of shows my age. Because of the music I play I have to have an amp that goes from pristine clean to grinding metal. I have been on an amp quest for some time, I was really wanting to buy a multi-channel amp, which this one is not. But when I tried it out in the store I was hooked on the tone and versitility of tube swapping. When I got it home where I could really strech it out I was amazed by how loud it was, Class A amps are deceaving with their power ratings. I have a Marshall 4X12 cabinet loaded with Celestion V30's. I loaded the head with 2- 12AX7C9 Chinese preamp tubes and JJ KT88 power tubes and MAN! what a tone. This was a harmonic rich, air pushing low, beautiful singing tone that was breathtaking. Be advised though that this was power amp distortion and not buzzy preamp distortion and every little nuance of your playing will be heard. As you roll off the guitar volume knob the beast settles into a purring kitten. I wish I was quick enough with the volume knob to use this as channel switching because the tone is so sweet I hate using any other head! Well I'm sure going to practice try and find a way, I've even been thinking about buying another head and setting up for just a clean sound even though I can't afford to. Sounds like every other tone junkie I'm sure!

Man, this is where this head shines. I've tried so many different heads and there was always something about the tone I didn't like. It seens like no matter what tube combination you use, the sound is cool, but there are some that I like more than others. Of course as stated above the KT88's were my favorite sound followed closely by Tung-Sol 5881's. That's the beauty of this amp with just a few simple tube swaps you can dial in your own custom tone. I have several different guitars I play through the amp : Gibson Les Paul Classic w/burstbucker pro pickups, Jackson Dinky w/ Seymore Duncan 59, Ibanez RG550 and RG560 both with Seymore Duncan 59's. Even thouht the last 3 guitars have the same pickups and Floyd Rose Tremelos they still all sound a little different because of the different type of wood used in the body and neck of the guitars. Be advised that some people are not going to like class A amps, They are very much in your face. If you like the sound of a buzzy Mesa type preamp distortion you may not like the sound of this amp. If you like power amp distortion dripping with harmonic overtones this is the amp for you.

It's new and I haven't had the chance to gig it yet, however, by looking at the quality of construction I would be confident to only bring some extra tubes. The head will even continue to play if one power amp tube blows and it has lights on the back that shows you which tube is bad.

Here is another reason I am so excited about this amp, The amp had been sitting in the store for so long the original shipping box, owners manual, and warrenty card, had been lost. I got their number off the website and called to register the amp. I contacted Ed De Genaro of THD and told him I had just bought a THD amp and before I could tell him why I called, He thanked me for buying one of their products! How many times has that happened when dealing with customer service anywhere? He answered all my questions and treated me like a rock star, I wish all companies were like this!

For the price I payed this amp is an increadible value. Like I stated above I was looking for a multi-channel tube head and played several in the store that sounded good but I kept coming back the one head that sounded GREAT! No channel switching, no MIDI, no reverb (except for the natural reverb it makes with voume!)But tons of pure addictive tone!

Save your money, sell your car, get a loan. Do anything you can to get one of these amps. They are special.

I am blown away with the sound of this amp. I have a couple of vintage Fender tube amps that sound good but doubt if I play them much anymore.

Just bought it. We will see.

Just bought it. We will see.

Buy one.

The previous reviews set forth accurately the cool features of this amp. I received my first Bi-Valve three weeks ago and liked it so much I had Musicians Friend ship me a second one. A second channel would be nice, but one can't have everything in a Class "A" amp. I like blues and hard rock which this amp can more than deliver.This amp is very quiet with good cables. Because of the mix and match possibilities she gets a 10.

The Bi-Valve is a tone monster and can be used for almost any style of music. Could probably be used for metal with the right trash in front of the pre-amp. I decided to get the second amp to use as a channel two. I'm using a Keeley/Framptone amp switcher which works like a dream. The Framptone is quiet and does not color the sound. My first amp is loaded with Groove tube GE 6L6's while the second has Groove Tube EL34M's. Im getting the best that each tube has to offer. Im running these amps through a Mesa Road King 2x12. I get an airy and open tone (6L6s) with the "open back" side, and a tight and responsive tone(EL34's) on the "closed back" side. The attenuator allows for some great power tube distortion. The choice of inputs (more/less), power level( hi/low),attitude control,tubes (preamp/power),and attenuator settings open up a new world of tinkering for tone. My Gibsons sound great as do my Fenders. The amp is quit powerful and has no trouble pushing a four ohm Road King 4x12 cabinet. With the full power settings the B/V can get quite loud.

Just got-em so I have no real basis to evaluate. Seem to be built like the proverbial brick !!!!house. I would run-em without a back-up.

My first amp came on a Friday and was missing the power cord. I immediately called THD and advised of the situation and they mailed me a cable the following Monday. They only asked me for the amp's serial #. I Received the cord on Wednesday. The warranty is two year, transferable. I have E-Mailed questions on three occasions and received responses from Ed DeGenaro w/i two or three hours.

Been playing on and off for fifteen years. I own some Boogie gear
(Road King, Stiletto, Lone Star Special) and a Marshall JCM 900.Have various Gibson and Fender guitars. The Bi-Valve has its special place in the collection and cannot be duplicated by my other amps except, possibly, in some areas, the L.S.Special. This amp is too cool. On its face the price may seem high but you wont mind once you try it. If I got ripped off I would damn sure replace the Bi-Valve.

Rock-On!!

THD BiValve 30 Watt Head Single channel amp, hi and lo inputs with a significant difference in volume between them, bass, mid and high frequency eq controls and attitude control to adjust the tightness of the sound being fed to your speaker cab.

The amp also has a high and low voltage plate switch that works great to allow for different tones from the same tube combinations and a built-in hot plate attenuator, which, for me, is a fantastic feature, since it allows me to use the amp for low volume/high tone practice at home. FInally, there is a light bulb feature for noise reduction, which also works really well.

But the one thing that sets this amp way apart from the rest is the fact that it's 100% self biased and allows you to use any power/preamp tube combination under the sun! All these features provide you with a real tone lab and, most importantly, a W I D E road to finally find your tone! Two big thumbs up on features!!!

All in all this amp is built like a tank and constructed very well. I bought mine used on ebay and had it shipped from the US to Italy, where it got "lost" in customs for a couple of weeks - no problems whatsoever - the amp sounded great from the day I got it and it just gets better and better everytime I play it.

In just two words - SIMPLY AMAZING!!! There is apparently no limitation to the variations of sounds you can get out of this amp, except for metal, which requires you to plug into a boost or distortion pedal in front of it. Aside from this, this amp can deliver just about any sound you want.

This amp is extremely touch sensitive. Any change in attack is noticed immediately. It is also very transparent and, no matter how hard you drive the tubes, your guitar's and playing style come through it clearly.

SInce it's a single channel amp, one of the things I had to get used to was to control the tones from my guitar's volume knob, but after about a week of playing, I cannot imagine going back to channel switching.

The amp is extremely quiet, even at full volume on high input, thanks to the light bulb. Without it there is a little hum, as well as when using single coil pick-ups, even if they're hum-cancelling.

I play mostly blues and classic rock, but go to hard rock and some modern metal once in a while. For the latter tones, I'm currently using a Fulltone Fat Boost in combination with the boost feature on the Radial Loopbone and it works really well for me. The tubes are JJKT77 and JJ EL84 in the power section and JJ ECC803S and JJ ECC83S in the preamp section. I use the low voltage switch and it works just fine for me.

Built like a tank. No problems whatsoever!

Ed De Genaro is the greatest guy when it comes to your questions. I've e-mailed him several times to ask questions before I bought the amp (when I was reviewing it here) and after to ask questions about the amp itself and other products to go with it. He always answers the e-mails, usually from one day to the next and he's a great guy to talk to.

Together with Tom Anderson (Roy and Co.), other companies should take note of how customer service should be done!

Fantastic value! It isn't cheap by any means, but it's worth every penny and all the wait to get it. If it was stolen, I'd get another one.

One word of caution and, actually, confirmation of a few of the reviews I've read here: be prepared to spend some bucks on tubes, as you will go nuts experimenting with them. I'm still buying tubes and I'm sure I will be for a while still...but it's a great and rewarding experience, since everytime you get a new type/brand and put it in, it's like getting a new amp or for sure a new variation.

Have fun!

I'm sure you've read in the other reviews the greatest feature this amp hold. The ability to put in almost any tube combination you want without having to rebias the amp. Just plug and play.

On top of this the amp has a very cool and modern look about it.

It's a 30 watt one channel monster. Many people might be put off by the fact that it doesn't have the ability to switch between two channels. I would suggest getting a pedal or if you are crazy like me, get another head and ABY them. Currently I am running the THD through a Hartke 410 cab with a VHT 212 cab. I have a Fender Prosonic head that I am running through an old Hartke 412 cab with celestions. With the ABY I have the ability to switch between the amps or play both of them at the same time. This on top of the tube switching capabilities allows me to have a multitude of sonic abilities. Let me tell you, when I run both together, oh my god, pure molten lava comes out.

Another cool thing about this amp is the hot plate power attenuator. This allows you to squash the signal and get the right amount of saturation on your distortion at whatever volume you play at. Many people say it affects the sound in a bad way, but I don't think so. To me it sounds great.

Even though this thing has only one channel, you can switch the tubes, cabs, and guitars to get ANY sound you want if you only take the time to experiment. This baby is a sound scientist's dream amp. Currently I have tried only one tube combination: 2 Groove Tube 6l6 and 2 Groove Tube 12ax7 tubes. It sounds fantastic. The distortion sounds great and is not too saturated allowing all of the notes to ring through. This amp will surely show you the flaws in your playing as you cannot hide behind saturation.

This baby will get plenty loud. Without using the hot plate I cannot get it over about 3 when I am practicing with the band, so I find it difficult to get a lot of distortion without using the hot plate, although I'm sure if I did some tube experimentation I could.

The guitars I use include the following:

1970s Gibson double customized Les Paul Custom with three pickups
1990s Gibson Nighthawk Special with three pickups
1970s Gibson Marauder
1994 Epiphone Les Paul standard (soon to be customized)
Early 90s Wayne's World Ltd. Edition Squier Stratocaster
2004 Dean Exotica Accoustic

All of these guitars sound great through this amp.

This thing is like a tank and very heavy. I have yet to gig out with it so I can't say how reliable it will be when I start. So far I have had no problems.

This is where THD really shines. If I could give them a 20 in this department I would. I emailed Ed Deganero multiple times about the amp a I received a response every time within a couple of hours. I needed some cleaning tips and the manual(which he promptly emailed). One time he even called me at my contact number no more than 5 minutes after I sent an email so he could talk to me directly. I asked him some questions on speaker impedance and how it relates to the amp. Technically I wouldn't think it is his responsibility to explain this to me, but he did so in such an efficient and personable manner that I nearly couldn't believe it was actually happening. I have NEVER received customer support of this level ANYWHERE! These guys are great and will do anything in their ability to make sure you are fully satisfied with their amp...and trust me, you will be.

I have been playing seriously now for about a year or two and I can't say enough about this amp. If it was ever stolen I would certainly buy another one without any amount of hesitation. To anyone who is looking to get a $2500 head, do yourself a favor and pick up one of these instead. You will be glad you did.

The only thing about this amp is the fact that it's hard to find in a music store unless you live in California. I took the word of these reviews and bought this amp without ever having listened to it in person. There are some sound samples on www.thdelectronics.com that are good, but depending on your speakers it is nothing like hearing this baby in person. I am so happy I took the chance, it was well worth it.

2004 - Versitile Yes with able to change tubes without re-bias, single channel class A, the amp is extremely loud for 30watts. Excellent for rock. Takes to good foot pedals with the best. Features are covered in other reviews.

Guitars - PRS McCarty; Swamp and fender american strat. The amp has the cut-through in a multi-guitar band that you need. It does require a cabinet loaded with good speakers. (vin30 and g12h30) If not it will sound thin and harsh. I use a boss noise supp., so noise is never a problem. The amp does not have a great deal of gain, even at full throtle. I use a H & G Tube Factor for more gain. However it will kick your ear-in-the-butt at max vol. Think of a Marshall Plexi with class A attack. Your chops better be up to power.

I've owned the amp for 2 years with no problem. No backup. However I own or have owned over 30 amps in my 20+ years of playing this one rates with the best.(TopHat,VoxHW,Hughes ect...)
uilt like an anvil.

Andy was great to deal with. I highly recommend if this is your kind of Tone...

20+ years of R & R, I don't think you could go wrong with the THD-Bivalve. Solid in all areas.

Got to start by saying univalve.net is a fantastic site for THD users, don't talk to THD before you visit this dedicated web site for THD heads. A great bunch of players and answers to every imaginable question THD and more...

Features, everything I need.... took some getting used to the unique THD features such as Hotplate, Attitude & unique EQ response. But very versatile and sounds that are everythign they've been described as.

I am posting this review after 16 months of ownership... so I think I am across what it can do now... : )

Using '92 Les Paul & Custom Tele with SD STK1 & Lil'59,
Good for country & western music.. lol.. Rock, roll, not a high gain monster... pure pedigree with attitude...

It's a brick... all quality here people, streets ahead of the pack on this aspect.

THD are second to none in service... irrespective of what a stray comment on this site may say. Go to univalve.net to get an idea of what I am talking about.

Yes I have had an email that they did not answer on day 1, but they are busy, busy. I rang 'em and persisted and they went out of their way to help me.

I ordered a 240v conversion kit - unreal support.... direct from Ed DeGenaro (serious pro by all measures - helping lil' ol' me get sorted - what a guy!). Too easy!

Killer...

I am not sure of the year, this is a single channel tube amp. I love it. It has everything and more than I need in an amp to play in a band situation. It isn't a fancy amp other than how versatile 1 channel is. The tweakability is where it is at.

Thinking that most amps with 2 channels lose something on the way, I am giving this amp a 10.

I am playing a Peavey Generation Series 1 guitar with a duncan distortion in the bridge and a classic strat pickup in the rear. I run this through a wah, and I run a DOD bifet preamp in the loop for solo boosts. The amp is quiet so far, I swapped one of the 12 ax7 out for an at 7. It sounds less preampy. I am runnin this through a Z best cabinet which more than beats the competition.

The amp gets a nice distortion that can be cleaned up nicely with the tweak of a volume knob (on your guitar). This is of course if you are like me and prefer a less preamp gainy tone.

Otherwise you can use whatever tubes float your boat. I am fairly new to this and haven't experimented too much, but my bet is that BRUTAL DISTORTION is available depending on your tube selections. Like 2 12 AX7 and some KT 88's!!. I think this amp can get most tones pretty close. EVEN brutal!! It has USABLE distortion not muddy. Keep in mind your speaker cab plays into this as well.

I have no opinion YET!!

I emailed Ed Degenero and he was nice and helpful.

I have been playing 25 years. If it were stolen or lost I would get another one. I love that this amp is completely your own beast. You can do with it whatever you want tube wise. This gives it major appeal. But not to be forgotten, this amp sounds great. It is hard to make it sound bad actually. The tonal controls are very usable and very sensitive. I have stopped looking for tone after finding this amp. This amp gives me so much satisfaction I cannot explain in this box!! Anyone spending $3000 on a boutique amp should be looking at buying 2 of these!! The distortion is so usable and musical sounding. Even at brutal distortion levels (which isn't my thing) this amp sounds very clear sounding with the right tubes.

As listed already, but basically:
30-Watt Class-A, Single Channel Amplifier head
Built in THD Hot Plate
Effects Loop, Line Out w/Level Control
Hi-V/Lo-V Voltage selection
2 Inputs More and Less (only 1 can be used at a time and you can't A/B them)
Best Feature: Change Pre- and Power-Amp tubes endlessly to hone in your sound.

This amp pretty much suits my needs perfectly. Most off the shelf amps have some good tones, but none of them really are "me." While,
I'm still experimenting with different tube combinations I'm getting much closer to the sound I want.

The only feature I wish this amp had would be the ability to A/B the Hi and Lo inputs, making it a quasi-channel switching amp.

Sound is very subjective, but this amp is getting me closer to the tone I am seeking. The ability to change the tubes to almost any type made is one of the best features and the primary reason I purchased this amp.

I play just about every style of music from Classical to Jazz and Country to Rock. This amp is very touch sensitive and dynamic. If you play sloppy through this amp, you'll get a sloppy sound, but play with some feel and good technique, and this amp will sing. If I have one beef with the amp, it would be when the Hotplate attenuation is active. If you crank the amp and play with some force, there is a noticeable, albeit brief, "sag" and dropoff in the sound. I've only experienced this with the HotPlate active, but I guess it wouldn't be an attenuator if it didn't attenuate the volume.

Playing through the More input will give you an edgy clean to a nice, smooth distortion. I'm not sure if you'll get metal sounds from this amp, but hard rock sounds are abundant. Again, depending on the tubes you use, you can get more or less distortion. The Less input is clean throughout the whole volume range, with maybe a slight edge at peak volume.

I use the THD 2x12 cabinet with this head and get some great low end with this amp. My guitars are a Van Halen Music Man, Fender Lite Ash Strat, PRS Rosewood McCarty, and a custom Tele with Seymour Duncan Phat Cats. All of these guitars sound great through the amp and each add their own character to the amp. One thing to note...my volume knobs on the guitars actually work! With a channel to switch to for leads, I've found this amp to be very dynamic in responding to volume settings on the guitar.

I'll give it a 10 because it's been rock solid, although I've only had it about 1.5 months.

I sent an email to THD regarding tube specs and performance with the amp, but never got a response. Not a huge issue, I was just looking for some extra resources on tubes.

I've been playing for 17 years and gone through my fair share of gear. This amp is one of my all-time favorites. I really feel like this amp allows my personality and style to show through. So far, I've only used EL-34's in the power section (I swapped the stock ones, which weren't as "alive" as the Groove Tubes), but will eventually try some other styles of tubes. Also, I put a 12AU7 in the Driver position and it really cleaned the preamp section up (I favor Power amp overdrive more than Preamp distortion).

I looked at the Mesa Boogie Lone Star and Dual Rectifier, some Traynor amps, B-52, Vox, and Dr Z before choosing this amp. I think the allure of tube swapping really grabbed my attention as the other amps did not allow customization of the tones as much.

Really simple...No boost, no reverb... More and less inputs, high-cut switch, 2 speaker outs with selectable impedance switch, effects loops w/ effect out level control, bass, treble (no mid), volume, attitude (shapes the distortion character), high/low voltage switch, built in hot-plate attenuator, noise-cancelling circuit w/ a really cool red bulb reminiscent of old Fender amps...and the best part...complete tube swapping freedom without ever having to bias! I give it an 8 for versatility just because no mid, no channel select, no boost, no reverb, etc.

I've owned this amp for about 4 months and I've played Strats, teles, 'Pauls, an Ibanez semi-hollow, even my acoustic guitar. This amp sounds sweet no matter where it's set at and is perfect for just about everything you could think of. It doesn't do the Mesa thing though...But it does give you amazing tones. Lots of harmonics...My favorite settings so far are an EL34 and a Mesa 6L6 together and a 6550 and an EL34 together. The 6550 gives it a slightly darker sound that compliments my Tele AWESOME! I run the volume all the way up, the attitude about 2 o'clock, bass at 2 o'clock and treble at around 10 o'clock. It gives a sweet, complex, dark and rich sound.

Built like a tank, I've gigged with it quite a bit and it never gave me any trouble. I've heard you can even use this thing to test good and bad power tubes (I wouldn't recommend it...but it's possible)

Dave at Avatar is an amazing guy to do business with. He sells awesome products and backs up everything he puts out the door. I know he along with Ed and Andy at THD would rapidly take care of any situations should they arise. Ed promptly answered every question I had about this amp.

I've been playing guitar for about ten years now and I'm by no means a master, but I know good quality and good sound when I find it, and this is it. If you are a cheese-head who's idea of good tone is the volume and gain pushed past 11, this ain't your amp. But if you are looking for an amp that will let you find your sound, this is it. I played Vox AC30s, high end Marshalls, high end Fenders, Mesas, etc., and could not find the "sound" I had in my head, until I took a chance on the BiValve. I would replace it with 2 more if it were ever lost or stolen!

Serial #0665...not sure what year that equates to, but purchased new from Dave at Avatar Speakers in July 05. Check out http://avatarspeakers.com/ for some great prices on THD & Avatar Speaker combinations. Regarding features, this amp could not be simpler...single ended, class A, treble, bass, no boost, no reverb, not even a midrange eq. The beauty however is the engineering on the inside with the ability to mismatch power tubes...even run on a single power tube. The built in THD Hotplate is a plus when set at 12:00 or higher but tends to over-compress & choke the tone when set at quieter volumes. The full-power switch bypasses the Hotplate entirely for the best no-compromises tone. A Hi/Lo voltage switch lowers the voltage from 450-470 plate voltage to 300-320. Lower voltage produces warmer and more spongy character...and, maybe even more importantly, to use the great old 6v6, 6k6, etc tubes from yesteryear that can't tolerate high voltage of most amps. The "light bulb" feature reduces hum somewhat but I find that I rarely use it...at least not at reasonable volumes because it seems to take a little of the shimmer off the tone...but this could just be in my head. The "attitude" control operates like a subtle drive control, making the overall tone more aggressive. Two inputs "more" and "less", as the name implies offers the choise of a hotter vs lower gain input. I find myself using the "more" input exclusively and using the attitude control to put some "hair" on the tone. A dummy load allows you to unhook the speakers for direct recording, but you'll need a cab simulator or you'lll get some pretty funky tone. All things being equal, this design is a thing of beauty!

I'm primarily a single coil guy...my primary guitar is a Warmoth VW set up like a strat w/ a killer Rio Grande Muy Macho set (Stelly, Muy Grande, Muy Grande)and flame maple top & maple neck. The combination of the beefy Rios and the bright flame maple top & neck make for a very balanced tone and sounds incredibly "3D" thru this amp. Right now, I'm experimenting with a Boss VF-1 multi-effects in the EFX loop with great results, but even without the VF-1, and plugged straight into the "more" channel, the #2 & #4 positions it give off an almost "chorus-like" high-end chime...very satisfying.

I've not gigged with this amp yet, but I'm pretty OC about stuff breaking...I'd bring fuses, tubes and a Digitech modeling pedal to plug into the PA if all else fails. That said,it appears that Andy Marshall and his crew are also OC about building a bulletproof amp...I have no doubt that this amp will survive whatever I can dish out.

Ed DeGenaro at THD is a guitar player's guitar player and the nicest guy you'll ever email. THD's has a reputation as a company that spends the $ to make the very best over-engineered product out there and then stand by it religiously. It was the tie-breaker in my decision to buy this amp sight unseen, based soley on the MP3s and the Harmony Central reviews. They exemplify the saying, "...if you don't take care of the customer, somebody else will".

I've been playing 35 years blues/rock, roots, and stright up rock...and is influenced by guys like Jimmy Thackery, Bugs Henderson, Johnny Winter, David Grissom, Gary Moore, etc, and this, IMHO, is the perfect amp. I've no doubt that, with the right distortion pedal and a closed back cabinet, you could go for any modern tone. The bottom line is that I can not say enough about this amp, other than this is the most satisfying purchase I've made in 35 years...it's simply the best amp I've ever owned. I'll still pick up a stomp box here or there, but my search for basic tone is over.

Read features below. The only 2 I cared about when buying it were

1) Class A
2) Self Biasing

The built in Hotplate is Ok, but I seriously doubt it will get used much. I thik the THD Hotplates are inferior to other attenuators, including the Dr. Z Air Brake. But that does not detract from the amp being exactly what I was after.

I always thought the Bogner XTC in the blue channel with the Class A option engaged was the best tone I had ever heard. Tight and punchy, with tons of sweet crunch tone that was like ear candy. Well, this amp with a tube change sounds as close as you can come at less than 1/3 the price. I like Plexis, but I also love the harmonics of a Class A amp. The BV gives you both, but be prepared to work a bit with the amp. In the LV (low Voltage) mode the amp is thicker sounding, but not as quick off the fretboard. The brown sound is found here, and the volume is lower. I like the higher voltage sound, as it is punchy and quick and much more suited for the classic rock I play. Big crunchy chords and stinging Zep type leads. Great stuff.

You will end up swapping tubes until you go mad, unless you first take a step back and see that the EL34s it comes with sound excellent themselves. A tweak here and there, and they will do any Marshall sound in the book except metal. Power tube distortion is what it is all about. The BV sounds great.

Not much to go wrong, but stuff does happen. THD is as good as any amp builder.

They always answer Emails ...

Just what I was looking for. I will go down the tube swapping route, just to see what is out there, but I got excellent tone right out of the box. I love a huge plexi crunch sound, and this amp delivers that with lots of Class A overtones thrown in. Leads are easier in the Low Voltage (Van Halenesque) setting, and 80s metal players will like playing in that territory. The built in Hot Plate is cool, but I will never use it. This is a great amp for the money.

Features have been rehashed ad-naseum in the many reviews below; all tube class A single channel head. Classic, straightforward design with a few twists. Used at home for practice and some recording. Plenty loud!

I use this amp mainly with my Strats. Cab is an Avatar 2x12 with Eminence Private Jacks (Greenback clones). I play bluesy rock, heavily influenced by Deep Purple, Jimi, Robin Trower, etc. Perfect for what I like to play. Just for fun I plugged my Jackson with EMG's in last night - it was just plain creamy! This amp will take a wide variety of tubes, so it is a tone tweakers dream come true. I am currently using a 12ax7 in the pre, a 12at7 in the driver, and an EL34 with 6L6 combo in the power section. This tube combo delivers what I'm looking for; the guitar just sings, and this is with the volume at 1:00 using the attenuator. Harmonic overtones galore, natural tube compression. Roll your Strat back to 7 on the volume, and you will nail Blackmore's tone on Machine Head. I've never played through an amp that was so sensitive to the guitar's volume knob. That's one of my favorite things about it. Works well with my pedal collection. I don't use the effects loop (call me old school). Clean input (called "Less") I don't use too much. Nicely balanced tone, no icepick highs, punchy, articulate, touch sensitive. Best amp I've every played through, and I've been playing since 1975. I bought this amp without having played through one first based on the reviews here at HC, as well as the cult-like following on the THD online forum. I was not dissapointed in the least. Fantastic sounding amplifier.

I've only had it for a couple of weeks, so can't comment too heavily on reliability. However, it is built like a tank. Loads of steel, weighs a ton. I don't anticipate any problems.

I've emailed THD a couple of times with questions, they answered me promptly. I only live about 40 minutes away from their shop, so they gave me an open invitation to bring the amp down anytime for any reason. How cool is that?

I bought this amp on Ebay and got a smokin'deal, as it was brand new in the box. It was part of a music stores overstock sale, and they goofed and put it in the wrong category, so nobody was bidding on it. I was expecting to drop over a grand for one. I've been playing since 1975. I mainly play Strats, however I do have a couple of humbucker equipped guitars when I get into that mood. Pedalboard with the classics, wah, fuzz, OD, Univibe, etc. Love the tones of Blackmore, Hendrix, Trower, Schenker. With this amp and my pedals I can do all of those and more. If it were stolen or lost I would replace it with the same amp. I was considering a Dr. Z, but the ability to swap out tubes in the THD was too good to be true. I can't imagine anyone owning one of these and not being able to nail their dream tone after some experimentation. The only thing I wish you could do is A/B between the two inputs. I've owned many amps (Fender, Marshall, Peavey, Roland) and none have come close to this one. Even tried one of those modeling jobs for a couple of years.... nope! There is nothing like being able to control the gain with just the guitar's volume knob. It's like having 5 different overdrive pedals under your little finger. Kick on the fuzz, and it will nail Jimi's tone on Spanish Castle Magic. I could go on and on. Just buy one, dammit!

What can you say about features? It is a one channel amp, kind of old school and has to be driven from the guitar. These are definitely not bad things we just arent used to doing things this way anymore with all these new multi-channel amps.

I play a Gibson Les Paul Elegant. I use this amp for kind of a southern/classic rock/ blues sound but just a little more modern sounding. this amp is as quiet as a mouse, I had a fender hot rod deluxe and it was pretty quiet but I have never played through and amp that was this quiet. I had trouble dialing in the right tone when I first got this amp but after playing with a lot of different tube combinations and learning that if you sit right in front of the speaker cab with the volume cranked any amp will sound harsh I think I found my tone. this amp can go from country brite and clean (with the right tubes- 6L6's or a 6L6 and an EL34)to super hard rock overdriven to bluesy kind of Stevie Ray tone just by changing pickup selection and volume knob on the guitar. If you have been using an amp with a drive channel or a clean amp and distortion pedal you should be prepared to have to get used to this amp and spend a lot of time experimenting with it because you wont use this amp the same way that you used your other amp (I know this from experience)this amp is the most touch sensitive amp that Ive ever played Ive even put a compressor in front of it just in case I get a little heavy handed on accident (the les paul pickups are really hot)

So far ive only used this amp around the house and through one long cranked brutal recording session, will be gigging soon and do not expect any problems. Holds up wonderfully.

I wish that I could go better than a 10 in this category because these guys are top notch. I have contacted them on numerous occasions before and after buying this amp to ask questions and they are wonderful, they respond quickly and give helpful answers. This is definitely one of the best pars of owning this amp.

This amp is wonderful, I also have a 2x12 cabinet and I am totally impressed with THD stuff. I love the versatility and customer service. I really must stress that even though this amp is a simple one channel amp that you really do have to find its sweet spot and experiment with it. Also just like any other amp before you make a decision on its tone consider the room that you are playing in. I had trouble with tone in my living room (acoustics like a cardboard box) but when I played it in just a little more lively room it was awesome, now I am hooked. Feel free to email any questions about this amp.

Pure Class A Head. Can mix and match just about any combination of pre and power tubes. Built in Hotplate.effects loop line out etc. Just about everything that you'll ever need its right here. The ability to alter the gains of the pre tubes and changing between any combination of KT66/6L6/EL34/6V6/EL84(with a univalve yellowjacket)will help you uncover just about any amp tone I can think of. Its great fun too.

Listen up. This is without any shadow of a doubt, the best amp I have ever ever owned. If like me you have spent your time frustratingly searching out your the perfect tone and find that even with the big name amps and guitars and expensive boutique pedals that tone is just slightly out of reach, this amp will take you there and probably beyond. Its a strange feeling when you realise the search is over!! I also have a mesa tremoverb and heartbreaker, 2 old Marshall heads and a old vox AC30, but all don't quite give you the sheer excitement and feel of this amp. With my band, the Bivalve has revolutionised our recordings and our live sound.I use selection of stock 1990s gibsons and US fenders. Nothing vintage!
The touch sensitivity and way the guitar volume effects it is a revelation. Clean sounds are chiming and slightly compressed kinda like gilmour on shine on you crazy diamond, while the high gain settings well outstrip my marshalls and mesas with breath to spare. W(ith the occasional keeley pedal in front) It cuts through the band mix in a way that marshalls and mesas often dont. They sound good played alone, but add the band and they kinda get lost. The THD kills the dual recs hand down if you wind it up with a java boost or a fuzz head in front!

My first one developed a gradual sonic fault after about a year. The difficulty with such a perfect amp like this is that the slightest niggle is immediately audible. They said it could be a transformer issue. But get this...THD UK (Synergy) immediately sorted me out a brand new replacement and even had Andy Marshall contact me from the US to sort out what could be wrong as it is such a rare occurence.

My replacement needless to say is a stunning bit of kit

See above..Truly exceptional

THD (and Robert keeley and Z Vex) should give all other music companies lessons in customer care. They are the genuine article. I guess its because they are as proud of their products when they build em as we are when we play em.

I now have a THD univalve, bivalve, 2 hotplates, 6 yellowjackets. THD really do help me play my music and get that real sonic thrill that we all spend our lives and money trying to find. If you can play well and care about tone, I defy you not to sound and play even better through a Bivalve or univalve.
I know I sound like a THD rep, but I have genuinely stopped looking for pedals and amps in shops now the THDs and Robert keeley pedals are are here to stay...now as for guitars....

i bought this amp on ebay. i play in an original melodic rock band. amp does a decent plexi sound but is not as convincing as my cage amp. the features are decent. the thd atten. is a nice feature for some, but i hate the way it affects the tone. too many artifical sounding eq bumps for me. just a single channel amp. wish you could have the ability to a/b less and more features or combine both like an AC-30. plenty enough power. easy access to change tubes, but i like to retube and get on with it.

I play mostly solidbodies(les paul, guild, anderson cobra) with duncan jb's. the amp sounds are just not happening for me. not enough clean headroom just sounded very harsh and clacky on less. it was running through a bogner 4x12 with vintage 30's. the more channel was a little buzzy. i switched to lower gain preamp tubes and got better results but still the sound was not tight enough. i was trying to retire my jcm800 for a lower watt amp. i guess i have been spoiled. but with all the positive things i have heard about the amp i gave it a try. i love to dial in eq and i just could not get this amp to blow my socks off like everyone else.

was very reliable. you can definitely count on this amp in this department. never broke down on me and i played out with it 3 nights a week for 8 months, before i sold it on ebay.

n/a

i have been playing for 23 years. i own a smf 30 watter, cage 18/00 series, marshall jcm800. used to own a mesa heartbreaker, ac-30, various fender combos, marshall heads. i would not say this amp is close to the amps i currently have especially considering the high price. my smf was $850 used on ebay and it's variety kills. the bv is a well made amp. reliability was never a problem, i just think people are so jacked that you can change tubes on the fly that they are wigging out. the atten. was worthless for me just did not like how it compressed the sound and re-eq'd my speakers natural sound. my overall rating is considering price tag and other amps in the price range.

Just as described below. My only real gripe is having to use a reverb pedal when playing at home. My Princeton has spoilt me. The single channel is no problem for me, as it's pretty easy to manipulate the overdrive level with the guitar volume. I play mostly Blues with some Jazz and Rock here and there and the BiValve gives me exactly what I want. Now, you do have to spend some time figuring out what tubes sound the best in what combinations, but that's all part of the fun. I'm a constant tweaker of tone, so I never settle on one setup and it just seems to get better.

I play a Lonestar Strat in open G for slide, a new American Deluxe QMT SSH, and a '72 Telecaster. All sound very good through the BV, but the Tele is a little weak in comparison to the Strats in most every way. The singles and Humbuckers sound equally good on the Strats, and the new S1 switching is even more useful with the BV than any other amp I've got. Giving really smooth and full tones that sound nothing like a normal Fender. My Deville and JCM900 don't seem to fair as well with the S1 options. The clean tones are rich and smooth, and the overdrive can be anywhere from a very slight creamy breakup on chords to full blown saturation that's way too much for me. However, it's all very dependant upon the tube selection and amp settings. There are several ways to alter the tone, but it's not hard at all to find great sounds in the BiValve. I'm giving it a 10 since it nearly equals my '68 Princeton Reverb (which is one, if not the, best sounding amp I've ever heard) in clean tones, and blows it away in the distortion and versatility catagories. It really does sound awesome!

Haven't had it too long, but it seems to be built like a tank. Spare tubes and fuses are always a good idea at a gig though.

Never dealt with THD, but I bought mine online from Steve's Music up in NY. Wonderful customer service from Steve, and a truely outstanding price!

I'm a full time musician and guitar instructor with about 10 years experience. I currently have a mod'ed Hot Rod Deville, a 100w JCM900 w/1960a cab with two Vintage 30's and two G12T75's, and my beloved '68 Princeton Reverb which I play through the Marshall cab most of the time. The BiValve covers all that ground with superior tone and much more flexablilty. If I need to play a big outdoor gig, I've got the Marshall. For everything else the BiValve does a better job than any amp I've played through.

The bottom line is that the BiValve is truely a superior tone machine that allows you to sculpt your own personal sound with relative ease. It's also an INCREDIBLE deal and just super fun to play with!

The BiValve has some very nice features such as a built in hotplate, a hi/lo voltage switch an efx loop and and a variable line out. It also has the ability to change tube types on the fly with no rebiasing. Since it is only a single channel amp, it does have some limitations for live use. For this reason I give it an 8.

I am currently using the BiValve to drive a Bogner 4x12 cabinet. My main guitar is a PRS McCarty. Tubes are 2 EL34 with 2 12ax7's. Because I have been primarily a Marshall player my whole life, I am in love with the 70's classic rock sound(tone). The BiValve can nail those sounds perfectly. Whats better, it can get them at a much lower volume thanks to the built in hot plate and Hi/Lo voltage switch. It also has the ability to get some fairly high gain sounds. Not metal,but more of a hot rodded plexi sound. My favorite setting for the amp is the "More" channel on Lo-V with the hot plate engaged. I dial it in for a good crunch tone and then use a FullDrive 2 for my leads. It sounds killer.
Even though the BiValve is single channel it is not a one trick pony amp. Using the "less" input, you can dial in some great clean tones. Actually the more I use the BiValve the more I discover its versatility. It is a very fun amp to play.

So far no issues. The amp is built extremely well. Of course being a tube amp you always want to bring spare tubes to a gig.

I have not had a need to contact THD.

Overall I give the BiValve a big thumbs up. For home and studio use it is very versatile. The tone is awesome for both clean and distorted sounds. For live use it has some limitations if you need to switch between a clean sound and distorted sound on the fly. It can do both very well but it requires some knob tweeking. I will say this, the 30 watts is plenty loud so dont worry about it being under powered. Also, I think they are a great value in the used amp market.

Pretty versatile amp for studio use. Live it is more of a one tone at a time type of deal, since the two inputs differ drastically in volume. The features are simple, but very useful. Definately much more flexible than the Univalve. You can use one tube in this amp and it sounds about 85-90% like a UniValve which is great for quieter recording, yet pop in two El34s and you are gig ready. I do wish you could switch between cleaner and dirty tones on the fly, other than that there is nothing I'd really add to this amp.

Great sounds are available in abundance with this amp. I do find that it can be sensitive to what guitar you use as well as speakers. To me, the preamp tubes make more of a tonal difference than the power tubes. Certain guitars seem to like certain tubes and settings, while other guitars may not, so I would say this is not a plug and play amp even though it is a simple layout. Some people may get great tones right off the bat, others may need to tweak a while, but they are in there. Great for blues, country, rock and hard-rock, maybe even lighter metal. Not a ton of clean headroom, I find it breaks up just a hair when set clean for gigs, but this also depends on your speaker setup. I had a Univalve for about a year and loved it, but sold it and bought the BiValve to get a more gig friendly amp. If you can afford the step up, the BiValve is a better amp to get, since it is so much more flexible than the UniValve.

Never had a problem. THD amps are built like tanks so I have gigged without a backup. Even when I use other amps, this is in the car as a backup, since I am confident it will always deliver.

Best customer support I have ever seen, bar none. Ed Degenaro is around on many internet forums, answers lots of questions and seems to have the patience of a saint.

I've been playing over twenty years. I got this amp mainly to use in home recording, but I wanted more power than the UniValve if I ever needed it. I don't know if I would replace it, since I also have a Flexi-50, but I would be very upset if it were stolen. It doesn't do everything, but what it does do is enough for me. If you want a solid, reliable great sounding amp without a lot of bells and whistles, check one of these out.

Has every feature I could think of ...exept the possibility to switch between "more" or "less" channels and effect-loop on the fly.

I use this amp as a practice amp. Play mostly `60. `70 and `80 rock and hard rock. This amp sounds right for me and it is just powerful enough so that you can play it wide open most of the time to get the pushed, saturated sound. Pure Tone !

Les Paul Custom with stock pickups works best for me. This amp is never noisy, it just sound better the more you crank it !

The amp can do many sounds from early saturated buttery thick sounds (6V6) to more chunky crunch (E34L, EL34) to less power distorted more headroomish (6550, 6L6).

It also has a complexity and warmth to its sound rarely seen.

I have never made a 4X12 cab scream with this amp (a scream for help, maybe.) A more suitable combination is a 2X12" or 1X12" G12H 30W or alnicos will work fine !

The clean channel can go muddy on high volumes depending on the power-tubes, but it always sound great.

You will not have a tight bottom end at higher volumes as the bottom end always is a difficult load for the amp that demands wattage.

I believe most people will discover many enjoyable sounds in this amp.

Never had any trouble.

Don`t know

Been playing for 12 years. If it were stolen I would consider a flexi 50 because of the additional power, nothing else. If the flexi 50 were down on tone or general sound quality, I would still go with the Bivalve.
There is just something I love about this amp, probably its ability to add something of a feeling or state which helps get across your musical message and feel.

This tube amp is Class A, single channel, and very versatile. It's self biasing, so you can use a wide array of power tubes without having to make your amp tech rich. The other reviewers cover the "features" of this amp pretty well, so I won't waste your time. I will say it's got some very useful extras (effects loop, line out) that don't rob your tone. The built-in Hotplate attenuator works well when used lightly. If you attenuate too much, you lose tone. Like all tube amps, this one sounds best pushed. This amp is listed as 30 watts (varies according to tubes used), but don't let that fool you. This amp can make a 4X12 scream.

My main guitar is a Wolfgang, but I play a bunch of different guitars through this amp and they all sound good. It really brings out the character of each guitar. This amp can do anything from Jazz to heavy Rock depending on the tubes and guitar you choose. It has a huge amount of gain, but I wouldn't use it for 7-string or baritone nu-metal.
I think the single most important thing you can do when you first get this amp is start with a lower gain pre-amp tube in the driver position (I really like a JAN GE 5751. Mullard 12AT7 is good too). After you play a bunch of different tubes through this amp, you really get to know the flavor of each tube and how to mix and match specific tubes for any sound you're looking for. Even though Vintage tubes do tend to sound a little better (and last longer), this amp still sounds great with modern production tubes. I love this amp in the studio. Why settle for one of those "modeling amps", when you can have the REAL thing?!

All THD products are extremely well built. I've had my THD Hotplate for years and never had any problems. I expect to get the same performance from my BiValve.

Never dealt with them, but after doing a lot of digging on the web, I haven't heard any complaints. You can't say that about most companies.

I've been playing for 25 years and used/owned a lot of gear. My main rig is a Soldano Decatone. I've been salvaging Vintage tubes for years, so the self biasing feature of the BiValve is what first drew my attention. I liked the idea of putting all my mismatched tubes to use. After hearing the wide range of tones this amp will produce (with vintage OR modern tubes), I realized you don't have to be a tube monger to love this amp.
I do wish this amp could be switched between the "less" and "more" input. That would make it a little more versatile for live use. If you want REAL tube tone in lots of different flavors, this is your amp.

Enough said. Great stand alone amp or using as a preamp for other amps. Basic and versatile. Not too complicated but you can make it work for a ton of different needs that come up. My favorite feature is the fact you can go from 30W to 15W by pulling an output tube. The hotplate is useful but I never use it b/c my ears hear a difference when it is on. Channel switching would be nice but I would not likely use it with my current setup.
My tech knows more about tubes and the specifics than I, so when we are in some city, he stops and somehow finds great hard to find tubes. So we have a nice collection. I give him the ability to change at will. So we do a lot experimenting and we actually keep getting more specialized and better results as we go along which makes it exciting for he and I. That is a feature in other amps that would be a pain in the ass, but with these amps you just pop the top off and have at it. So for me it is a ten.

I play in a semi-national band, touring 3-5 days a week. We play anywhere from 100 person clubs in NYC to larger theatre-sized venues in our markets. Our style from what I am told falls between Our Lady Peace/Counting Crows/Catherine Wheel. This is simply one of the best amps I own. I use this in conjunction with the univalve (as a preamp/dummy load) using a GCX switcher to place the univalve in and out of line. An Axess Electronics BS2 splits the Univalve feed into the Bivalve and a Vox AC30. It is running a Mesa 4x12 w/ Vintage 30's. The great thing about the Bivalve is the ability to roll the volume off of your guitar and get very complex crunch/clean overtones. I am playing on Les Pauls and SGs w/Fralin pickups and it really adds something special to the overdone Marshall/Mesa thing. I run this amp slightly distorted allowing me to have a clean sound when I play soft and a crunch when I attack harder.

The amp sounds are complex and broad. It can sound like whatever amp you have played on, trust me. I get a overdriven Vox Top Boost sound out of it. Could be the tubes and the way I use it, but when I run the Univalve through it, is straight power amp distorion. Cuts through the mix and has very defined frequencies. It makes me play better b/c there is no moosh to hide behind. It is a very articulate sounding amp. I have done the Marshall/Mesa/Fender thing for years, but wanted a new direction for my band and my sound in particular. Well I am glad I found the Univalve 3 years ago, b/c it pointed me to this amp. For real touring musicians it is great b/c when we play smaller club dates I switch to 15W and when we play our theatre dates I can just crank it.

Reacts great with any array of pedals. I have used the effects loop and it is good. I just prefer to run everything in line. I give it a 9 for the many useful sounds you can achieve with it at the turn of a knob. Very reactive tone knobs.

Here is the best part of the amp. Great company, great personal skills, and great designs. I have a backup to everything just in case. But with this and the univalve I bring extra tubes on the road and I really never have to worry about anything. I can not honestly say that about any amp I have ever played used. When we go out and are not coming to home base for another 3-4 months reliability is more important than anything. Yes I use a Vox AC30 too, but we have to bring two others AC30s to get us through one of those 3-4 month tours. That is a pain in the neck and was in our pocketbook.

Great! These guys are class acts. When you find a company like this you stick to their products. For me they are up there with the Robert Keeley's of the world.

Been playing for about 10 years. I have honestly had a lot of amps and gear (Marshall DSL-50, Marshall Master Head, Marshall Super Lead, Laney VC-50, Orange Combo, Fender Dual Showman, Fender Bassman Heads, Mesa Boogie Maverick, Mesa Tremoverb Head, Matchless DC-30 (stolen), Mesa Triaxis, Marshall JMP-1...etc) This is the one amp that I will always use on stage and in the studio. I will always have another flavor of amp with me to add to the sound, but this is a must for me. I am fortunately in a position to influence some people and I always point them towards this and the Univalve.

Its hard to rate this catagory. I play vintage-type amps exclusively. Compared to most vintage-type amps this thing is packed with features but for someone who's used to channel switching its not that flexable. Yet if thats your complaint I think your missing the point of amps like this. I wish it had a preamp circuit closer to the classic british design (normal and bright volumes, Bass, Mid, Treb) but it has its own thing and honestly I cant knock this amp in any way in the feature dept. Its crazy but I think more then anything else I love its size. Just my marshall heads alone take up so much space. Plexi's are huge. HiWatts are huge. If I set the THD cab Vertically (on its side) and set the BV on it I have a little mini stack like those old Sovtek Midget stacks. But this rig has huge tone. The tube flexability is obviously a big deal. Prepare to spend some $$$ on tubes if you dont have a collection. That can be fun though. Tweakage and trials. If you like that sort of thing.

Ill say more then anything else I like the features of this amp. A 10 in this catagory says versatile. In a modern sense I guess its not but to the vintage/boutique world it really is.

I like Les Pauls. I like PAF type pickups.

For people reading here trying to figure out what the sound is of the BV Ill say it sounds closest to early marshall sounds. Its hard to pinpoint it as one thing but it seems to really be in that early marshall heritage. Not Vox or fender as much as marshall. Youll find an accurate ACDC and Rush way before youll find Brian May or SRV. Not to say they cant be found but its easy to dial in those sounds right away, especially with the stock EL34's. Its like a Metal Panel Plexi with a little bit of Vox and Bassman thrown in. Its definitly got a high bite to it like a 70s plexi. An accentuated higher range that can seem shrill or can be on certain settings. Theres ways to defeat that and get real warm or even brown tones with this amp.

Vintage style amps like this just have such a unique and amazing tone. They chime. You can hear all kinds of overtones when you hit an open E. It makes all modern amps and distortion pedals and all that stuff sound and feel the same. The amp's unforgiving. If you have bad technique youll sound bad with this amp. On the other hand if you have good technique youll find this amp very rewarding.

Heres a few things I found with the tone. Im a huge marshall fan so I tried the hardest to nail those tones. Ive gotten very good Vox at times as well. Ive had a harder time getting fender but Ill admit I havent tried much at all. I also focus more in the crunch tones then clean tones.

One thing with old marshalls is that its very common, when trying to get a tight, high-gain tone, to dime the treble and mid and leave the bass at like 2 or 0. The tone controls of old amps seem to interact more with the tone of the amp. Modern amps eq's seem like stereo eq's. They only adjust the loudness of the frequencies. Setting the bass on 0 and the treble on 10 would make a modern amp sound like its inside a tin can. On old marshalls, and the BV, the tone controls seem to alter the frequency responce more. Their a bit more interactive. When the bass is up high the gain is very loose and tubby. When its low the gain is tight and chunky. I think with the BV if you want a cleaner or bluesier tone you can have the bass higher but for a little more gain and a tighter tone you want to dime the treble, or at least set it to 12o'clock or higher, and turn the bass off. It doesnt make the amp sound suddenly like it hass no bass. Or make the treble suddenly tear your head off. It just makes the overall bass responce tighter and thicker actually. Its very common with old amps to run the tone controls in that way. For a brown sound with this amp I think its a necesity. I can get a very warm and soft yet tight, EVH-like sound were you really get a nice thick "chunk" when playing those mutes low strings.

The Attitude is a weird control. I like to keep it at 10 to get the most "plexi" out of it. It also tightens up the gain and makes the amp seem to have more gain when its up. I usually only turn it down when Im going for a cleaner tone.

One thing about getting more gain with the BV. Using a 12ax7 in the driver only makes life harder. With 2 12ax7's in this amp and the volume dimed its a very loose, out of control gain. Fuzzy and feedbacky. I like to use a 6189 (12DW7) in the driver to tame that gain and I can get a tighter, higher, smoother and warmer gain as a result. The 6189 also tames the harsh top inherent in this amp. a 6189 may be a lower gain tube but its more useable gain. So I can actually turn the volume up to 10 and know the gain will be smoother, chunkier and tight.

With these few things I can get a really nice, ballsy crunch. I can also get a great brown sound. Obviously to get more of a classic plexi crunch sound it should be on HiV and to approximate the EVH sound it should be LoV. Or better yet. Leave it on high and use an actual variac.

I want to stress another thing Ive learned. Moreso with this amp then with others Ive played, the speakers make a

All I can say is they answer emails in 1 to 2 days.

This is a review I have been meaning to contribute for a while. I've had this BiValve for almost a year now, but I wanted to wait until I recorded with it and had planty of time to test it out to give a fair honest review. My bivalve is 2002, #141. All the features have been previously listed but I will say that the controls are very simple, intuitive and musical. Every knob and switch (of which there are not many) is very useful, and the only thing I wish it had is a midrange control. Although I love the midrange content in it's natural tone, I would like to be able to dial in more midrangey crunch for some things. overall, though I'd say the amp is very well designed and versatile. Although I do also wish (really wish) it had the ability to use an ABY box to switch between low and high gain inputs. This would make a live situation much easier as the amp only has one tone instantly accessible. and I can't exactly afford to have two of them.

This amp has some incredible sounds and is extremely versatile. Much more than I thought when I bought it. When reading the glowing review, I doubted this amp could do all that previous reviews said it could, but upon hearing it I was sold. The true test is that when I bought it, my musical style was different, and having changed styles, the amp had adapted itself perfectly to my new playing.
OKay, well if anyone cares, my rig consists of a stock lefty G&L asat special semi-hollow w/ soapbar style pickups, or a heavily modified lefty Gibson SG special w/ seymour duncan pickups (which btw will soon be changed to joe bardens). My pedalboard is simple, I run either guitar into a VHT valvulator line driver (a buffer that converts your signal to low inpedance to save your signal from tone suck caused by long cables and pedals), a snarling dogs blues bawls wah, a fulltone fat boost, and a boss tuner and noise reduction pedal. I run the bivalve into a THD 2x12 cabinet which also sounds great.
As I mentioned earlier when I bought this amp I played a different style of music. I played Heavy Rock along the lines of Tool and Soundgarden. The belavle sounded great for this and thats initially why I bought it, for the massive overdrive sounds. I put of pair of 5881's in it along with some high gain 12az7's and I could get big massive grind. Now, my style has changed to a more Rock/Pop/Blues/Spacey kind of thing that way more vintage sounding. I can use an EL34/6L6 combination for clean dirty, or a pair of EL34's for crunch and it has great clarity and punch. With different combinations of power tubes (EL34, 5881, 6L6gc, KT66) and a few different variations of 12ax7 and 12at7 preamp tubes I can dial in everything from really clean, to egde of dirt on the low gain input and blues rock to ballsy crunch to singing lead to massive distrortion on the high gain input. I really am quite impress with the versatiity. I wouldnt really call this amp truly high gain, but thats good for me because i don't want rectifier tone. it also doens't have as much clean headroom as a fender but I have a fender amp for that.
This amp records really well and cuts through the mix great. it's versatility is welcome in the studio and it isn't noisy at all. I rarely use the noise reduction because the light bulb tends to burn out fairly quickly and it has a slightly negative effect on the tone. Oh, and in case you think 30 watts isn't loud enough, try running this thing without the attenuator on, it'll rip your head off! More than loud enough to keep up with a band practice. I'm sure you could use it live and it would be more thanloud enough as well, but any club you play at with a decent seating size will mic the amp anyways and tell you to turn down. I think 30 watts is plenty and more than that is just silly unless you need crazy clean headroom.
The hot plate attenuator does a great job of reducing the volume without affecting the tone, but be forewarned: don't expect to be able to run this amp at bedroom volumes and have massive sounding tone. The reason for this is the speakers, not the amp. When a speaker (especially an 80 watt celestion like what comes in the thd cab) is not given a lot of power, it won't sound good. All the distortion in the world won't sound huge without good speaker break up. For this reason I almost prefer to run the amp with the attenuator off at low volumes. It has way more harmonic content that way and a bit more treble as well. So, in my opinion, the attenuator is great, but you can't create cranked amp unless you crank an amp.
When I play this amp live, I am probably going to run the amp at full power on the high gain input with the volume at abot 1/4 (which is still plenty lound and decently distorted) and use a good tube distortion pedal (like an SIB varidrive) to get my overdrive sounds at a reasonable volume. Although the distortion on the amp is incredible, I need to versatility of switching between clean/dirty

Okay, check this out. This amp is extremely well built and is very dependable. But after having mine for about 8 months, it just uyp and died one day. Just suddently in the middle of my playing, the sound just cut out and was reduced to a mild fizle. I thought it might be a tube or a fuse but it wasn't. I called THD and Ed Gegenero (very nice guy) told me he thought it was a cold solder joint that had come loose and I should send it in for servicing. I was nervous about this because I needed to record with it in less than a month and I've heard how long some companies take to service thier equipment. But I sent it in and had it back in well less than 2 weeks. Ed kept in contact with me via phone and was very helpful. They even sent it back to me with a brand new set of power amp tubes at no charge! The amp has worked perfectly since. one time I though it had died again (this problem turned out to be a George L's cable that I had improperly connected and subsequently came loose cutting in and out) and I called and spoke to Ed again. He said to check everything including the tubes and if the amp had a true problem that I could send it back and he would send me a brand new one. SO it's clear that they really stand behind their product. I would gig this amp without a backup, although not without some spare tubes and fuses just in case. Although I've never personally blown a fuse, some other reviewers indicate this does happen.

As mentioned before THD is great to deal with. They are super helpful and nice and they really take time to tlak to you and answer all your questions. All of my many stupid e-mails to them have been answered withon 2 days. They really stand behind their products and with good reason. They are the best. Did I mention that they were willing to replace my amp for free if it broke down a second time?!?!

I have been playing about 5 years. I have gone through many changes in stlye and gear over this time. I started with a small combo then moved to a marshall half stack. Then I moved to a rack system tpe preamp/poweramp setup. That being too complicated to use all the time I went to a large fender Blues deville combo amp, and then to this bivalve setup. It's small enough to lug around for practice (although heavy as hell!) and it sund amazing without having 6 channels and 37 knobs and switches. It's simple and fun and inspiring to play. Before buying this amp I tested a few other amps as well as researched lots of other "boutique" amps. This one had the best features for the best price as well as a solid company standing behind it. a rare find. The only other amp I've tested that sounds this good is the bad cat hotcat at about twice the price. I still may buy the hotcat because of the ease of switching inputs between clean and dirty for ease of use live, but for the price I paid the bivalve can't be beat.
Would I buy it again? Yeah I think so. I am always experimenting with tone so I think I will always be trying new amps, but I have become very attached to the tone I get from this amp. Everytime I play it I feel inspired to create, and I think thats what a great amp does. It not only sounds good, but it feels good too.
If this amp had a midrange control and on the fly switching it would get a 10.

My BiValve is a 2003 and it suits my style of music perfectly. I play Blues, Classic Rock, Rock, Hard Rock, Alternative Rock and a little metal. This is a 30 watt single channel class A amp. It does have an effects loop (unlike the Univalve). Don't think a 30 watt is loud ? Go try one ! I really thought that I would try some tubes and settle into a particular combination and I would stick with it....but nooooooooooo....I actually change tubes all the time based on my mood.

My favorite tubes in it are EL34 types and my favorite preamp tubes in it are NOS mullard 12AT7's and NOS baldwin 12AT7's ( I snagged some of these Baldwins for $5.00 a piece...talk about a good value...extremely low noice / microphonics).

I also like so far the 6V6's / 6L6GC's / NOS 6L6's / 6550's. Each yield a different sound or attribute which the BiValve can capitalize on. It is so easy to swap tubes...Why not put in some 6550's when you need some clean head room or some loud tight compressed distortion with crisp highs. Why not slap it some EL34's to get a thick low end and one of my favorite 'power tube' distortions.

I like this amp just the way it is. Some people complain that the unit doesnt have built in reverb. This thing sounds so good, I don't miss reverb. The tone is so thick and true.

I am a Gibson Double humbucker kind of guy. I mainly play a Les Paul Standard, Gibson SG and a 1970 Guild S-100 thru the amp. The Les Paul sounds the best thru the amp as far as 'Tone'. This Amp with a my Les Paul makes for a really thick sound. If you like a truly overdriven sound (not that fuzzy stuff they call overdrive)this is the amp ! The amp has built in noice suppression that you can turn on or off. The amp has a bulit in hotplate so you can crank up the tubes but turn down the volume ! This is a really great feature, however, the more volume you soak up with the hotplate the less you will like the sound. Cut the volume half-way even 2/3's and it still sounds good....start going lower and the tone loses it's luster. You can't expect to get that thickness if you rob 90% of the volume. There is also a low-v / high-v switch for controlling the plate voltage on the tube to get increased volume...I personally prefer the low-v setting. There are two input jacks labeled 'more' or 'less'. The less is better for clean sound and the more is better for overdriven sounds. I could go on and on about this amp.

Check out http://www.univalve.net/forums/ for univalve / bivalve info / thoughts / opinions provided by other users.

Yes I feel I can depend on it. Backup tubes and fuses are probably all that one needs. A backup is always a good thing just in case something happened to the BiValve that was outside THD's control....like the bouncer smashed it several times with a baseball bat because you were hitting on his girlfriend !...I dont think the unit would fail on it's own accord. Any Questions ?

Doesnt get any better.

I have called asking questions a couple of times and THD's staff has always been helpful and courteous. Ed pointed me to a helpful forum:

http://www.univalve.net/forums/

Ed and Andy have posted alot of info about the amp on this forum and it appears they try to help all that need it. I have tried getting support from Fender and Crate and I would not call it support !

These guys are fantastic !

I don't know what the warranty is for this amp, but it is the most solid piece of equipment I own. It is built like a tank. If I ever have a problem with the amp, I am pretty sure THD will exceed my expectations.

I have been playing guitar for 15 years. I have a small home studio and some other amps, but nothing that compares to the BiValve. The BiValve is my first expensive amp and it is worth every penny. Expensive is a relative term. It is expensive compared to my Peavey Classic 30 or Crate VC50 2x12 combo. It is not that expensive when you compare it to some of the other makes & models on the market. If it was stolen, State Farm better Damn well buy me another one !

Why did I chose a BiValve over other amps in this price range ?

Besides the fact that it sounds fantastic !

1) The tube flexibility
2) The built in attenuator
3) The built in dummy load & variable line out
4) Attention to detail
5) Small footprint (nice for my cramped home studio)


It will probably take me years to explore all of the possible sounds that I can get from this amp...but I love it already.

This is an update to an earlier post. Have obtained 2 Mullard EL34-XF1 tubes along with 2 Mullard 12AX7 tubes. What a sound. You have to experience it to believe it. I use a Sparkle Drive or my TS9 to push the front end a little and it just sings. I am after a Blackmore/Schenker/Roth type of sound. The natural harmonics are incredible. Also have started using a set of KT66's I was able to dig up. Cleaner tone. Great "punch". Fairly loud. Very sensitive to attack.

Still experimenting. A word of caution though...Those with G.A.S. may aquire a new weaknes...T.A.S. tube aquisition syndrome!

Bought new in June 2002, ser#0069. On the surface, this may seem to be a simple, single channel tube amp. However, this is probably the most flexible amp I've used. Details are included in posts below...I can only say that every knob and switch is really useful.

Right now I'm using this with a '60s reissue Strat, and it sounds great. I'm using it in the more channel with Philips 5814A and Magnavox 12DW7 preamp tubes, and Philips 7581 and GE 6550 output tubes, for a cleaner sound with more headroom. With the volume pushing about 3/4 this moves from a more Fender clean to more of a Vox feel. With two 12AX7s and output tubes that clip faster (ex. EL34), it's got a lot of really toneful gain. Personally, I love the tone of this amp, and think that most will agree, although I don't hear it suiting a scooped metal lover. As others have said, this amp has the complexity and tone in a class with amps costing 2 and 3 times more.

I've been using this regularly without backup and have had no problems.

Excellent! Quick, courteous, knowledgeable.

It sounds and "feels" phenomenal, is very portable (but a little heavy), incredibly flexible, and very dependable.

Had the amp about 6 months - #125. Features noted below. I can't overstate the utility of the line out - you can use it to drive an effects processor/slave amp for a stunning wet/dry setup, or while recording, you can record the line-out in addition to miking the cab and mix the tracks to taste. Channel-switching and on-board reverb are about the only things I can think to add. I don't miss the reverb (I prefer studio-quality digital 'verbs to springs anyway), but the ability to switch between clean and dirty sounds on the fly would be useful for live situations.

Rig is thus: Fender American Deluxe Tele/Fender American Strat Plus/Paul Reed Smith Custom-24 -> BJFE Baby Pink Boost -> Fulltone Clyde Deluxe Wah -> SIB Varidrive -> Maxon OD808 -> BiValve Head -> THD 2x12 Cabinet. I run the line-out of the BiValve into a t.c. electronic G-Major, then into a slave amp for a wet/dry setup. I primarily use the BiValve for recording, and playing at home and in small venues.

The BiValve is simply the best-sounding amp I've ever played through. Certain amps may have an edge in one area or another, but the overall tone of the BiValve, coupled with the tonal flexibility of different tubes, control settings, and overall volume (with the built-in attenuator) makes this a studio dream machine. Wonderful clean tones, great high-gain Marshall-esque tones, and the best in-between crunch tones I've ever heard. This amp wasn't really made with ultra-gain metal tones in mind - you can get pretty close, but you might find you need some sort of overdrive pedal to get you there. Thirty Class-A watts is plenty loud for most venues.

Construction is top-notch. THD has a stellar reputation. That being said, I haven't had it long enough for my comment to have weight. I don't expect any problems, and I expect any problems I do have to be handled well (see below...) Would gig without a backup, although I would bring some spare tubes and fuses.

Absolutely top-notch. THD's reputation is well-earned in this area. If you want other opinions, visit www.univalve.net and read...

Been playing 16 years, mix of jazz, rock, blues, etc. Have owned a fair amount of gear and played through a lot of other stuff. I would replace this amp in a heartbeat. It's so easy to lose yourself when playing through this amp - the sound is that good. There are a lot of boutique amps out there, many of them outstanding products, most of them focused on one tonal area or another. The BiValve is a chameleon, able to adapt itself to almost any situation. I have not encountered any other product with the tonal quality and flexibility of the BiValve. I'm sold...

Class A all tube amp with built in attenuator as described by others ... it is very heavy ...

Probably the best sounding amp at any price anywhere: sounds very 3 dimensional and rich and basically beyond words ... after hearing this baby you will never touch digital toys :-)

It was brand new when I tested :-)

Nice guys at THD.

In the end I didn't buy it as it is very heavy and if I sclepp that and also a cabinet that's too much ... instead I bought the THD HOTPLATE attenuator that I use with my LIGHT combo (35lbs) Divine sounding class A 3 channel all tube $650 Ashdown Peacemaker 40 - Ashdown now sings and as it is class A the sound is almost as good as the THD BiValve and I have several channels etc ...

If I were younger and wanted THE TONE I would buy either this head or Peacemaker 50 head or Cornford Hellcat; the latter is ost expensive ($1499) ... but under $1k my Peacemaker rules ...

This is a "follow-up" review to my earlier post. I made a mistake in
calling the two inputs on the Bivalve "Rock" & "Roll." On the Bivalve, the two inputs are "More" & "Less." Other than that, I enjoy this amp more & more every time I play it!!

The amp is serial number 108. I play a mixture of blues, R&B and 1960's-70's rock and this amp does them all well. I've owned/played just about every "cool" amp out there over the years (including Marshall, vintage Fenders, Orange, etc) and the BiValve has the richest/fattest tone of them all! I don't really miss the reverb that much, but if Andy added it, he'd have a real winner! The 30 watts is plenty of power, in fact I am currently using two "JAN" 6V6GTs in it (to reduce power for practice sessions). Will run 2 RCA 6L6GTs for gig situations. Am running the amp thru a single 12" Celestion G12T-75 in a closed back cab...would love to have one of the 2X12 THD cabs but can't currently afford it! May also run the amp thru a 4X10 Slant Front Marshall Cab I can purchase for cheap!

Using mainly a Gibson '59 Reissue Les Paul Sunburst Standard with the "Burstbucker" pickups and lightweight stop tailpiece...sounds great with many of the old classic overtones that made the '59 Burst so famous...amp is very quiet and can generate a load of different sounds including the "full-tilt" boogie (ZZ Top sound). It also generates a nice crunchy rhythm sound on the "more" channel w/ the volume at about 9 or 10 o'clock...I use various OD pedals for taking solos...

no problems and don't expect any...this thing is built like a battleship!

responses from THD have been very timely!

I love this amp...it is a little heavy to lug around (but not as bad as a Marshall Super Lead 100! I think it is a wonderful addition to any "tone-hound's arsenal!"

The Bivalve gives the player so much flexibility: between changing tube types(and not worrying about biasing), and the two channels "Rock" & "Roll," & the built in attenuator, the player has a full pallette of tonal colors to "paint/play" with.

Also, the effects loop is a benefit, I run my tube reverb through it.

My Bilve is #54, and I've had it about a month. I play mostly blues and slide, and the Bivalve has enough power for me to gig with.

I use all P90 pickup style guitars, and they sound great. Between using the "Rock" or "Roll" channels, using the attenuator, and then trying different power tube and preamp tube combinations, if one can't get the tone they're looking for I'd be quite suprised!!

Moreover, the Bivalve has allowed me to delete two pedals from my pedal board. I have no need for my Analog Man Compressor or my TS9. I can get the tone I need from the Bivalve ITSELF!

Also, this is a quiet amp. I've only played it throught my THD 2x12 cab, but it is quiet. If I'm not playing, there's no noise coming out of the amp!

Built like a ROCK! Looks solid.

I've contacted THD by phone and email, and they've been quite helpful and friendly.

I've been playing 30 years now, mostly acoustic country blues and slide.
So when I play electric, I'm looking for a good fat, clear, slide tone.
I had a Victoria 20112 that I sold for the BiValve. The BiValve gives me more clean headroom, and like I've stated previously, the amp gives the player so mucjh flexibility in shaping a tone it's hard for me to imagine not being satisfied with it. My tone quest for amplification has ended, and if my BiValve was lost or stolen I'd be pissed and replace it ASAP!

I purchased this amp new in September of 2002. This is a class A two input channel amp (More) for just amazing crunch to high gain lead, and (Less) for pristine clean. However this is not a channel switching amp. This amp is extremley versatile for finding great tones and lots of them with the tube swaping feature plus the cut switch, noise reduction, power output, and hotplate features. I have found numerous fantastic tones using all. It does come with an effects loop which works very well though I do not use it and a line out/instrument feature on the back of the amp. I am using this feature for my wet cab setup going to a GT-6 effects processor then into a Mesa 50/50 power amp into a stereo 2X12. This is used in conjuction with the THD speaker output to another 2x12 cabinet for a nice Dry signal which sounds exceptional by itself. I love this amp so much that I want another just so I can A/B between both the Pristine clean and Lead inputs. I use this amp for live work and recording and has more then enough power to run by itself in any live application.

I am playing a Godin LXGT, and Fender American Deluxe Fat Strat. I mostly play rock which is of 70's style genere. As far as tones, it is hard to beat. You can custom tailor (your) tone very easily just by using the features of the amp plus switching tubes which by the way is self biasing and a very easy to do. I am currently using two Amperx 6550's for the power output section and a 5751 in the input section and a AT7 for a drive tube. Just Amazing sounding. The stock set up is also great but more apt for overdriven tones. I mostly play clean with chorus and reverb to cruch and Plexi when needed. I again would love to have two amps just to punch between those two tones. I have been mainly using the (Less) section of the amp wide open for the prestine full clean tone. If you play mostly crunch to plexi lead you will love this amp. Run the amp in the More input at 3:00 to 4:00 and use your volume nob for switching. This amp does this perfectly. The hot plate feature is great for controling the output volume for practice without sacrificing tone.

This amp is built like a Rock though not too heavy and extremly attractive with both the cover on or off for that vintage look. As far as servicing just carry a couple of spare tubes and plug in if needed.

The support from this company is outstanding I have contacted both prior to sale and after sale and was able to get answers to my questions immediatly.

I have been playing for over 20 years and have owned Fender, Ampeg, Legend, and Mesa Boogie. All which were good in their own way. However I really love this amp over them all. I wish it could channel switch, but that isn't much of a big deal I am just going to get another one to do that. To have an amp of this quality and features would cost as much as two amps anyway.

THD's reputation for quality is number 1! Andy Marshall is on the forefront of amp design. The hotplate and hi/lo voltage selector are 2 more reasons I went for this head. I've always used a hotplate and variac with my Marshalls and have always been very satisfied with the tone created.

Loaded with Electro Harmonix EL34EH's, EH 12AX7 input and a JAN GE 12AX7 driver I really felt I had found the holy grail! I mainly play early Strats and more recent Les Pauls. The tone is just incredible considering it is not a Marshall. Currently I am running it through a Marshall 1960AX cab. A true plexi sound. The power tube compression on 10 is very warm and smooth with an almost harmonic sound. This head really nails what I've been after without spending 4 or 5 grand!

I agree with a prior post recommending spare tubes and fuses if you are going to gig on 10 and hi power for extended periods of time. The construction is rock solid. I can't forsee any problems based on prior experience with THD products.

The support people are very into what they do. They reply to any questions in no time at all. I have dealt with them in the past for questions with my hotplates and heads. I've never had a THD product fail.

Always been a Marshall player. I currently have a '69 50W and a '74 50W MKII. I have an 8 and 16 ohm hotplate,a sparco variac, a TS808 and a KLON.That's it except for delay and reverb pedals. I've been playing on and off for 20+ years. What do I love about this head? TONE,TONE,TONE! I am amazed at the early Marshall tone I can get. Or You can create your own tone with the many tube variations. If stolen I would buy another hands down.

Accepts a wide variety of pre- and power amp tubes. Power tubes can be mismatched (different brands, or even different types, ie 6L6 and EL 34) or you can use only one of the two sockets! The front panel starts with two inputs: "Less" (lower gain) and "More" (you can't A/B between these...when you plug into "Less," "More" is disabled. Next is a High cut switch, volume, treble, bass, attitude (varies the driver tube's effect on output tubes...this is a sort of midrange and texture control...very cool), noise reduction, hotplate attenuator, hotplate on/off, hi/lo voltage to output tubes, standby, power. Back panel includes AC in, fuses with indicators, fx loop, line/inst level out, level control for line/inst out, output impedance selector (two positions: 2/4 ohm and 8/16 ohm), parallel speaker outs. It should also be mentioned that the output has a "dummy" load so you can operate the amp with no speaker connected (ie for running the line/inst level for silent recording or for slaving into a power amp or the front end of a bigger guitar amp).

This is the ultimate club amp--once you get a feel for how to alter it with different tube combinations, it becomes a chameleon that is perfectly matched to every room and situation.

I traded a Univalve for the BiValve. While I really loved my Univalve, it was never enough power...even for rehearsals. However, there's a sonic difference between the two as well. To my ears, the Uni is spongier and brighter. I could coax both "British" and "American" sounds out of it, but I felt it leaned more toward the latter. The BiValve, TO ME, really leans more toward the British side, although it can certainly be made more American.

I mainly use the "Less" channel, as I play funk and R&B. I use an NOS Philips 12AT7 in the input and an Ei gold 12AX7 in the driver. I have generally settled into three basic power tube combinations: 1) Hi power, using two 6550s. 2) Mid power (this is used about 90% of the time), Svetlana 6L6 and an EH EL34. 3) Low power: Two Visseaux 6V6's are great for rehearsals...sometimes I replace one with an EL84 (requires Univalve Yellowjacket adaptor). The "Less" channel has a fantastic clean tone/texture, even at full volume. Cranked, you can get the clarity of clean and unbelievable sustain...

Beyond tube choice, the trick to this amp for me is balancing the volume control with the hotplate (if it's needed) and reducing bass at higher volume settings to keep low end tight. Very quickly , I've learned to do this in an instant...it's easy once you understand the way the controls interact...8 months' experience with the Univalve came in handy here!

It works great with both Gibson/humbucker type guitars and Fender/single coil types. My Strats are HSS, so I'm certainly not an authority (on anything, but especially not on) bridge position single coils.

Although I gig with this in the "less" channel, I love to crank the "more" channel at home. I love to blast out AC/DC, Van Halen, and other very Marshall-esque tones....this amp delivers them in spades! Although I often don't get into a full on tube change, a 12DW7 in the input and a 12AU7 in the driver seem to be the trick for this higher gain channel. I guess it stands to reason that the "more" channel is more susceptible to microphonic tubes...the set I have in the amp now is dead quiet in "less," but unbearably microphonic in "more."

Bottom line: With the right sets of tubes and a good overdrive pedal, you can get just about any sound you can imagine. It's THAT good. Buy one, you won't be sorry!

I had the Univalve for 8 months, and traded it on this about a month ago...Both look and feel solid...I have no reason to expect anything but great dependability.

By email or telephone, THD's customer service is TOP NOTCH! Not only are they personable and quick to return customers' calls, but they are very knowledgeable. I am so impressed that I have effectively become an unpaid sales rep (I'm pressuring my local dealer to pick up the line). Furthermore, when it came time to replace a transformer in my JTM45 reissue, I chose THD over other more authentic repro trannies, because I figure their way of doing business needs to be rewarded...I plan to buy a 2-12 cab and a hotplate (for my other amps) as well...

I've had no problems with my BiValve, nor did I ever have any with the Uni.

In 30 years of playing, the only amp I had that rivaled this in tone was an original '60s plexi (that would be WAY to loud for what I do now). In terms of flexibility, I've seen nothing that compares. I could easily sell everything else...There are only a very few situations where this might not be enough power (outside, big stage?), but you also have the ability to slave this into a power amp! If lost or stolen, I'd be crushed until I bought another...

Straight ahead Class A tube amplifier.Since I was reviewing this product at a Namm show in Nashville, I couldn't get as much time inhand as I would have liked. Best feature over other Class A amps at the show was versatility at the Power output tube stage. Just carry a hotplate mitt and switch on the fly. Super sound at low volume levels and the harmonics were glissening. No onboard reverb that I saw. Too dry at low attack levels.

Best sounding amp in it's class. Clean distortion to play jazz or minor scale/chording. Fat and smooth.

I am looking for one in my area today. I want a used one for under 1k.

This amp is the real deal. Plenty of kick for gigs. It's a dual channel Class A amp (although you cannot switch channels with a footswitch). It has a series FX loop. Volume, Bass, Treble, Attitude (thickens overall sound), and High Cut switch, plus a built in Hotplate that acts like a Master Volume control. There is also a noise reduction circuit that works very well, but does slightly effect the sound.
Of course the main feature of this amp is that you can put different tubes in the preamp, driver, and power tube section, and even use two different model power tubes at the same time, as well as a single power tube for lower volume levels. There is a hi/lo switch that allows the use of tubes that cannot handle high plate voltages.
One other thing, there is a line/instrument out. You can use it for direct recording, to slave a second amp, or even to use the BiValve as a preamp in a larger rig.

Well, at first, it sounded very good. This was with the stock tubes. A Russian EL34 and 6L6 for power, an EH 12AX7 for the preamp, and an El Yugo 12AX7 in the driver. I was not satisfied with very good, so I started swapping tubes. I have settled into two Russian KT88 tubes for power, a JAN GE 12AX7 for preamp, and a Sylvania 12AU7 for the driver. I keep it on the lo voltage setting.
I found that the biggest difference was with the 12AU7 in the driver, which is a very low gain tube. Although it renders the low gain channel basically useless, the high gain channel now SMOKES! It also totally cleans up with the guitar volume knob. I also noticed that the lower gain driver tube made the FX loop more useable for delay, which can get overly compressed when it comes before heavy power tube gain.
I found this amp to be very virsitile as far as styles. You can go from pristine clean, to just breaking up blues, to chunky rock, to searing lead guitar. It's just a matter of matching the tube combination to your particular style. The stock tube setup will cover all these bases, but tube experimentation can allow you to really zero in on the exact tone you're looking for.
The cabinet and speaker is also a big factor. I used both the THD 2x12 w/ classic leads, and an openback 1x12 with a vintage 30. TOTALLY different sounds. The tube compliment I mentioned before worked great with the 2x12, but was way to bright for the V30. Replacing a phillips 12AT7 for the preamp, and putting JAN Phillips 6V6s in the power amp really warmed the 1x12 V30 up.

I went ahead and opened the amp up. The internal design is just amazing. All components are top notch, and the soldering job is near perfect. If you have a habit of really cooking tubes in hi voltage mode, I would bring some spare tubes and fuses to a gig.

This is where THD really shines. I've emailed Ed quite a few times with questions about the amp (the first run didn't include a manual). He got back to me within 24 hours, and many times within only a few hours. They will bend over backwards to accomidate. They really take pride in there work.

This amp is not cheap, but it may well be the last one you every buy. There are many good boutique amps out there, but with most, you're pretty much stuck with the tone they offer. The BiValve allows you to really find your own tone through use of different tubes.
I love the amp. I'd be real pissed if it were stolen. I'd buy a replacement in a second. In fact I may buy a second one anyway.

The Bi-valve has all the features of the Uni-Valve, with the addition of a second power tube socket (The amp came with a 6L6 and a El34, which can be used simultaniously). It adds an effect loop, a high cut switch, the line out is now balanced TRS, it has an additional speaker out, and LEDs to indicate a bad fuse or tube for each socket.

I bought this amp without even hearing it, as I am the owner of a Uni-Valve. My expectations were exceeded. The ability to mix two different tubes opens up many new tone posibilities.
I play modern rock, with a "vintage" edge to it. More of a 60's-70's vibe then the distortion you hear alot today. I am using G&L guitars with Fralin single coils. I go from guitar to a wah, to overdrive pedal into the amp and 2x12 cab, then out the instrument level output of the amp into a analog chorus and delay, and into a Fender Deluxe reverb. I have a dry and wet mic'd cabinet, and let the soundman mix to taste. The line/instrument out sounds very good in this configuration. Where most line outs sound thin due to impedence mismatching, this output sounds great. For true line level use, switch to "line".

I will not rate this, as only time can attest to this catagory, and this amp just came out. I can say, these amps, as anything else from THD, are built like bricks. Aside from the tubes, you could drop it off a moving truck, and still make the gig. I have been touring lightly with the Uni-Valve with no problems.

I've e-mailed with questions several times and always received a prompt and helpful answer. They seem to be one of those rare companies who are very concerned with customer satisfaction.

I've been playing more than half my life, and have been in constant search for the "ultimate" tone. I went from a transistor combo, to a marshall stack, to a full on rack system, to a vintage fender combo, and have finally, aquiring the uni-valve, ended my search. The bi-valve sounds just as good, if not better, and adds some needed features. When I first got this amp, I couldn't stop playing it. For several weeks, I played 4-5 hours a day. It's just that good. You don't want to eat. You don't want to sleep. You just want to be attached to this amp.