THD Bi-Valve Head

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.