THD Bi-Valve Head

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.