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MF MD HG01 Electric Guitar Month 06-19-18

THD Univalve Amp with Groove Tubes

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Product 481284
Product Price $0.00
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The UniValve delivers tones from smooth and clear to warm and full to aggressive overdrive. The single-ended Class A circuit design utilizes the high...Click To Read More About This Product

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Tube-swap your way to a whole new tonal territory.

The UniValve delivers tones from smooth and clear to warm and full to aggressive overdrive. The single-ended Class A circuit design utilizes the highest-quality parts and hand-built construction for clean and faultless operation.

The single output tube can be switched at will with nearly any octal-based power tube for different tones without re-biasing the amp, and the 2 preamp tubes can be switched for any combination of 12AX7, 12AT7, 12AU7, 12AY7, or 12AZ7 tubes.

The UniValve is easily capable of driving a 4x12" cabinet, yet is also small and light. Its built-in Hot Plate Power Attenuator lets you experience the indescribable freedom of wailing away with full output distortion at volume levels that are quiet enough to let your neighbors sleep.

There are 2 inputs”one for high gain and one for low gain. With 12AX7 preamp tubes the low gain input gives a wide range of clean sounds from Nashville clean and crisp to Memphis down and dirty. With the controls pegged and a relatively high-output humbucker, the low-gain input delivers a tantalizing Texas blues overdrive. Plug into the high-gain input for a whole new world”from early British Invasion tones to modern high-gain metal attack”but with none of the mush and confusion normally associated with high-gain tones.

The controls include the traditional Volume, Treble, and Bass along with an Attitude control knob that determines how the driver stage responds to signal and how it drives the power tube. There are also controls for the Hot Plate, including a hard-bypass switch. The noise reduction circuit in the Hot Plate features a light bulb fixture on the front panel that glows when you play. There is an On-Off switch for the light bulb.

On the back panel the UniValve has a transformer-isolated line out with an adjustable level control and a switch to choose line-level or instrument-level signal. The speaker outs on the UniValve can drive any speaker load from 2 ohms all the way up to 16 ohms. When there is no speaker plugged into the speaker jack, the amp uses its own built-in dummy load so no damage will occur, and it's awesome for direct recording.

  • 15W Class A amplifier
  • Single-ended Class A circuit
  • Hand-built
  • Accepts almost any power tubes in any combination
  • Ships with 2 - 12AX7s (preamp) and a single EL34s (power amp)
  • 2 preamp tubes can be any combination of 12AX7, 12AT7, 12AU7, 12AY7, or 12AZ7 tubes
  • 2 inputs: one for high gain and one for low gain
  • Volume, Treble, Bass, and Attitude knobs
  • Built-in Hot Plate output attenuator
  • Volume, Treble, and Bass controls
  • Attitude control knob
  • Hard-bypass switch for Hot Plate
  • Light bulb noise-reduction circuit
  • On-Off switch for light bulb circuit
  • Transformer-isolated line out with adjustable level control
  • Choose Line-Level or Instrument-Level signal
  • 2 ohms to 16 ohms speaker load
  • Built-in dummy load

Review Snapshot

by PowerReviews

(based on 3 reviews)

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Reviewed by 3 customers

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Just what the doctor ordered

By No Greater Joy 4 Keek

from LaPine, Oregon

See all my reviews

Fellow tone seekers, I played this the other day at our local guitar store and was amazed at how many different rich tones it could produce. It also has a well needed attenuator built into it which is of great use because this thing cranks. I ended up buying the handwired Marshall 2061 which was obviously more expensive, but I am still considering adding this one to my collection as well. Check out the Thd bi-valve also. Both are awesome to look at and incredible to play through. You will not be disappointed, so rock on doctor doctor please!!!!!!


Awesome Tube Amp

By Anonymous

from Undisclosed

Running the Univalve through a 2X12 Marshall cab. The versatility of this little amp is great. The Chinese EL34B they send is too creamy for me. Buy a Svetlana 6L6 for the power tube and this thing really comes to life. A little pricy but well worth it.


Why I LOVE the THD UniValve 15 amp

By Les Paul Blues Rocker

from Northeastern Wisconsin

The THD UniValve 15 (15 watts RMS with most tubes except the 6V6 tube, then its more like 10) is definitely a happening amp, at least to me. It has two inputs "Rock" - which is higher gain, and "Roll" which is lower gain. I use the "Rock" input. I use this amp all the time for my practice amp, but with a big enough speaker cabinet or a small enough club it would have enough "juice", unmiked, and you could also send the signal to the PA via the effects send jack on the back for more power. The most useful feature on this amp (to me anyway) is the built-in attenuator. The attenuator can be turned on and off. In Full Power mode, it acts as a noise reduction, and the rotary control knob is non-functional (its "on" in the "Lo Power" mode), and a yellow light will flash depending on the signal strength. This can be used as a kind of "tone control" in the Hi Power mode - some people might like this (I do... sometimes - its similar to a "soft" tube rectifier response). I LOVE the attenuation feature because I can turn everything up to 10, and still be quiet enough not to wake up somebody in the next room. It won't be as cool as cranking it wide open, but if you want to practice without headphones with full-bore overdrive at 3 a.m. without getting a call from the police, you can (use Lo Power mode). The tone is as varied as the combination of tubes available (and speakers), so there are many different tones, but I LOVE the way mine sounds with the 6V6 in full or partial overdrive. I am driving a ceramic Mojotone 12" speaker in an Audiozone cabinet (closed back) at present (for convenience mostly - it fits on my desk!), and using a 6V6 power tube - the ONLY tube that REQUIRES you to use the "Lo Voltage" setting (I didn't spell it wrong - that's the way it reads on the amp - same as the "Lo Power" setting). There are 4 rotary knob controls on the front panel (not counting the "chicken-head" attenutator knob): volume, treble, bass, and "attitude" ("gain") - the more "attitude" the more overdrive. Although this amp is actually quite basic it is a QUALITY piece of gear that is built like a tank - you could probably hit it with a hammer in a lot of places and not hurt it at all, although I DON'T recommend you do this! There is also an effects send jack with a level control on the back, and you can select the ohm rating of your speaker cabinet. This amp is not cheap, but it is worth every penny - in my opinion, all of the THD amps are. I have tried this amp with single coils, P-90s, and humbucking pickups, and if you adjust the tone controls you should get a good sound with all of them, especially '57 Classic humbuckers and Burstbuckers (with the 6V6 power tube). However, with all the different tube combinations you can use on this thing you could experiment for years. This is a PRO piece of gear that with proper care should last a lifetime - or more. For more information, see the THD website. Also, with the "Yellow Jacket" adapters, you can use EL84 tubes (and perhaps others?) as well if having a "boat" load of tube combinations available to you isn't enough! If you don't think this amp will have enough power for you, try the BiValve 30 (which I also own and love and use for gigs that I know might turn into a "volume fest") or the Flexi 50 (which I'd like to own!). Disclosure: I am NOT a THD representative - I just happen to LOVE mine! I have owned a lot of amplifiers, and although this one is quite basic everything on it is excellent - I'm keeping mine because for what I use it for it is great. A giggable amp that I think is also the greatest practice amp in the world. This amp would also "kill" (in the "nice" sense of that word) in a studio recording setting. IMHO, IT ROCKS.

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