UniValve Lit 7/15/01 - THD Electronics

1 UniValveAmplifier Introducing the THD UniValve Amplifier!The new THD UniValve is a Single-EndedClass A amplifier head with a single output tubethat can be switched at will among many octal-based power tubes for different tones withoutre-biasing the amp. Useable tubes include 6L6,EL34, 6550, KT90, KT88, KT77 and the amp in LoV setting you can use 6V6for a total output of 5 watts. A special UniValveYellow Jacket Converter is available allowingthe UniValve to use the popular EL84 powertube at a total of 4 watts output power, also in LoV , the two preamp tubes can be anycombination of 12AX7, 12AT7, 12AU7, 12AY7or UniValve delivers tones from smooth andclear to very aggressive overdrive.

2 It is easilycapable of driving a 4 x 12 cabinet, yet is quitesmall and light. It has a built-in Hot Plate Power Attenuator that allows for full outputdistortion at almost any volume. And it doesn tcost as much as you might is Class A?Class A is a term given to an amp that runs itstubes at full current all the time, unlike mosttube amps that alternate between running oneset of tubes and the other set, each for one half of the wave. The set not in use is turned offby a positive swing of the grid voltage. Single-ended output stages always operate in Class push-pull amplifiers, including the venerated Vox AC-30, operate in Class AB whenoverdriven, even if they are in Class A while clean.

3 Class A operation has its own unique tonalcharacteristics that set it apart from other tube amp A amps sound great at low volumes, and even better as you turn them up. Thus, withthe relatively low wattage of the UniValve you can turn up the amplifier to take full advantageof its stunning output distortion tone without deaf-ening single-ended, the UniValve has a much fullerharmonic content to its overdrive and distortionbecause it is rich in both even and odd push-pull configuration that most amplifiers usecancels even harmonics leaving only half of the sonicspectrum offered by the the self-biasing feature?The UniValve s circuitry senses the current needs ofthe output tube and provides the correct bias voltageto the cathode of the output tube regardless of tubetype or wear.

4 Without any trip to an amp technician,you can simply replace the output tube with one thathas different sound characteristics. (Of course, youcan also change the preamp tubes at will for evenmore tonal variations.) For example, a 6550 will staycleaner at higher volumes, but when overdriven, hasan astoundingly woody character to the the other hand, an EL34 will break up earlier than Please turn 6550 and give a more British sound. The ever-popular 6L6 familyof tubes gives a tight overdrive with less power than a 6550 but moredetail than an EL34. Even within the same type of output tube thereare harder and softer tubes. Two guitarists playing with the sameguitar through the same UniValve , who simply switch the tubes totheir preference, can have noticeably different and FeaturesThe UniValve has two inputs: one for high gain and one for low gainranges.

5 The low gain input with 12AX7 preamp tubes in the amp givesa wide range of clean sounds from Country clean and crisp to Jazz-direction warmth. With the controls pegged and a relatively high-output humbucker, the low-gain input can deliver a very convincing Texas Blues type of overdrive. Plug into the high-gain input and youare in a whole different world from early British Invasion tones tocontemporary hard rock sounds. The most surprising aspect to theUniValve s high-gain overdrive is that even with stunning levels ofgrind, you can still play complex chords and hear every note of thechord clearly. There is none of the mush and confusion normallyassociated with high-gain controls are the traditional Volume, Treble and Bass controlsalong with what we call an Attitude control.

6 The Attitude controldetermines how the driver stage responds to the signal and how itdrives the power tube. The Attitude control is not a Presence control,as the amplifier has no negative feedback from the output transformerback into the driver stage. There is also a built-in THD Hot Platepower attenuator that lets you have full output distortion at anyvolume level. The Hot Plate has its own hard-bypass switch on thefront panel, which completely removes it from the circuit for Full-Power playing into a UniValve features a light bulb on the front panel that not onlyglows when the amplifier is played, but it also provides very effectivenoise-reduction. For occasions when you do not want this feature,there is an On-Off switch for the light bulb circuit right on the UniValve now has a HiV/LoV switch, which reduces the voltageto the tubes somewhat like a Variac.

7 In the LoV setting, the power isreduced more or less to half, pick attack is slowed and the feel is moreTHD Electronics , 15th Avenue NWSeattle, WA 98107-4717 USAP hone: Fax: elastic . The amp also has more bloom in the LoV setting and canalso take a number of tubes that cannot withstand the higher voltagesof the HiV setting. These tubes include the entire 6V6 family and anumber of antique 6L6 family tubes like the 6L6G, 6L6GA UniValve has a GREAT- sounding transformer-isolated line out on the back panel complete with anadjustable level control and a switch to choose Line-or Instrument-Level signal. The transformer used inthe line out was chosen for its pickup-like impedanceand tonal characteristics.

8 Most amplifiers line outsonly work well when used to drive other poweramplifiers, and sound harsh and thin when pluggedinto the guitar input of an amplifier. Not so with theTHD UniValve . Even into the input of a Marshall100-watt head, the UniValve provides a warm, fat,tight and sweet sound that FEELS like an amplifier,not like a preamp-amp rig. The UniValve can driveany speaker load from 2 all the way up to 16 .When there is no speaker plugged into the speakerjack, the amp uses its own built-in dummy load so nodamage will occur, and to allow the silent use of theamp for direct recording purposes when miking acabinet is not UniValve will initially be sold only as a head. Itfeatures a metal chassis, powder coated and enclosedin a perforated steel cage to protect the tubes.

9 In thecoming months, we will be introducing a number ofdifferent combo cabinet and head box configurations. The UniValvecan be installed in any of them simply by screwing it into the will be a huge range of choices and options in the cabinetsincluding head boxes, 1-12 combos, 2-12 combos, 2-10 combos andothers. We will periodically produce Limited Edition cabinets withspecial hardwoods or other unique features. Anyone with a UniValvewill be able to use these as swapping cabinets only takes about fiveminutes!(Oh, and it looks pretty good, too.)So, go to your nearest THD dealer and try the new THD UniValveamplifier. You will be glad you did.