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JayTronics Tru-Tone 2-watt tube amp

User reviews at Harmony Central -- effects area
User reviews at Harmony Central -- amp area

Brendan wrote:

John has just built me a 'Black box' for my studio. the black box is a simple valve stage that can be used as an insert on all sorts of things, it is switchable 1 or 2 stage amplification, has input and output controls and a bypass Switch. The tonal quality is variable from a little warmed up to totally mangled, a very useful studio toy. I haven't tried it as a Guitar DI but it should be pretty good for this job as well, it certainly has enough gain.

John isn't on the Internet yet (but we are working on him!)

-- Brendan Minish

Can be used as:


The processing chain matches the arrangement of the front-panel controls from left to right.

  1. Input jack
  2. Input Boost switch
  3. Bass knob
  4. Mid knob
  5. Treble knob
  6. Eq Level knob and footswitch jack on front
  7. Volume knob
  8. Presence knob
  9. Send jack on back
  10. Return jack on back
  11. Master Volume knob
  12. Output Level knob to control internal speaker, external speaker jack, and headphone jack
  13. Headphone jack on front
  14. External speaker jack on back
  15. Direct Inject jack on back
  16. Line-level Output jack on back
  17. Built-in speaker (2 1/2 watts) in top of case.

Volume-related knobs:

  1. Volume
  2. Master Volume
  3. Output Level

[to do - scan and upload .jpg's]

Historical Background

Designer John Truba replied to my letter, including the following:

This has been a long time coming, but now at last there seems to be a great interest shown in my valve-based designs.

I find that people are interested in knowing the how, why, when, and where of my amplifiers, especially the younger guitarists. It sems to me these days with the re-emergence of valve gear and the music of the 50s, 60s, and 70s, they all want to know about your roots in the vintage-amp era.

The Jaytronics Tru-Tone system was developed after a long history of my involvement with guitar-oriented electonics, beginning with my very first 1 1/2 watt valve amp (previously a bakelite-cased intercom system with an 8" speaker). I used this for a few gigs as a rhythm guitarists in a Shadows-based band. Next came an amp (which I bought for 1 pound) with a 12" speaker and a pair of KT33C's as the output valves producing the best 10 watts anyone heard (great for the early Rolling Stones numbers). However, unknown to me at the time, this was a lethal device (AC/DC operation, with no mains transformer to provide a degree of safety). Yes, you guessed it -- at one gig, early on, I caught the full whack of 235 volts mains across my hands and chest! I soon learned to insert the mains plug for correct polarization (where there were still 2-pole operation circuits here). This happened in 1964 and I'm still here today with no ill effects (I think!).

This amp sowed the seeds of valve technolgy firmly into my system. I was a 60s kid (luckily), attending college once a week, serving a 5-year apprenticeship (also known as slave labor) working in an audio company learning about valves, transistors, and related circuitry. In my spare time at home I built gear using all sorts of designs from books and magazines, and also repaired various domestic items such as radios and televisions.

In 1966 I began to build small amps between 1/2 watt and 1 watt -- all-transistor types with self-contained speakers for friends to practice at home, without blasting the family members into oblivion. I also built a miniature replica of a Marshall 8x10 stack -- a loud 3-watt amp, batteries housed in the speaker cabinet together with its 6x4 speaker setup.

By this time, I had owned (for a year or so) a Burns Orbit 3 solid-state combo amp with 3x10" speakers, producing 60 watts. This was not my choice of amp, but my mother's, by virtue of the fact that she was able to get it at a discount from 120 pounds down to 100 pounds at her place of work -- Harrods. I wasn't complaining; it was loud and had reasonable tone, filtering, and a reverb. In other words it turned on and didn't try to electrocute me. I also had an early WEM Valve Copicat. But even with this higher-power gear, including home-made distortion pedal/booster units, the sound wasn't as good as my 1-watt solid-state amp or earlier "Lethal" 10-watt valve amp.

In the following years I owned all sorts of heads, stacks, and combos during stints with semi-pro and pro bands, but I always preferred low-power units, which would easily produce overdriven power-stage sounds -- generally valve amps. Even in the studio in 1970/71, my little 1-watter did the business in the booth while in the next booth was a non-master-volume Marshall trying to achieve a good sound. At that time there were very few amps with master volume; mainly this feature was mainly found in P.A. amps.

Due to professional and semi-pro activities as a guitarist and to various jobs in the following years, it took until nearly 25 years later to put into motion a multi-purpose low-power valve amp; I built the prototype in 1995.

A lot of thought went into the design of the Tru-Tone amp system. I reject the common approach many manufacturers take of employing only double-triode valves. My system employs full Class A amplification scaled down to 2 to 3 watts R.M.S. maximum.

The system's requirements spec was to meet the needs of pro guitarists and amateur home recordists as well as practice amp requirements. Therefore, the unit serves in multiple applications, including as a low-level recording amp, a practice amp, and a rackmountable preamp for stage use feeding high-wattage power amps and speakers.

I see this unit almost like a gig-bag accessory as opposed to being permanently installed in a rack case. The musician would have it at home or in the hotel room, then having practiced, put it into the bag on the way to the gig, use it for backstage tune-up, then rack it into the onstage equipment ready for the gig.

I am flexible with regard to customers' suggestions or modifications.

-- John Truba, February 1999


John Truba
JayTee Services
The Olde Schoolhouse
Conor Pass Rd.
Co. Kerry, Eire

Someone wrote:
>The adress and the phone number were what i needed to get in touch with John Truba.  He gave me the following second phone number ...

I was originally told by someone else the following, which doesn't necessarily match the information John Truba mailed me.

"John Truba is an Ex-WEM engineer who builds 1/2 watt [?] all-tube rackmount guitar amps which are switchable from Class A to A/B from the front panel. They come with Direct Out jacks, an effects loop, and other features. They have a small speaker built into the lid and have an output jack so that you can drive an external cabinet. 2-space rackmount casing. All outputs are available from the back and front panels."

My Original Letter Requesting Information

Dear Mr. Truba,

Please send information about your low-wattage tube amplifier.

The guitar industry has been too slow to learn that for very quiet cranked-tube-amp tone such as at home, power must be reduced by factors of 10, not by half. Magazines review 20 watt amps, calling them "low power" and asserting that they are appropriate for home studios and apartment recording studios. But 20 watts is practically as loud as 50 watts, and even 5 watts is still in the same range; 5 watts is as loud as a trumpet and remains far, far too loud for most apartments and for many houses. But the entire industry has been slow to learn and accept this. People *think* that the quiet level they want is achieved by a 5-watt tube amp; but what they really need, for that level, is a 1-watt, 1/2 watt, or 10mW tube amp. I have been spreading awareness fairly effectively, through my web site and the newsgroups and email to designers and editors, that we need a discontinuous, radical jump, down several orders of magnitude in power, to reach the goal of personal, private, headphone-level cranked-tube-amp tone, without the neighbors or housemates being able to hear that an electric guitar is being played.

There are just a few tube power amps that are truly low-power, though there is a tremendous demand or wish for private, quiet cranked-tube-amp tone.

One reason that radically low-power tube amps are required for the home studio, as opposed to the pro studio, is that the home studio is really no studio at all; there is no acoustic isolation between a control room and performance room, therefore, it's impossible to clearly hear the monitor speakers or headphones when the guitar speaker is blasting away at 5-50 watt levels. Mic positioning, mixer tone controls, and other post-amp processing thus can only be adjusted effectively during playback of a recording -- when the guitar speaker is not in use. Thus, for recording or monitoring a post-processed signal at home, the guitarist emphatically does *not* want to hear the guitar speaker directly.

Many beginning guitarists, who are unaware of recording and post-processing considerations, are satisfied with the idea of playing a guitar amp fairly loudly; they think that that is an appropriate listening level and a reasonable, necessary fact of life that they have to accept. But for recording and post-processing, a blasting 5-watt tube amp is impractical, almost impossible to monitor accurately, and also simply unnecessary: the world used to be filled with 1/2 watt and 1 watt tube amps, in radios.

Guitarists are too accepting of the status quo, even though it's a looming problem that they complain about: the amp only sounds good when it is played at a level that generates complaints from neighbors and housemates. Yet the guitarists are not demanding low power amps -- they just don't think in terms of exerting pressure to change what products are available; they have a certain helpless attitude when it comes to available tube amp power ratings. The solutions they try for the volume problem are everything except the most obvious and straightforward. They try attenuators, DI units, amp simulators, and so on, and none of these produce an authentic cranked-tube-amp tone, but what's really needed is simply lower-wattage tube power amps. So I have been encouraging guitarists to ask for truly low-power tube amps. When guitarists start asking for such products, the industry will provide them in suitable quantity, with a variety of packaging approaches (micro-compact combos, head-and-cabinet, rackmount, pedal, floor processor, and so on).

My site has information about products and projects which are similar to yours. The Studio amp by London Power (Kevin O'Connor) uses Power Scaling for 0-10 watts output, and much of the testing during product development was done at the milliwatt level. The Lexicon Signature 284 has 3 watts for the left channel and 3 for the right, and can drive guitar speakers directly *or* use a built-in dummy load and cabinet simulation filter. The Lawbreaker pedal is a 4-watt amp that supports those same two options -- though 4 watts is too loud for home use, in many cases. The Cream Machine and the Moonlight Amp project both use a preamp tube as a 1-watt power tube; the Cream Machine can drive an internal dummy load and cabinet simulation filter, or drive a guitar speaker. The Guytron, Warwick ProTube IV, and ProTube IX are heads that have an EL84 driving an internal load followed by a final, high-power amp; the EL84 is used purely as a tone-generator/processor, rather than for audible amplification. The AX84 is a collective project, now complete, to build a 3-watt tube amp, with a custom, traditional metal casing available, and full design specs to assist modifications and teach tube amp design. These and related products are covered in some detail at my web site, along with resources such as some 20 tube amp design books.

I would especially like to see a 1/2 watt tube amp treated as a signal processing module and incorporated into various packaging approaches such as modelling amps, multifx units, software processing systems, heads, floor processors, and pedal chains. My solution to the "tube amp or modelling amp" debate is to combine the two; integrate a 1/2 tube amp in the middle of a multifx processor *before* the time-based effects. The processing chain would then be the same as the chain that is actually the standard used in pro studios when you look at the *entire*, actual, processing path all the way from the guitars output jack to the mixing board's output jacks:

EQ-based effects (wah, phaser, pre-dist. EQ)
Preamp distortion
Tube power amp
Guitar speaker(s) and mic(s) (and support internal dummy load and cab.sim.filter as an additional alternative)
Post-amp EQ (like tone controls of mixer)
Time-based effects (post-amp, for amp tone clarity) (like fx loop of mixer)
Post-amp compression (like tape saturation and FM broadcast preparation)

Using conventional multifx processors, this processing chain can be implemented with the following product chain:

Multifx processor 1
Low-power tube amp, speaker, mic (or amp, load, filter)
Multifx processor 2

A few of the best processors, such as the Rocktron Prophecy, can handle both pre-amp and post-amp processing, with full, ideal processing order; the post-amp time-fx placement is achieved via customizable fx-loop placement.

Your 1/2 watt [?] amp could provide the breakthrough example and demonstration that what guitarists really need, to fulfill their goal of quiet cranked-tube-amp tone, is a milliwatt-range tube power amp, rather than 5 watts, and that such a small amp could be thought of as another processing module, rather than a public monitoring amplifier, and combined with other processors, to achieve what the current [preamp] tube multifx units and modelling amps and can only claim: a harmonious, musical combination of authoritative, actual, non-simulated cranked-tube-amp tone, quietly, with complete tonal and effects processing.

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