Tube vs clean amplification

Posted: 11/27/2012 6:29:33 PM

Joined: 11/24/2012

Hello all, first post here but I have been reading from the site for a few weeks now. I am a musician that owns an commercial AV business and I enjoy designing and building amplifiers and unique things. This is where I am coming from.

We all know that an amp/speaker is a part of the instrument too. In building tube guitar amps I am never really looking for distortion levels below .1 or so, so high levels of signal distortion (compared to hifi) make a guitar sound good.

On the other hand there is hifi. All of the commercial audio work I do deals with low distortion amps and speakers - and is certainly more true to the recording.

Reading here, a lot of people use tube guitar amps or keyboard amps.

The Question: What is the tubes effect on the tone? (amp tube, not instrument tube) Is a perfectly clean Theremin tone desirable?

So if anyone is up to the tone lowdown - let me have it.


Posted: 11/27/2012 9:12:08 PM

From: portland

Joined: 11/30/2011

As the theremin has a range of 5-7 octaves it needs an amp that has a wide frequency response. The general consensus (as much as there is one) is a keyboard amp or a small pa system. For melodic, non-experimental playing, in general, a clean tone is desirable  Clipping distortion is, in general, not desired, and in general, most people play with minimal numbers of people, and arent playing that loudly. 

Some people have been known to use tube based eq, and a harmonically rich signal is good. And I think even harmonics, but dont quote me on that.   

To play accurately, and on key, one must clearly hear themselves play, and clearly hear the main note, as there is no tactile feedback, and it is a continuous tone instrument (hence the above) Also, you want the amp ideally, to point at the players ear, so either wedge shaped, like a stage monitor, or raised on a stand. Also, open baffle designs were often used, for their effect on the tone.  

Posted: 11/28/2012 4:55:26 AM

From: Small town Missouri on Rt 66

Joined: 2/27/2011

All of the above is quite true BUT....

Have a look at some of the wave forms HERE and you will see that the "ideal" theremin sound bears a striking resemblance to an over driven, asymmetrically clipped guitar. Bear in mind that those samples were taken from the output terminals of a classic RCA which uses a single ended triode output. They to not take speaker response into account.

This is not meant to detract in any way from what nieradka has pointed out. I just think finding the perfect theremin tone is as personal a thing as finding the perfect guitar tone. A lot also depends on which theremin you play. An EW Pro is going to be a completely different animal compared to my Kustom, or an EW standard, or one with Thierry's module installed, etc.

I do play my solid state theremin through the same amp I use for guitar. A 30 watt all tube channel switching combo of my own design that can be set for reasonably flat response. I also use a modified Fender Deluxe Reverb, and a pathetic little Epiphone for a practice amp because it has a headphone output. The Epi sounds like "fertilizer" through its built in eight inch speaker.

The tube amps are always pointed at me for both guitar and theremin by planting them in a chair and tilting them back, or leaning them against a wall. If I ever need more power, I'll mic them.

My theremin is rather dull sounding through a clean system. It has enough output to soft clip the first stage of my tube amps, and this helps the tone quite a bit. Again, your mileage may vary.

When I get some of the projects that are overwhelming my bench finished, I'll probably build a dedicated tube type theremin amp with a diamond speaker.



Posted: 11/29/2012 12:01:11 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

"The Question: What is the tubes effect on the tone? (amp tube, not instrument tube) Is a perfectly clean Theremin tone desirable?" - Rohbiwan

First, Welcome to TW, Rohbiwan!

Ok, first - When it comes to opinions on what is "desirable" from a theremin tone, well - you will not get a common answer to this question anywhere.. Opinions about the "best" or most "real" or "authentic" tone are as mixed up as the people who play these instruments.. Musicians are generally more mixed-up than the general population, and theremin players (and developers) well - we are all completely mad!  ;-)

So all I can give you is my personal opinion and ideas about theremin tones and tubes.. These opinions are no more valid than anyone elses, and probably less valid than many because I live in an isolated technical bubble, dont really play, and meet a musical person once every few years if I am lucky... LOL  ;-)

The tone from a pure theremin (here I am taking about true analogue distortion-free multiplication for heterodyning), if not processed or distorted internally or externally, is generally sineusoidal and (IMO) boring. Most theremins apply liberal doses of distortion (usually on the audio signal - but in many cases at the mixer, and in some cases by distortion of the HF oscillator waveforms) and IMO it is the care in the selection of distortion mechanisms which determines who the sound will please.

Further distortion can be applied to the audio signal after it has exited the theremin - and one of these possible mechanisms is the amplifier / speaker.

I believe that one thing which adds "warmth" to the tone (gives it an acoustic quality) is microphonics - as in, the sound from the theremin causes mechanical energisation (vibrations, resonances etc) which somehow feed back and/or modify the actual tone produced by the theremin.

I believe that tube microphonics is the primary mechanism which makes tube amplifiers sound "warm" (not just for theremins, but for everything) - and that the soft clipping behaviour of tubes further enhances the sound in some cases.


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