[Arny Krueger]

wrote in message
oups.com...

Ron Capik wrote:

Ah but don't let your brain rest too much yet. ;-)

of course not!

Non harmonic distortion can be created by microphonics
in a vacuum tube. Forces can be created by the signal
that cause the elements of the tube to move and thus
create modulation effects linked to mechanical resonances
in the tube ...not a likely effect for solid state devices.

Actually, there are two effects

(1) Modulation distortion in the form of modulation of an audio signal being
amplified at the same time.

(2) Noise caused by modulation of the bias voltages present in the tube.

Can you provide any measured data about the magnitude of such
modulation distortion?

IME (1) is pretty small, and (2) is quite a bit larger.

Don't assume I doubt you, I have heard the term microphonics with tubes
and while I didn't know its definition, I can understand the principals
you describe. I am curious though as to how much they really play a
part (assuming of course the tubes are *physically* isolated from
external mechanical forces like the rumbling of the speakers).

Hmmm... that being said, I wonder if microphonics are more commonly
caused from air coupling of the speaker outputs shaking the tubes
(similar to a feedback equation with delay),

Or mechanical vibration propigated through furniture and room structure.

and how much is due to internal system issues in-time with the signal
being amplified?

Now we're back to the more common form of distortion due to the nonlinearity
of the tube.