[Arny Krueger]

"Ron Capik" wrote in message
...
wrote:

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.

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

Sorry, that's way out of my realm of expertise. Most of my experience
with microphonic tubes goes back to my high school days as a TV
repair person. I have heard tubes "sing" and thus extrapolated
that observation. As tubes age they can become vibration sensitive
and forces in the tubes can make the sensitized tubes "sing."

Microphonic tubes are most apparent in low level circuits with flat
frequency response. RIAA phono preamps would qualify except for the fact
that they are integral with low pass filtering. Microphonic tubes were more
common in PA system mic preamps.