A question about microphonic tubes

[IvanMike]

It was very much like--have you ever pressed 'play' on your stereo and wondered why the music was so quiet, only to realize there were headphones plugged in, and you were hearing them on your desk or floor? Sounded exactly like that, such that I went around and made sure all headphones and speakers in the room were unplugged.

yeah - interesting. Sounds like one of the elements in the tube ended up vibrating, which vibrated the glass, and the combination of the resonant properties of each (and the interactions making the element vibrate in the first place) gave you a little wee frequency band - (the brain fills in a lot of missing details). I noticed that in the professional Electrostatic transducers they don't actually provide all of the sound, and conventional drivers are used (presumably for lows and mids after a certain point).

 

[T-Bird]

Hi.

It was in fact during a bench test, with a dummy load, that I heard it. The reason I asked "is it possible" was to help rule out insanity, indigestion, or other reasons I might hear something so unusual.

It was very much like--have you ever pressed 'play' on your stereo and wondered why the music was so quiet, only to realize there were headphones plugged in, and you were hearing them on your desk or floor? Sounded exactly like that, such that I went around and made sure all headphones and speakers in the room were unplugged.

In that case I'd vote for the dummy load or the OT acting as a transducer before the tubes. Back in the day when I used heater plate from a stove as a dummy load, it sometimes "sang" quite loudly . Tubes usually resonate on a pretty narrow freq range, less than an octave and above 2K or so.

I noticed that in the professional Electrostatic transducers they don't actually provide all of the sound, and conventional drivers are used (presumably for lows and mids after a certain point).

Electrostatics will deliver all the bass one would need listening a natural recorded music. At least mine did back in the day I still had 'em .

Regards
Sam

 

[B-string]

The "singing" could be from the control or screen gid sagging. They vibrate under the infuence of the electrons acting on them, the path would be through the seperators or plate to seperator then to glass(the inverse is what a microphonic tube is).
The transmitting tubes were making sound from about 2KHz up.