Microphonic stages-the high gain stages like for TT preamps,mic preamp,tape heads where you need high gain the microphonics are more of a problem.For high level and low gain stages-not an issue.Some solid state devices can be microphonic,too-Varicap diodes in some FM transmitter exciters-these had to be mounted in a foam insulated drawer and temp controlled so it won't drift in frequency.And in solid state high gain stages-carbon resistors in them can react like carbon microphones making the stage microphonic.So film resistors are used instead.And of course in something like a hi-fi console where the amps and speakers,TT in same cabinet microphonics can be a big problem.Turntables have to be well suspended and insulated-and not mounted above a speaker.Folks are so startled when I show them the microphonic SS stages--esp that FM exciter-you tap it--and you get a loud "SpronnnnGGGG" from the receiver or monitor speaker-and if the transmitter is on air-will be heard over any radio receiving that station.With newer FM exciters and transmitters this is no longer a problem.And some AM tranmsitter oscillator stage tubes can be a problem-since this is a low level stage in the transmitter-if you tap the tube while the transmtter is on-you will get overload trips from the higher power stages.This even happens at where I work-the low level modulator stage preamp tubes 5879--tap or bump these while on air and you get multiple modulator overloads.I have seen so many 5879 tubes it isn't funny in broadcast gear-favorite tube in older Gates consoles for mic and TT preamps.Line amps in these use them,too.And of course these show up in hi-fi stuff,as well.
Oh yes,with those older SS FM exciters they had to be mounted in a separate rack from the transmitter RF power amps-the blowers in these will raise havoc!!!
