What causes microphonics ?


I have a Rogue Magnum 99 preamp. Sometimes it exhibits microphonics, and sometimes it doesn't.
I have found this very difficult to eliminate. I have tried numerous amounts and types of different tubes. It still comes and goes. One time I turn it on , and no problems. Next time, it's there.
Also, does this effect the sound ? I would assume it does in some way, but I am not positive.
Thanks, any info would be appreciated.
Scott
scottht

Showing 1 response by clueless

Hi:
generally in my experience it is the tubes and, to a lesser extent, capacitors. Capacitance is the culprit. The voltage across a tube or cap depends on the distance between the elements or plates. If these move because they are loose due to vibrations (either you tap it with a finger or vibrations from the music) the voltage accross the elements/plates must change. Since the audio signal is kind of stored as voltage at this point in the stream you must hear the effects of this change.

Some microphones are designed to work in this manner. They are just special capacitors. When you blow/sing on one sensitive "plate" it moves and the distance between the plates changes and creates/changes the voltage.

Sean: If it is caued by bad solder joints would you consider it microphonics or some other kind of noise?

Cheers
I remain,