Microphonic capacitors!

[Axtman]

I have never encountered microphonic capacitors......now I have two!

I recently worked on a Peavey Mark IV Bass amp that had a terrible feedback howl and a Fender Bassman Ten with a squeal when cranked. They both turned out to be microphonic capacitors. I understand how that can happen since a condenser microphone and piezo pickup is similiar. It was an easy fix once I tracked down what that problem was. Never underestimate the power of the chopstick test!

[Gnobuddy]

I have never encountered microphonic capacitors......now I have two!

I have encountered a few microphonic ceramic capacitors, but that was decades ago, and only in cassette player playback preamps. Those have such gain (full signal level from the tape head is only around 1 mV!) that tapping on any ceramic caps near the input would produce a loud "bong!" in the speakers.

-Gnobuddy

[Justin Thomas]

I've had this in a few amps... 75% of the time it's ceramic disc caps. Sometimes they just make the "bonk," but there have been a few occasions where they ring out and then they have to go. I usually find them when I think a tube is microphonic, but no tube ever changes it.

Of course, so.e tubes are worse than others; I've had a couple EF86s that made the entire chassis seem microphonic!

Justin

[1ampman]

I've had a few of ceramic's & some electro's. Amazing how sensitive they can get.....