What causes a pedal enclosure and footswitch to become microphonic?

[bluelagoon]

Have built another FA-1 preamp, pretty basic same as Boss FA-1, only with a mid range control and a Baxandall out select switch option.
This is the first time noticed anything like this . When the bypass foot switch is engaged its all very silent with the actual switching using a relay and some momentary mute circuit function to keep it quite. however all the mechanical noise of the switch is coming through to the amp as being picked up microphonically somehow . Also, tapping on the enclosure has same microphonic affect.
Usually means a capacitor is picking up the noise somewhere in the circuit, is what I believe is usually the case with microphonics, just need to narrow down which cap it is, very strange, and unusual phenomena indeed.

[bluelagoon]

Well did some digging, the noisiest cap when tapped was the 10nf input cap, So changed that out, made no difference. Then noticed it was prevalent from tapping the input jack end of a 10 foot Fender lead. So swapped for a shorter lead, and straight away, there was no microphonics. Cant say have noticed it previously, may have just always put it down to switch noise. Looks like now I am up for a new upgrade guitar lead. Problem Solved, I hope.

Most likely was the TRIBOELECTRIC EFFECT -

https://www.shootoutguitarcables.com/guitar-cables-explained/microphonics-triboelectic-effect.html#:~:text=Not%20all%20extraneous%20noise%20from,triboelectric%20effect%20of%20electrical%20charging.

https://www.pedalsnake.com/blog/2016/08/dealing-cable-microphonics/

[PRR]

I know the $10 word but I think most cases are simpler. I've had a LOT of bad solder and bad crimps make sound when shook.

[bluelagoon]

Is this like a game of Wordle, where we have to guess the $10 word, with only 6 goes at it?
Its a mystery to me, what could the $10 word be?
Are there prizes?

[FiveseveN]

I think he was referring to triboelectricity.
I was going to suggest an imperfect connection as well, applies both to the pedal and the cable.

[bluelagoon]

I figured that may be the $10 magic word. Its definitely new to my vocabulary.
 
Have myself a new MXR 10 feet lead now, and it works a treat, no more microphonics.

[mozz]

Ceramic caps?

[antonis]

Ceramic caps?

For $10 ..??

[Dormammu]

the noisiest cap when tapped was the 10nf input cap, So changed that out, made no difference.

Ceramic or other solid cap can be quite microphonic. Need to install a film one.

[PRR]

new to my vocabulary

Moreover: while the concept may be older than Christ, the word "triboelectric(ity)" hardly appeared in print before 1910, and didn't become common until 1984.

[Paul Marossy]

[splitting hairs]

Have not heard of the term "TRIBOELECTRIC EFFECT" but I am familiar with the other term commonly used to describe it.

I wouldn't use the term "microphonic" to describe that sort of noise. In my experience, static electricity causes crackling and popping noises. Where I have experienced that is with Strats which have a single ply plastic pickguard. I use anchored hand technique and my fingers rubbing on the pickguard generated static electricity, which in turn would be heard as small popping noises when I touched the strings. It was very annoying! A 3-ply plastic pickguard almost completely eliminates that.

I do have an effect or two that have so much gain that it will pick up the sounds from your pickup switch, or tapping on the bridge. I have one wah pedal that will pick up the noise from you tapping on the enclosure. Those are examples of what I would microphonic.

[/splitting hairs]