Brothers, I have an issue with my Papus Signature 2061x.
Lately it goes into insane high-pitched microphonic squealing, but only when the guitar's volume knob gets above 8 or 9.
It's evident throughout the preamp gain range, but becomes worse and more easily triggered at higher gain settings.
This occurs on multiple different guitars, but seems worse with single coils.
Master volume level has no effect on the squeal, it occurs regardless of whether the MV is at 1 or 10.
This is NOT microphonic guitar pickups. It occurs with multple guitars, all of which do not exibit microphonic pickups except at insane volume and gain levels - and even then it's more like a low-mid howling sound, not high-pitched squealing.
I'd say the squealing frequency is around 8-12kHz.
Now I know a lot of people will immediately say "microphonic valves", but I don't understand the relationship to the guitar's volume knob.
Anyone care to explain the science behind this, thanks.