Faint, "buzzing" guitar output noise coming directly from the amp itself (possible Red Box issue??)

My apologies in advance if this topic has already been covered. If it has and someone could point me to the right thread, I'd appreciate it.

I could have sworn I'd read something about the issue I'm experiencing before, but maybe it was on another forum. I've noticed that my GM40D is emitting actual guitar noise through... *something* even when the speaker and/or studio monitors are turned off. This only seems to happen with gain above 12 o'clock on the Lead and Ultra channels. I'm quite certain that what I'm hearing is a somewhat faint, very buzzy rendition of my guitar's processed output because it follows the notes and articulation of whatever I play.

Basically to reproduce the issue, I put the amp in silent mode or simply put the Red Box output into my audio interface, then turn down the monitors or put my head close to the amp while picking a few notes. Please note that even though I say I put my head close to the amp, I am not getting any microphonics from any of the tubes. No squeal or hum; this is definitely a very scratchy sound of the actual guitar!

Again, I could have sworn this was covered somewhere and that it did have something to do with Red Box, but I can't find the thread or remember whether there was any resolution. Maybe it was just a dream. Will update this thread if I'm able to figure anything out on my own.

Hi there.
Maybe it was not just a dream,
one thing in this thread sounds similiar:
https://handkusers.forumotion.com/t503-sound-coming-out-of-the-head-high-gain-squeal?highlight=sound

Ah, that must be it! Thanks very much. Not sure how I missed it this time.
I'll have to try running my Grandmeister through a load box but still into the audio interface and see if the sound still comes through. If it does, I'll necrobump that post just to keep it all in one place.

Thanks again!

This could be down to simple microphony in some components.  If a valve say is microphonic which all valves are to a lesser degree, parts of it are capable of slight movement in response to physical vibrations.  This generates slight changes in the distancing of parts inside which in turn changes the electrical characteristics and can be heard in the signal through the component.  The same is generally true in reverse, electrical changes through the component then can produce sound vibration.  Transformers are another component where this generally happens.  Most mains transformers hum or buzz to some extent in response to the changing mains current through them.  It doesn't surprise me that some amps will emit sound in response to hard playing.  Of course it is usually drowned out by the sound from the speakers and at any level it should be very faint. Even the load box itself could do this as could the components in the internal power soak.