Hi!
I have the same or a similar problem.
I bought two MTMs from Thomann in 2019. They were perfect, but about two weeks ago, I connected an old guitar effects decive (POD XT) to my computer (via USB) and connected the speakers to them...when turning on the POD XT, I got a bluescreen of death, Windows crashed and my speakers had a very loud beeping noise.
After turning everything off and rebooting my computer, I noticed a low-level noise in both speakers.
I am not 100% sure, BUT I think the MTMs were completely silent until this bluescreen of death, and the noise problem only resulted from it.
I ordered new speakers from Thomann, connected them...and they both had the same low-level noise.
Now I don't know if
a) my old speakers were completely silent until my accident, got damaged and the new ones have the low-level noise problem described in this thread
b) my mind played a trick on me and the low-level noise is normal.
I tried old speakers, new power cables, new speakers, new cables, even a different audio interface...but the problem persisted.
The speakers are connected via good XLR cables. Is it possible that such cables get damaged when there is a bluescreen of death because of a potential feedback loop of my computer and the POD XT? It is either broken cables or new faulty speakers or my mind plays tricks on me.
Here is the noise recorded with my phone. The low-level noise and me pressing the power button to turn them off:
https://www.seelenpuls.at/temp/rauschen.mp3How should MTMs be when connected to the computer? Completely silent or with a low-level noise?
The number (model number, production date or whatever) of my old speakers from 2019 starts with 190558...
My new speakers start with 221005...
Please help!