Never heard an amp do this before, ideas?

@ieales 

yes, all volumes levels and on all channels. Covering the unit with a faraday blanket does attenuate the sound.

@mastering92 thanks for the advice, I tested two primaluna amplifiers, both did it. I also tried a cheater plug.

Update: wrapping a faraday blanket over the unit dampens the sound. But the source of the RFI is not from my apartment, because it happens with everything in the apartment unplugged and off.

Does this mean all tube amps will do this and I'll have to go SS? 

@mwinkc it's a (not very safe) bypass on ground, so you can rule out ground loop issues. I think you're right, it's environmental. Unfortunately I don't think it's related to electricity, it's probably radio interference. Because the only thing that made the sound almost go away was wrapping the thing in a faraday blanket.

The disappointing part is that I can't fix that-- it's probably coming from outside. So I'm wondering if SS will be as sensitive to RFI, or if I can get away with hybrid.

@yage unfortunately yes, inputs have no effect. 

@oldaudiophile led lights on dimmers, a WiFi router, hvac, and refrigerator. A few switching power adapters plugged in throughout the apartment. Florescent lights in the bathroom.

All of these things are suspect to me, most are pretty far from the unit. I've shut down breakers and made sure lights/hvac/wifi/refrigerator are off without effect, though.

​​​​​​I'm in an apartment on the 4th floor in NYC. About 8 floors up is some Verizon equipment. Across the street there is a big service elevator.

part of me is thinking I should find a way to locate the RFI noise somehow, but I'm not sure how.

@knock1 I didn't know it's bad, but yes normally I have both speakers attached, I had been moving it around testing and wanted to make a quick video.

@ieales yes, it has a headphone jack and I unattached the speakers, the sound comes through the headphones.

@ieales thanks for the suggestions, I purchased some plugs and I'll try that!

I have svs speaker cables, but it happened with headphones and no cables too.