High Frequency Static in single channel - MA352 & MA352

Yup, hum moves from Left to Right if I move the speaker cable, the noise always stems from the right AMP terminal (have tried different cables as well).

Amp doesn't have a crossover so that's not it, speakers aren't it either because the hum follows from side to side and goes quiet from the left terminal/regardless of speaker.

This is also the second amplifier we've tried, both brand new and tried swapping tubes, no luck.

My only guess left is environmental, I'm in an older, slightly busy NYC building and just wondering if I'm in a crazy weird spot picking up someones devices or wifi or who knows.

If the problem happens with nothing physically attached to the inputs, and you’ve tried swapping tubes I’d say you have an amplifier problem and should have it serviced. 

It is possible that for some reason you have one channel slightly more susceptible to RF than the other channel, and it’s a design issue. 

Despite my suspicions it is worth attempting to identify if you have a particularly troublesome source of noise in your home.  You can help identify EMI/RFI sources by turning off every other circuit except your amplifier.  Also turn off any lights which are left on, and unplug network devices still powered on after shutting down the rest of your home. 

I’ve heard of all sort of crazy things, from Wifi routers, LED light strips and home automation devices being the causes of interference so that’s why the breaker method is nearly fool-proof unless you forget to turn off lights and or have a wall wart plugged in and energized somewhere ont he same circuit. 

Yeah that was my first inclination, but this is the 2ND brand new Macintosh amplifier and found out this is now their most popular product so fairly certain it's not a design flaw.

I have disconnected all things plugged in and tested, and still persists. I'm wondering if maybe my room and the combination of the Tube preamp (built-in) is picking up something.

Well, I've laid out a couple of things to try.  If you have another building you can try the amp in that can help too. 

Ground look hum occurs when ground and signal path share same wire. Guessing your computer is not on a 3 wire ground. I would suggest adding a wire from the chassis screw of the PC, to a known ground (center screw on wall outlet, or use a 3 wire prong plug, attach ground wire to ground pin, and plug it in