Kanfive. Call ATI and tell them what is going on. I suspect you need a new transformer. You can also check the transformer mounts. Some companies isolate the transformer from the chassis with special mounts. Check the hardware. In your case I believe your amp has two transformers.
ATI AT6007 amplifier hum
Long time reader and first time poster. I recently traded in my Pass Labs X600.8 amps to ATI AT6007 and AT528NC combo for my 9.1.4 setup. I have 3 dedicated 20A lines which I’ve used previously for the pass labs and now for the ATIs. I did not hear a hum from the pass labs but I’m now hearing a hum from the AT6007. I’m also using proper 20A power cables. There is no hum from the AT528NC. Please advise. Will I need a DC blocker or power conditioner?