Audio Research Refernce 75se

I had one in my system. Awesome Amp should have kept it. No noise at all. I would pass

Just the clarify .. the noises are coming through the amp, not from the speakers.

Unplug all the inputs and see if it still hums.  If not, you might be hearing a humming phono input or cables that are picking up electromagnetic noise.

Sure sounds like a transformer buzzing☹️. Bummer, I would pass. But that model is such a tremendous amp… I really recommend finding another. That is the kind of product that can change your audio life and  every purchase in the future… in a good way.

if you hit the back of it hard with a rubber mallet sometimes the noise will go away

try not to hit the glass tubes