Marantz AV7701

I'm using the 8801 with W4S and Bel Canto power amps.

I don't encounter a hum.

One of the main causes of the hum is the ground loop problem. Do you have a cable box attached to it? If you do, try disconnecting the cable box (power/HDMI/coax from cable etc) and see if the hum persists.

If it is still there, try unplugging all other inputs on the AVR to see if you can isolate the problematic source.

+1 on what DH said. Likely some other offending player such as a cable or satellite box. You can even try just the coax cable first as that's often the most likely source.

Tsulzbacher, I had same issue with my 7701. In fact, I went through three brand new units and calling tech support as well talking to my retailer. The tech support was not helpful, and said basically they had no idea. I replaced the 7701 with the 8801 and no hum, call support and asked them why, they responded with, the 8801 is a better unit. I never got a clear cut answer, but the 8801 worked fine, and tried the Yamaha CXA5000, and no issues, so stuck with that. My buddy has the 7701 mated with a Marantz amp, no issues. I'm thinking its compatibility issue with the 7701. My amp is a Mac MC205.