Help me solve another speaker hum thread :)

@noromance to clarify, the speaker still hums when ONLY the MC901 is powered and connected to speaker via speaker cables. No other cables or devices are connected, powered, or even plugged into an outlet. Nothing else is on the circuit.

I checked cable routing, nothing is touching. I tried 2 other dedicated outlets, no effect. I reseated tubes, no effect. I even swapped all tubes with the other MC901, no effect. I swapped power cords, no effect. I disconnected and reconnected speaker cables, no effect. Did not try swapping speaker cables with other speaker, maybe will try tomorrow.

At this point I think there is something wrong with the amp. It weighs 180 lbs though, too heavy to move by myself to the other speaker to see if the issue will replicate.

Guess I’ll contact my dealer.

Just to be clear, this is definitely an issue that needs to be corrected (i.e. a serious issue?)? Or will my dealer shrug and think I’m being a "picky customer"? I don’t know how big of a dealer speaker hum caused by amp is. 

And should I have my dealer address both amps? Even the one that has a barely audible hum with my ear less than an inch away? Or just the louder one that I can hear hum from 6 inches away? Thoughts?

Thanks all

The only time I ever got a hum out of my system (horns and McIntosh tube amps) is when one of my interconnect cables went loose at the plug. Just the slightest adjustment on the cable at the plug at the amp and the hum would appear or disappear. It was still under warranty so I returned it for repair. Now it’s back in my system and no more hum.

Those amplifiers shouldn’t be making any hum or hiss at all. It’s possible the amps are picking up interference from your electrical system. Have you removed the speaker cable from the amps and then powered on the amps to see if it still makes the hum? If they do it is your electrical feed or the amps themselves. 

Ok interesting, sounds like an amp issue. One thing is the electrical buzz you hear when you put your ear to the amp is normal for McIntosh. They all have a bit of buzz in the box (no idea what it is).

Hopefully you get it sorted. Those are complicate amps and it only take one little thing to go wrong. 

Are you sure the small tubes are in the correct positions in both amps? What about swapping them to see if the noise follows them? You could try one at a time. Do you have any WiFi routers or APs nearby?

Ya I’m sure the tubes are correct. I tried swapping all the tubes out with the other amp but that did not effect anything. No wifi or AP’s. I do live about 0.2 miles from 3 AM radio towers and 1 FM radio tower... could that be causing issues? I wouldn’t think so?