Help me solve another speaker hum thread :)


My dealer recently installed a set of Sonus Faber Aida’s with 2x McIntosh MC901 monoblocks. I also have 4x dedicated lines.

The problem is I have have hum in both speakers (hum in the midrange only. The tweeter makes a different noise but I read that’s more normal?) One speaker is louder than the other. Neither changes with volume. The louder one can be heard at about 6 inches away, the quieter one needs my ear as close as possible to faintly hear anything. Sound from both is 50hz maybe 60hz hum. Both monoblocks also make a slight mechanical buzz that can be heard about 6 inches away.

If I have only one speaker, speaker cables, and monoblock powered (nothing else connected, powered, or even plugged in), it still makes the hum.

I have tried using a cheater plug for possible ground loop, also a DC blocker. Neither made any difference. What do you guys think the issue could be? Bad tubes?

Do I need to send the amps back? Or just live with it? I don’t hear from listening position or anything. Thanks in advance.

Ag insider logo xs@2xbattbot

Check the routing and connections of the cables as @oldhvymec  said and then pull and re-seat all the tubes.

 "Sonus Faber Aida’s with 2x McIntosh MC901 monoblocks."

Con$iderable investment there...

Noticeable hum at ANY level except at neurotic audiophool distance(press ear against the speaker) would not be acceptable IMO.

Get your dealer involved, he wouldn't want to see your gear come back.

Try all the simple things as suggested-reseat every possible connection. 

@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.