Help me solve another speaker hum thread :)

If you can determine its the amps, yes, send them back

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

Don’t do that.

Put a 10db pad (attenuator) on the preamp to amp cable. 

Have the dealer come back and address the issue.  

I have found this type of hum is often in the power supply. Do you have another amp to try?
 

When my subs are connected between my pre-amp and amp (internal highpass) I get a faint 60hz buzz. I found no work around and will replace the subs at some point. I use a McIntosh MC462 and it has a hair of hiss with my ear by the tweeter and when the subs are in line a 60hz buzz. I have also had my system pick up my Xbox or computers power supply. 

The first thing I would do is make sure the cables are routed correctly. It sounds like cables are plugged, dropped and forgot. 1/2 the time I can fix noise in a system with routing cables at 90 degree crossing and nothing closer than 1/2". Over, under or along side. I’ve done it that way for 45+ years. My systems are OLD and new all have no noise (not low) NO NOISE. You pick the source and turn it all the way up. If you stay still and don’t jump up and down in the room with the TT selected even that is quiet. ALL valves too. C20, ZP3, V12R. Dark background..

I’d look there first.. Tubes be careful what you have close to what.. Power supplies from Laptops and Cable boxes can be noisy too.

220/40 is an option too for the 901s and use the balanced side. What are you using for a Pre and Source?

Regards

Can you try it all on one of your four dedicated lines? 

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. 

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?

I spoke to my dealer today, they are gonna come take a look. I'll update the thread when they do. In the meantime if anyone has any great ideas, feel free to share :)

if its not DC or other power issues coming from your line, dimmers are bad for adding noise on the line, than its probably a tube. Try tapping the tubes when on see if your getting any microphonics out of any of them. Try taping them quite hard to see if there may be some particles trapped in a tubes grid etc.. if you have a second set of tubes try them. 

You seem to have done all the normal things we do to find hum, other than internal issues ie bad component, its most likely tubes or power delivery from your wall. maybe try an different outlet other than your dedicated lines, extension cord may be useful. 

I was getting a hum from my McIntosh MC302 amp and C2500 tube preamp.  It took a lot of snooping but it turned out to be the Apple iPad charger I had temporarily plugged into the Furutech power distribution block.  Once I removed it, hum was totally gone.