Buzz/hum from amps, NOT from speakers

I have been tearing my hair out over over a buzzing noise coming from almost every component in my system. I have it in all three subwoofers, the power amp, preamp, and - the latest addition - my new HP plasma TV. All will "buzz" quietly as soon as they are plugged in.

Using a power console makes no difference, and I've tried both a Monster Power 3500 MK2 as well as a Belkin PureAV PF-60 (both are ~$500 units). I've tried the ground-plug "lifters" that turn a 3-prong AC plug into a 2-prong, same problem, no change. Removing the audio interconnects makes ZERO difference. The noise is present with ONLY the AC cords attached. I tried shutting off EVERY breaker in the panel box except the one that feeds my system, no change. I have tried different circuits, no change.

Sunfire mentions this in the owner's manual, which sounds like what I'm dealing with, but they offer no solution:

"If the hum is heard from within the
TGIV and not through the speakers,
this may also be caused by
interference on the AC or DC lines.
The power transformers may turn
this interference into an audible
noise. Internal hum can be made
worse by a shelf or cabinet resonating,
so try moving the TGIV to another shelf."

Equipment affected:
Sunfire TG IV preamp
Sunfire Signature power amp
Sunfire Signature subwoofer
Polk SRT main powered subs (L&R)
HP PL5060N plasma TV


Is this the first equipment you've used at this location??? If not, did your old stuff buzz too? If no old stuff, maybe buy a $29.95 boombox and see if it hums. And then call an electrician would be my take on it.
You mean the equipment itself is physically buzzing/vibrating? Sounds to me like you're getting lousy power from the utility company -- probably low power (well under under 120 V, like 100V) and maybe off-cycle. Check your power at the wall outlet using a simple volt-ohm meter. You may wind up needing a power regenerator like an Exactpower EP-15A (conditioners won't do anything to fix this problem).
Most likely you have a strong 120 Hz noise riding on your lines. One hint: I had a similar problem on one of my amps: The problem was caused by a dimmer that caused the transformers to buzz at 120 Hz.

A good way to diagnose the offender: Shut off all lines in your place at the switching panel and leave only the line to your system running. If the hum disappears keep adding line by line and see which one and if possible which appliance on that line causes the problem. If it doesn't disappear I would talk to the your electricity supplier.

Good luck!

You've got really noisy power. It's so bad, there's likely a problem in the outside line. The power company should fix it. Suggest you contact them.
Try disconnecting your cable input to your TV . If that's the culprit , your local cable guy can install a reducer .

Best of luck
When did the Hum/Buzz first start ? What piece of equipment did you hear it first?
Sunfire Manual Says -> "Internal hum can be made
worse by a shelf or cabinet resonating"

This is exactly the problem I had with my CJ amp. I could hear it across the room and using a cheater plug made very little difference.

The noise was actually due to a mechanical resonance in the amp case. I was able to queit the amp by loosening the middle screws on the cover and leaving just the corner screws tight (don't know if this is possible on your amp). This changed the machanical resonance of the amp case and resolved the vibration and hence the noise. This was recommend by another Agon member on a thread (since removed) about amp hums.

Eliminating the machanical resonances also reduces the electronic distortion that can be heard through the speakers. I can now use may amp without a cheater plug which of course is best.
I'm up in the Seattle area. After the wind storm and major power outages, I have buzzing in all my components, mainly the amp. I actually watched the line crew change out the toasted transformer on the pole. They ran new lines for an 1/8 of a mile. Voltage at the house has been 117 to 118. Some days it jumps up to 125v. I did have everything unplugged during the storm so I know it's not storm damamge to the equipment. I would probably contact the power company and let them know almost all your appliances are buzzing.
I have the same thing. Sometimes the buzz in all components get somewhat loud, then it slopes down to be totally quite. It then starts the swoop again and gets louder to then go quite again. Sometimes the buzz comes on and stays on when components are on.

Anyone deal with that? That must be a power issue????
Hi everyone, thanks for the replies! Here's an update, and some answers to your questions:

Nsgarch: I agree, I believe it's dirty power. A voltage check shows 119-122VAC, so it's not due to low voltage. I'm hoping to avoid buying a regenerator, as those are very expensive, and if they need to handle high current (power amps), they're even more expensive. And I have multiple amps! :-( Thanks for the tip on the Exactpower, btw. I hadn't seen that unit before.

Tarsando: No, the old equipment buzzed too, but each item has the problem to a different degree. Some are worse than others. Bad news is, I used to be an electrician, lol... I've already checked for the obvious stuff. ;-)

Restock: I already tried what you describe - shutting off all circuits except the one feeding the system. Same problem. I too was hoping it was something in the house causing it, which I could replace or remove. I may need to contact the power company. :-(

Jameswei: I agree. See above comment.

Dbtrucks: I don't have cable TV, just a DVD video source. No coax of any kind connected to the system. (yeah, I'm weird, lol...)

Joefama: First noticed it with the Polk SRT powered sub amps. They were the first item it was loud enough to hear from across a quiet room. When I upgraded from Adcom to Sunfire pre/pro, it got worse, probably due to the larger internal transformers in the Sunfire stuff. The latest is the plasma which I just bought last month (although that mostly buzzes when turned on.)

Adasilva: In my case, the cheater plug made zero difference. I'm hoping to find a better solution than physically opening up the equipment and damping the offending component (see update below).

Freemand: See update below.

UPDATE: I found a product by PS Audio that claims to cure this exact problem. It's not cheap, however. And the original product is no longer manufactured or sold. The new, replacement product is 2/3 more expensive ($499 vs the original $299, MSRP). Click links below for details. I couldn't locate the old product anywhere, but I found a place that sells the new one for about 25% off list price. I ordered one, it will arrive today, I should know if it works by tomorrow. I'll post my findings here. If this unit doesn't fix it, I will definitely call the power company next. A regeneration unit is the last resort due to the excessive cost ($1-3k).

PS Audio Humbuster (was $299, but no longer available):

PS Audio UPC-200HB with Humbuster circuitry ($499 MSRP):

PS Audio Premier power regenerator ($2195 MSRP):
Bad news: The UPC-200HB didn't cure the problem. I think it may have reduced it, but not $400 worth. I sent an email to the power company already.

Anyone want to buy a new-in-box UPC-200HB? Drop me an email...

The power company came out and did some testing, and so far they are stumped too. They're pretty sure it's coming from the line somehow (outside my house) but at the moment we're not sure how to locate the source, or fix it. They're going to have a senior technician come out with fancier test equipment (oscilloscope, RF detector, etc) sometime in the next week or so. Stay tuned...
Did you ever fix your problem? Were you able to determine anything regarding the Belkin Power conditioner's performance beyond not being able to fix your specific problem - i.e. any positive or negative effects on the overall sound of your system? Specifically wondering how it worked with your higher power amplifiers?