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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

HELP!!!!

:-(
gsxr
restock
831 posts
 
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!

Rene
jameswei
883 posts
 
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.
hammertone_audio
16 posts
 
Try disconnecting your cable input to your TV . If that's the culprit , your local cable guy can install a reducer .

Best of luck
joefama
60 posts
 
When did the Hum/Buzz first start ? What piece of equipment did you hear it first?
adasilva
57 posts
 
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.
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