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Getting Rid of Transformer Hum

I just picked up a Proceed AMP5 the other day. Upon hooking it up to a power cord, I noticed an annoying pulsating hum that sounds like a lightsaber match in Star Wars. This hum is coming straight from the amp, not the speakers, so it's not ground loop. There is nothing hooked up to the amp besides the power cable. What's interesting is that the amp is even though there is a standby mode, the amp was definitely turned off!

I noticed, though, that the hum got louder as the voltage from my wall dropped below 115-ish. Lowest it got to was 109 when everything was turned on, including a halogen lamp. Well, I turned off the lamp and all the lights in the house, and unplugged them -- helped the voltage drop but didn't eliminate the hum.

Am I completely lost on this amp? Or is there a way to take care of this problem without investing thousands more on some power regenerator? Another poster mentioned a similar problem solved by tightening a "chassis ground screw", but I have no idea what/where that is.

Help!
rakuennow
rwwear
2,867 posts
 
An amp will hum without interconnects hooked up and speakers and power attached. Does it hum with the interconnects attached? If so, is it hum or vibration? If it is hum it may be fixable if vibration, probably not, unless the transformer has become loose. If the transformer is loose, you may be able to tighten it.

But I had a Krell amp that had a noisy transformer years ago and Krell had to send me a new amp.
Post removed 
david12
1,454 posts
 
I had a loud hum from what was a well designed amp, with a toroid reansformer, a Karan K180. As I understand it Toroids are prone to hum and it is mechanical, at least in part. I found an Audience AU 24 power cord cured it immediately, a bit to my suprise
jswarncke
66 posts
 
I had this problem with my Spectron Musician ii and subwoofer amplifier, and it did end up being a result of DC in the line. As far as a I know, the only company selling a solution right now is Channel Islands Audio. It is a two outlet box called the XDC-2, $299. It solved my problems completely. Call them and tell them what you have, and they can recommend the proper configuration.
ngjockey
1,042 posts
 
Core saturatuation caused by DC. Period.

Question is whether it's coming from inside the house or outside.

The irony is that transformers are great at eliminating DC.

http://diyparadise.com/dablok.html
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