Getting Rid of Transformer Hum

Sorry if that confused you. The irony is that transformers hate to have DC provided to them on the inlet but they do a great job of eliminating DC on the outlet side. Then, it usually gets rectified anyway.

That's why I didn't suggest using an isolation transformer in front of the amp. Although it would probably solve the noise in the amp by eliminating DC to it, the iso tranny would be just as likely to hum. The problem might just be relocated. And I like iso trannys.

Should also mention that the reason you don't see a lot of the Channel Islands type of thing and why the DaBlok is DIY is because capacitors aren't intended for AC mains and there is a slight chance of the caps going "poof" or "bang". No, we're not talking dynomite here but it's scary enough for manufacturers. Thus, the heavy duty case, expensive components and the cost.

Have you gone to your breaker panel yet and turned off everything except the wall outlets to the stereo? Unpugged the TV cable and any dimmers or 2 or 3-way lights? You might find the source of the DC is something that seems completely unrelated.

Tvad is right, there are other causes for noise besides DC but I'm stickin' to my story unless you prove me wrong. Maybe even after that.

Here's a post from Roger A. Modjeski on AudioCircle.

"One thing to keep in mind about toroids. If there is any DC on your power line the transformer will audibly buzz and the magnetizing current will go up. This is because they have no air gap. EI transformers have an unintentional air gap of about .001 inches. That's all it takes to keep a transformer happy with a volt or two on the line."

This is exactly in line with my own experience: toroidals all hum/buzz to a certain extent; amps (e.g. most tube amps) that use different styles of transformer tend not to...

I have a pair of Aragon 1Ks and one night I turned them on to hear a loud humming buzz comming from both units. I have a pair of dedicated 20 amp power lines running from the main household fusebox (one to each amp) so nothing else is on those circuits. Then I remembered my home theatre subwoofer making a similar humm/buzz when the halogen lamp in that room was set to half power - on the same cicuit as the subwoofer. So today I went across the house into the home theatre area and sure enough that same halogen light was turned on at half power, so I turned it off and the humm/buzz in my amplifiers dissappeared. Hence, even though it was across the house on a different circuit that light was still feeding DC voltage back through the main fusebox and into the dedicated lines going to my amplifiers. Hope this post helps others.

tone222,

Thanks ! 8 years later and your post solved my AMP5 Hum, a new  halogen desk light set at 1/2 on another circuit.

Salute !