Amp transformer buzz/hum from DC on AC line?

I have measured .46 volts DC on the line to both amps.

How did you go about measuring the DC voltage on the AC line.

DC voltage on the line can cause transformer mechanical noise.

http://sound.westhost.com/xfmr.htm#7-noise

http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html

http://www.altavistaaudio.com/hum.html#trafo

Are you sure your amps have the 60HZ transformers used in the US as opposed to the 50Hz transformers? Sometimes if a transformer is designed to see 50Hz putting it on a 60Hz line can cause hum.

I second what Jea48 said. I have deliberately induced hum in transformers with DC as an experiment and solved a number of DC problems with simple DC blocker.

As of the last while, I had a buzzing/humming sound coming from my Plinius 9200 integrated. Fairly loud - I could hear the sound from 5 or 6 m away in my listening room - but didn't seem to affect the sound from the speakers. There was always a very slight buzz from the speaker, but you had to hold your head pretty much up against the speaker with volume at least 3/4 (with no input!) to hear this. I attributed it to normal operation.

During my early period of owning this amp, same thing happened. Conctacted the Plinius rep and had a replacement torroid supplied for replacement; Plinius acknowledging there were issues with an early run of the torroids. Solved the loudness of the torroid, with a minor but still present buzzing persisting. Thinking my recent problem may be a hardware issue again, contacted Plinius. This time, they suspected DC on the AC line. While somewhat suspicious, for no sound reason other than what occurred the first time, I decided to start checking this out.

Long and short, this thread among many, arrived at the suggestion of using the Humbuster III to handle any DC (if any present). Picked up one and it arrived today. Put it in line with the Plinius, sparked the system up, and no noise whatsoever. I had to put my ear against the amp to confirm the status 'on' light. A couple of hours of listening to some familiar material, no veiling or change in the sound of the music. In fact (and I think this is my mind at play) I thought there was a slight increase in detail and ambiance in some of the solo piano recordings that I had been listening to. And I should add that slight hum in the speaker that I attributed to normal operation is no more.

For $200-odd bills, an incredible device.