[mgalusha]

It's possible there is some DC on the line. Of course it's supposed to be AC but sometimes there is DC as well and it can make transformers hum and it sounds like the transformer is what is humming. My monos never make a sound but I have them plugged into a BPT balanced power unit which eliminates any chance of DC. However, they never hummed straight out of the wall either. My stereo stratos was always quiet as well.

As others have suggested, call Klaus. He will take care of you.

mike g.

[firestic]

DC? that's new to me. How does that happen?

I'm sure Klaus is a man of his word and if there is a genuine issue it will be handled. But I will give the amp more time first.

The power going to the end of the house the systems is on is a separate run with only a few circuits (3 or 4) it was an addition years ago.

I'm going to look into the power conditioning /regulating ideas for now.

Thanks for all the ideas so far. I can only hope it (hum) does not return and this thread can be history.

Time to crank up some tunes

[mgalusha]

firestic,

Here is some info on transformer hum. Of course PS Audio is trying to sell product but there is still some good info here: http://www.psaudio.com/articles/hum.asp

From what I have read, DC can be introduced into the line by other devices such as refrigerators, microwaves, flourescent lights and other things. Also a post from Jon Marsh on the HTGuide forum (a very smart engineer) mentions "many systems due to unequal load sharing on the distribution transformer phases have small net DC offset on neutral line"

HTH, mike g

[MaxCast]

I do have an excel file on how to find the problem relatively quickly but I dont know how to post it.

If you save it to your gallery you can post the image to any post.  Perhaps here and the beginners circle as a new post for future reference.