How to get rid of transformer hum?

Tommy, have you tried to power these amps at another local? Away from your home? I saw that the mfg stated that its a power problem. I may not be an EE, but I have over 20 years in the field and 9 times out of 10 its not the equipment or the power but another source of noise on the line saturating the transformer causing it to hum. I know we all hate the power company and sometimes they are at fault. I'm just curious as to whether the problem follows the amps when they are powered somewhere else.

Here is the diode thing with a filter.
http://www.hifi-notes.com/ahacoffsetkiller1-en.htm

Mrderrick

The amps were at another home with the same power company. They didn't hum there. I listened to the my parasound amps in my surround system and they hum too, they are behind a wall and the transformers are about 10% of the size of the Pass. I've had the power company out and I saw the sine wave on there scope it was chopped off at the top. Just not enough for them to work on fixing it.

While it may not be a feasible solution for some, try moving. The transformer in my DAC hummed audibly (hearable from ~2 feet away) and it was almost on its way to the factory for repair. There was also a seemingly unrelated hum through the speakers that floating the preamp's ground removed, though the overall sound was better with the ground enabled.

Well, I moved last week. Bigger and much more modern place. Especially the wiring. Previous place was a unit in a '50's era fourplex; new one is a "condo" (though NO shared walls) that's about ten years old.

When initially set up in the condo the DAC still hummed and the pre-problem was actually more pronounced. A couple of days later the DAC hum is completely gone and the speaker hum caused by the pre- is only audible from a scant few inches away.

Can't explain it, but what a relief!

Fpeel, this is a different problem than yours. This does not sound like a ground problem but it sounds like the culprit is power line harmonics. The chopped off top of the sine wave suggests that something looking similar to a squarewave is feeding the device. A squarewave's spectral makeup is the sum of all of the odd harmonics. If you looked at the power line on a spectrum analyzer you would probably see lots of odd harmonics. I believe it is these harmonics that are making the transformer laminations loosen and vibrate.