How to get rid of transformer hum?

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.

Tommy, I apoligize for my over simplified explaination but have you thought of something like the PS audio box that recreates or regenerates the sine wave? Another possibility is a used ac power source. I have seen some manufactured by Elgar at some of the used test equipment houses for about $1.5K to $2K. Good luck.