Torroid Transformer Hum

Thanks Ian,

Is it worth trying a different unrelated amp? If it still does it suggests wiring otherwise of not maybe the electronics you are using or how it is interfacing with your house?

DC on the mains is really an AC datum offset with distortion, in which you would have more volts on one cycle and fewer on the opposite cycle. I think the article I directed you to has an illustration of the resulting waveform, and to display it safely on your 'scope would require an isolating transformer, or simply take it from your torriodal with some resistance "padding", ensuring it is within the range your 'scope can do.

The "DC mains filters" found online may not have sufficient "diode latitude" to correct it. The diodes protect the big electrolytics against excess ripple which would burn them out.

Maybe the capacitor values don't need to be so large? Much will depend on the VA rating of your transformer. 10uF would give -3dB into a 160VA loaded transformer, so 100uF should work, BUT that would need to be a film capacitor to be able to avoid the use of diodes. The problem here is that such a device if it exists, would cost a small fortune.

Personally speaking, I would use several mains rated polyester capacitors in parallel to make up a suitable value and give it a try, but I cannot advise anybody to do the same because of the dangers involved (that's my disclaimer).