In article , Dave Plowman (News)
scribeth thus
Had a bit more of a play. Disconneced the cartridge - hum goes. So it's
apparently being induced into the cartridge itself, rather than wiring. No
large transformers anywhere near - and it's more or less the same on the
workbench, in a different room. Next thing to try is removing the mains to
the turntable, I suppose.


Dave.. seriously suggest a small value resistor connected across the
inputs and that via a short bit of twin screened and see if the hum is
still there or not.

Then connect the cart to the same cable and move that around it
shouldn't under normal conditions "hum" unless its picking that up from
a transformer or motor. If so then you should be able to track that
easily.

In a way this is much the same as a moving coil microphone and they can
and do as I'm sure you know be used on rather long leads....
--
Tony Sayer