In article , Sumatriptan
wrote:


Most are higher order harmonics of 50Hz mains but some change in level
and frequency over periods of seconds and minutes.

Again, that seems like the cartridge and its wiring are acting like a
pickup for EM fields around them.

Is it possible for you to try something like a 10 Ohm resistor in series
with the deck's ground wire to the amp? And if you have a spare headshell,
try that with its wires open and then connected to make shorts?

No idea if that will help, but its the kind of experiment I'd try to get
some more info to think about.



Motor is mains. If this mains supply is disconnected the hum level falls
by about 5 dB

By "disconnected" do you mean 'pull plug from wall socket' or 'using the
switch on the deck'? Do they give different results?

Jim

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