is it present when the motor spins or stopped?
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Here are 2 images:
1. A picture of the board (the right side of the picture is the phono stage)
2. A drawing of the board.
After viewing the drawing, do you still think that there are caps related to DC regulation that might only affect the high amplification needed for MC cartridge ?
With MM cartridge I have no hum problem.
I thought about it and I don't think it's a problem with the caps in the phonostage DC regulator due to 2 reasons :
1. I replaced them 3 years ago.
2. If this was a regulation issue related to caps, the hum would be present all the time. In my case it is present only when the TT is plugged in.
This means that it comes from the TT. Most likely a grounding issue but since I measured continuity between the bare metal of the arm to the amp ground I don't know what causes the hum...
More valuable info that might support the claim that the hum comes from the TT:
When I disconnect the small connectors of the cartridge, the hum is gone.
I verified continuity of all 4 wires:
1. Red to + right
2. Green to - right
3. White to + left
4. Blue to - left
All are ~ 1 ohm.
Why is the cartridge producing this hum then ?