Here is my new phono stage, made of left overs, ALWSR boards and NA323 cards, and it makes 50Hz hum:
I checked these threads about wiring (especially grounding):
My signal ground goes from the input to the output socket, from there directly to the NA323s, from the NA323s to the star-GND point between the PSU and the ALWSRs where all other GNDs are connected to. PE is connected to chassis (it's an old Mission PSU case). If I disconnect PE from the chassis the hum becomes incredible loud, so I keep it connected. I checked with my scope: I don't see any hum on the power in/out lines at the ALWSRs, only at the output of the NA323 boards I see hum. If I connect PE/chassis to signal-GND the hum improves a lot, but still has about 10mV at the outputs of the NA323s. I don't have a cartridge, so I tried to load the NA323s with 100k in series with the input and 220R across the input: no difference. What can I do?
I checked these threads about wiring (especially grounding):
My signal ground goes from the input to the output socket, from there directly to the NA323s, from the NA323s to the star-GND point between the PSU and the ALWSRs where all other GNDs are connected to. PE is connected to chassis (it's an old Mission PSU case). If I disconnect PE from the chassis the hum becomes incredible loud, so I keep it connected. I checked with my scope: I don't see any hum on the power in/out lines at the ALWSRs, only at the output of the NA323 boards I see hum. If I connect PE/chassis to signal-GND the hum improves a lot, but still has about 10mV at the outputs of the NA323s. I don't have a cartridge, so I tried to load the NA323s with 100k in series with the input and 220R across the input: no difference. What can I do?