Hey guys,
So I've pretty much finished my AKM78 microphone, but after everything is in place, there's still some annoying little bit of 60Hz hum coming out of the output. Here's the grounding diagram (ground connections in black):
Pin 1 of the output XLR and the ground of both the B+ and heater PSUs go to a single point in the chassis, which in turn is connected to AC mains ground. The case of the Tuchel mic connector is metal, so it's grounded where it touches the chassis, which in turn grounds the shield of the mic cable and the mic body itself.
I can't see anything wrong with my grounding, but please let me know what you think.
There are about 40mVp-p of crap coming out of the business end of the high voltage PSU. Can this be the culprit? Maybe some extra filtering is in order?
Any comments at all are welcome...
Please? :?
Peace,
Al.
So I've pretty much finished my AKM78 microphone, but after everything is in place, there's still some annoying little bit of 60Hz hum coming out of the output. Here's the grounding diagram (ground connections in black):

Pin 1 of the output XLR and the ground of both the B+ and heater PSUs go to a single point in the chassis, which in turn is connected to AC mains ground. The case of the Tuchel mic connector is metal, so it's grounded where it touches the chassis, which in turn grounds the shield of the mic cable and the mic body itself.
I can't see anything wrong with my grounding, but please let me know what you think.
There are about 40mVp-p of crap coming out of the business end of the high voltage PSU. Can this be the culprit? Maybe some extra filtering is in order?
Any comments at all are welcome...
Please? :?
Peace,
Al.