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KM56 power supply and Screws
Old 5 days ago
Here for the gear

KM56 power supply and Screws

I replaced the tube in a KM56 and had a question about supply voltages. The schematic shows a B+ voltage of 120vdc. The power supplies that are being used with the mic have a max output of around 80vdc. I was told that these are Dan Alexander supplies but I have not been able to confirm it.

I am assuming the low voltage is responsible for the low output. I want to verify that the B+ needs to be around 120v. I was hoping someone could tell me the typical plate voltage on the KM56.

There seems to be some sort of regulator (possibly a zener diode) dropping the rectified voltage of around 200v to the 80v level. I cannot identify this part and I have so far been unable to locate a schematic for a Dan Alexander supply to verify.

Also, one of the capsule screws and the two body screws are missing. Is it possible to find replacements?


PS - yes, the heater voltage is set to 4 volts at the tube
Old 4 days ago
Lives for gear
Klaus's Avatar

Contact Dan Alexander or James Gangwer ([email protected]) who did most of Dan's technical work in the (distant) past, to verify it's one of theirs.

I doubt that the B+ of Dan's power supply for a KM56 would have been artificially lowered to a voltage where the mic is barely working or not at all. You [u]must[/] feed 120VDC ± 2VDC to the mic in order for it to work properly.

If the power supply is too low quality, and cannot be improved, contact Scott Hampton in Portland to make you a decent one.

Housing screws for your KM56 ("Madenschraube") can be ordered in two colors from Neumann/Sennheiser.

Last edited by Klaus; 4 days ago at 04:03 AM..
Old 1 day ago
Here to make the endorsement: we've got some of Scott Hampton's PSUs for our KM56s and 54s; he's/they're great.
Old 12 hours ago
Here for the gear

Thanks for your reply, I'll reach out to them to see if I can get schematics. I don't believe the supplies were altered, I just think the regulation device is failing.

I realized I could probably contact Neuman just after I posted but thanks for the info. I'll contact them for replacements.

And thanks for the endorsement, I will pass the info on to the owner.
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