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[Paulmaroon]

New poster here! Klaus recommended I come here. So quick question...who would you guys recommend to fix a pair of Schoeps 221s with a slight low end hum? Hopefully in the US.

Also, I have a Telefunken badge 221 that is working well...can I plug the Schoeps mics into that power supply to see if its the mics or the power supply? I have a feeling its the power supply because I have two of the Schoeps (it's a stereo supply) and they both have the same slight hum.

Please let me know and nice to meet you guys!

Best Paul

[klaus]

I am not familiar with any M221 dual-supplies (assuming they are Schoeps-branded), but if they generate completely separate supply voltages, i.e. if you don't all of a sudden have a heater supply boost beyond 4.1VDC, try plugging in just one of the two mics, mate it with one of the cables, into one of the two supply channels.

Altogether you have 3 variables twice- supply x2, cable x2, mic x2. To isolate the culprit, you need to combine in your testing all combinations so that all options of connecting them together are covered.

f none of the possible connecting possibilities reproduce the hum, then it's a cable termination issue which sometimes occurs when two mics are connected to the same supply ground.

[afterlifestudios]

So your Tele-badged 221 has its own working supply too?  If so, (and its voltages are correct) plugging your Schoeps 221 into that supply would seem to be a good trouble shooting step in my eye.

[David Satz]

Klaus, you could state your impression more firmly if you like, since it's 100% correct; Schoeps never manufactured any two-microphone power supplies for the M 221 series, or any other of their tube microphones for that matter. Telefunken sold Schoeps' model N 20 (single-channel) supplies, with the Telefunken designation Ela M 931, though the M 221 could also be used with any other supplies properly made for AC 701-based microphones.

And hello, Paul--welcome. I hope that the hum problem can be solved without much trouble. Unfortunately Schoeps no longer repairs this series of microphones. But servicing the amplifier is generally a simpler task than doing work on their capsules, especially the multi-pattern ones.

Just for general background information, there were three distinct series of "M 221" microphones: the original from 1954, the M 221 A / M 155 from 1955, and the more widely sold M 221 B from 1960. A version was also made for French broadcasting, sometimes called "M 221 F". Finally, a very small batch of a dozen or so M 221 B amplifiers was made up years later from spare parts that Schoeps still had in stock. Each series had its own range of capsule types which were interchangeable on the amplifiers of only that series. (The M 221 F had the capsule fittings and polarization scheme of the original M 221; its capsules won't fit on an M 221 B, and wouldn't perform properly even if you modified them to fit (written in error; see following two messages).) All versions had identical power supply requirements, however.

--Please note also that a company in Hungary manufactured a large number of counterfeit M 221 B amplifiers during the 1960s, many of which are still circulating on the used market. They were made with inferior tubes, output transformers and other components, and have higher noise and distortion than the genuine article.

--best regards

[panman]

(The M 221 F had the capsule fittings and polarization scheme of the original M 221; its capsules won't fit on an M 221 B, and wouldn't perform properly even if you modified them to fit.

David, I agree the M221 and M221F capsules would not fit on an M221B, but I fail to see why they would not perform properly, if they were modified to fit, because they all are polarized 120V with the possible exception of the Siemens M221B (60V) you mentioned in an earlier thread.

[David Satz]

panman, you're right; I wrote that assuming that I was remembered correctly the voltages that the different capsule types were built for, but I really should have double-checked my notes before posting. I hate making mistakes of that kind, both because they're embarrassing and because they're completely avoidable. Thanks for the "catch".

In any case the { original M 221 and the M 221 F }, the { M 221 A and M 155 }, and the { M 221 B } series have three different thread specifications, and if you can directly attach a given M 221-series capsule to a given M 221-series amplifier, then the polarization voltage should be correct--again apart from those few, weird Siemens-branded 60-Volt M 221 Bs.