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[Noah Scot Snyder]

Well, the plot thickens. I received the M934A and it fits just fine. I believe that may mean these microphones are the same as the microphone pictured in both links I posted previously. No photoshopping, I assure you. I still keep thinking that these mics are some version of the m221. The only thing I think I can say for sure is that they seem to be rare microphones indeed and they sound amazing.

[Noah Scot Snyder]

...

[panman]

I believe that may mean these microphones are the same as the microphone pictured in both links I posted previously. No photoshopping, I assure you. I still keep thinking that these mics are some version of the m221.

It really seems to be as you say, but they are all M155:s, because mine is definitely M155 and the insides look the same. I never had a chance to see a M221A. Neither is there any info or schematics to be found. It begs for the conclusion, that M221A and M155 are the same mic in fact. Would be nice to know for sure, though it would make some of my previous statements invalid. Is there really nobody, that owns a M221A? As to the M934A, that you now have, looking the pic you posted, I clearly see the thread diameter beeing bigger than in mine. Yours is marked M934A, but as I now checked mine, it only has "Nr 457" written on it. My conclusion is, that the first badge limited amount M221(no A or B) is the rare odd-ball with smaller thread and M155 and M221A share the same housing-tube and thread size. This link shows Telefunken M221, that is the same as mine: http://www.filmsoundsweden.se/backspegel/schoeps.html. There again the capsule only has the sn. marked. I would post pics, but my camera-battery just went flat. Of course they are all versions of M221, but as the schematics show, they do differ some bit.
Inspired by this thread, I mounted the M155 innards into a M221B body with M934B. The M221B housing has a larger inner diameter, so the electronics stay a bit loose, but with the set-screws it was possible to get it tight enough to do some AB:ing against the M221 having that 934-type capsule. There is a noticeable difference in volume M221 beeing louder, but M155 has better bass-response also extending lower. Otherwise they did not really differ much sonically. Did not check the trafo wiring yet. Could be the 50 versus 200 ohm difference. M221 has the phase flipped for some reason that I cannot figure out. Perhaps the European versus American standards differing those days. From before I do remember M221B beeing slightly louder than M221 again.

[David Satz]

I have only limited information about this, but there definitely was a model M 221 A, as well as an original M 221 which was neither "A" nor "B", and finally a model "C" was manufactured as a small, final batch many years later. There are differences in the mechanical fittings of the capsules (threads inside the body sleeve vs. threads outside, differing in pitch as well) and in the "A" type, the polarization voltage was generally 60 Volts while in the "B" type it was generally 120.

However, there is at least one schematic published for the M 221 by Telefunken which seems to be a hybrid of "A" and "B" types. Perhaps as many as three variants of the "B" circuit were produced at different times. And the M 155 in general is very sparsely documented; I have never been able to find out why this model even existed as separate from the M 221 series. But so far as I know it was made exclusively for Telefunken, never for Siemens or Philips, and wasn't sold under the Schoeps label, either--so the answer probably lies in Telefunken's commercial concerns rather than anything on Schoeps' side of the arrangement.

Schoeps has only very limited internal documentation concerning many of their older products, the people who designed and built them are no longer available to be asked about them, and a fair amount of information has had to be reconstructed in retrospect. To complicate matters, Telefunken's documentation and product literature often doesn't track with Schoeps' as far as the use of the "A" and "B" is concerned, creating some curious anomalies and "time paradoxes".

This is about as much as I know on the subject. I get the impression that in these matters, one has to deal with whatever is in front of one's eyes and nose, and not try too hard to make it fit properly into any one, definite schema.

--best regards

[klaus]

...in the "A" type, the polarization voltage was generally 60 Volts while in the "B" type it was generally 120.

Are you sure? It's been a while since I worked on them, but I don't recall such high voltage on the capsule. Maybe you meant B+, rather than capsule polarization voltage?

[usattler]

According to the schematics posted in this thread and elsewhere, at least the Telefunken M155 and the Schoeps M221B have their capsule biased by 120 V, the Schoeps M221 and M221A feature a 2:1 voltage divider and bias their capsule with 60 V. That fact may also be responsible for the level difference observed in a previous post.

[Noah Scot Snyder]

Thank you all for sharing your fine thoughts. With your help I am continuing to learn about these microphones. I may yet be able to rely on them for recording.

[Noah Scot Snyder]

Just wanted to happily report after replacing a faulty power supply (evidently a capacitor problem) these mics are finally quiet enough for me to us recording orchestra. I deeply appreciate all your help and I'm both lucky and pleased that the mics themselves are in such good condition.

[klaus]

Thanks for your Abschlussreport!
KH

[Timjag]

Out of interest does Martin at Madooma have any info on them? I recently bought a NOS W28 windshield for C28A from him and he was extremely helpful. He clearly has his resources for finding all this (lovely) old junk, I would have thought he would have some history on them.

[klaus]

Why not ask him directly?

[Noah Scot Snyder]

I did ask Martin, and Andreas Grosser as well as Berhard Vollmer and many other sources that were all generous with their knowledge, but no one had any info on the CM9b capsules or this version of the 221. They do sound great and I like the M934A capsule as well. It sounds different from my M221B with 934B capsule but has its own beautiful tone.

[David Satz]

As an update and partial correction: The M 221 had numerous sub-types and variants, each with several types of interchangeable capsules available. There were two physical attachment schemes: The original M 221, the M 221 A and the M 221 F used coarse threads that faced outward on the capsule housing. The M 221 B used fine threads that faced outward on the amplifier housing, like those of the Colette series today.

Meanwhile, either 60-Volt or 120-Volt polarization was used in different models of the series: The original M 221, most M 221 B, and all M 221 F used the 120-Volt plate supply to polarize the capsules. The M 221 A, the M 155, and a few Siemens-labeled M 221 B amplifiers used a voltage divider to bring this voltage down to 60 V, and of course the corresponding capsules were built to operate at that lower voltage.

The threads of the M 221 A and M 155 may have differed enough from those of the original M 221 to prevent capsules of either type from being used on the other type's amplifiers; Telefunken's brochure for the M 221 A says as much, but I'm still looking to establish it for sure either way. Since the M 221 A and M 155 capsules were designed for 60 Volt polarization while the original M 221 supplied 120 Volts to the capsules, it would be very bad particularly if capsules of the later type could be used on the earlier type of amplifier.

--best regards

[David Satz]

I re-read the whole thread and would like to add some further details.

--The M 155 was a version of the M 221 A sold to German broadcast organizations. It was distributed mainly by Telefunken. The only difference in principle between the two types was in how the shield and ground were wired at the T 3402 output connector: In the M 221 A, pin 3 = ground and pin 6 = shield, while in the M 155, pin 6 was left unconnected and the shield was tied to ground on pin 3.

The M 155 officially had only three capsule types available, called M 155/1, M 155/2 and M 155/3 (designations which were also applied to the microphones as a whole in some listings). Those corresponded to the M 221 A capsules M 939a, M 939b and M 940 respectively. The M 939a was a fully diffuse-field-equalized, single-diaphragm pressure transducer (omnidirectional) for what would be considered distant placement by today's standards (e.g. one microphone placed so as to pick up an entire orchestra or other large ensemble in mono, in a concert hall with natural balance), while the M 939b was also a single-diaphragm omni, but more like the types used today for A/B or "Decca tree" stereo recording, where the placement is not as distant.

The M 940 was a single-diaphragm, single-pattern cardioid capsule with a permanently attached ring flush with the front of the capsule, which was still needed to achieve the specified front-back ratio at that time. No counterpart of the M 934a switchable, two-pattern capsule--the "normal" offering for the M 221 A--was offered for the M 155 at all.

--"CM 9" is an internal Schoeps designation for a single-pattern omni capsule of a certain generation. I suspect that the CM 9a might correspond to the M 939a while the CM 9b might correspond to the M 939b. Please don't hold me to that, but if it's correct, then Bernhard Vollmer's idea that it was a forerunner of the MK 22 would also be correct--and I always enjoy agreeing with him.

--The "M 211" microphone shown in some photos earlier in the thread appears to have been chopped and rebuilt from its original form, in which there would have been a semi-flexible gooseneck about 8" long built in between the amplifier body and the large, RF-proof Tuchel output connector. I don't believe that the "foot" with the output connector in the photos is original.

--Not mentioned previously in this thread, but just for the sake of completeness: The microphones which Schoeps made for French broadcasting (RTF) under the series name "CMMT 30" used M 221 A-type capsules.

--best regards

[panman]

David, thanks for reviving this thread and the incredible amount of new info!

You wrote:„I would also like to note that a fair amount of misinformation is evident in some of the messages.“

Perhaps you could be a bit more specific about it? I went through the thread, but was not able to find much except my initial assumption, that the pics the OP posted were M155:s, which proved not to be the case after seeing the pics in later postings, that made me suggest M155 is M221A. You finally confirmed, that they are "similar" except the way shield and ground were wired. I can confirm these differencies in my M155, but I do not have a M221A. However, my M221 has the same grounding scheme as M221A you mentioned. That means both schematics of M155 and M221, that I have posted in this thread have the grounds slightly wrong. I know it`s a long thread and and it`s hard to get all the details, but what else was misinformation, because „a fair amount of misinformation“ indicates there is some more? What did I miss?

Regarding the 60V/120V polarization, you say there is no way to know which. I find it hard to believe, that a company like Schoeps would take such a risk. In this thread I have pointed out, that the capsule-thread on the M221 is of a smaller diameter than the thread on the M155(M221A). I also posted pics from that. If  M155 and M221A are „identical“, that means there are three attachment-schemes for the capsules and not two. So, you cannot accidentally (or purpously) attach he capsule from M221A (M934a-60V) on the M221(120V)-body.  Schoeps surely did this on purpose. It remains the M221B, that according to you was sometimes polarized 60V, but mostly 120V. Based on what I wrote above, I would find it strange, that you really could mix 60 and 120V.capsules on M221B:s, but CV60/CM60 also came with 60 and 120V bodies and capsules and you can mix them. But at least they are sort of marked: 60V- capsules you can endlessly twist around, but 120V-capsules are fixed. One of the capsules I have turns around endlessly indicating a 60V-capsule, but inside it has a scratched writing: 120V, that is very hard to notice. Schoeps also marked the bodies with blue(120V) and red(60V) dots.