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21
Klaus Heyne's Mic Lab / Re: Schoeps m221b transformer
« Last post by David Satz on June 06, 2018, 06:27:42 pm »
The original M 221 (1955) used a transformer designated as T 43, while the M 221 A (1956) used the T 44/1. The change from the latter to the A 925 appears to have occurred in about 1958; documentation in July of that year (M 221 F = version with Sogie output connector, made specifically for the French radio) shows "old" and "new" amplifier schematics (SB 92 and SB 93) with these two transformer types respectively.

After that, the A 925 is still shown in M 221 parts lists dated 1961, 1962, and even as late as September, 1971--and I don't have any Schoeps schematics or parts lists that refer to any "A700" transformer at all. That certainly doesn't mean that it never existed; there are significant gaps in Schoeps' own documentation from that period, let alone my subset of it. But I just don't see any reference to it.

--While interviewing people at Schoeps about the history of the company, I was told that Schoeps themselves had wound the transformers for the M 221 series, assigned individual serial numbers to them (!), and tested them individually to find the ones with the lowest distortion (said to be largely a function of how accurately the core laminations could be aligned). But I don't know whether this statement applied only to the A 925 (for example), or whether it applied to the other transformer types used in the M 221 series.

--best regards
22
Klaus Heyne's Mic Lab / Schoeps m221b transformer
« Last post by afterlifestudios on June 06, 2018, 10:54:03 am »
Most of the Schoeps m221's I've seen (including my own pair) employ an "A925" output transformer.  I've recently come across one containing an "A700" transformer. Does anyone have any info about the differences or the history on this topic?
Thanks in advance,
John
23
Klaus Heyne's Mic Lab / Re: U67: Add More Top End?
« Last post by Brian Campbell on June 05, 2018, 10:27:57 am »
thank you
24
Klaus Heyne's Mic Lab / Re: U67: Add More Top End?
« Last post by klaus on June 04, 2018, 09:19:07 pm »
As the test input only measures amplifier performance, without taking the variables of a hand-made capsule into consideration, it was probably the sum of all amplifier components-passive, tube, transformer- affecting the high frequencies. Hence a simple way was found to keep the highs within specs during final testing and adjusting.

You asked the same question on another forum, where at least one person speculated that the U67's transformer was so complicated that an adjustment for its variations in HF transmission alone would be necessary. I have my doubts as all C17 installed in U67 of a given period were always of the same value: either 80pf or 100pf (nothing above 100pf was ever installed in U67 I have seen).

Both values are so close, that I rather believe C17 was another way to show the German broadcast brown-book folks that the mic can be quickly adapted to their strict HF cut requirements. As the feature was retained in the broadcast version of the U67, it might have helped in the end to pass the mic. (All of this is just more speculation, I am afraid)
25
Klaus Heyne's Mic Lab / Re: U67: Add More Top End?
« Last post by Brian Campbell on June 04, 2018, 08:04:21 pm »
In the U67 schematics,  C17 is shown as variable 80-160pf. Is this to allow for variables in capsule, transformer or both?
Also what would be the range of frequency change with these values?
26
Klaus Heyne's Mic Lab / Re: What happened to the Neumann forum?
« Last post by klaus on June 03, 2018, 01:18:21 pm »
Super resource. Thank you!
27
Klaus Heyne's Mic Lab / Re: What happened to the Neumann forum?
« Last post by RuudNL on June 03, 2018, 03:16:28 am »
I found that the 'wayback machine' still has a backup of older postings on the forum:
https://web.archive.org/web/20160322054045/http://www.neumann.com/forums/list.php?lang=en&site=neumann&bn=neumann_mictec
28
Klaus Heyne's Mic Lab / Re: What happened to the Neumann forum?
« Last post by David Satz on June 02, 2018, 08:08:30 pm »
The word "hack" can have various shades of meaning. No doubt this was an intentional attack, but I saw no sign that the site's security was breached. It was apparently perfectly "legal," software-wise, for a malicious user to post multiple SPAM messages in rapid succession. And that appears to have been done via multiple accounts. But it didn't require any violation of technical boundaries--just boundaries of honor. That's why I wouldn't call it "hacking"--the forum software (and/or the way it was configured) allowed this incident to occur without any infiltration of the site's resources.

The forum software appears not to have restricted the number of (possibly automated) postings that it would accept within any given period of time. That is an available administrative setting in any halfway modern forum software that a Web site might use. I'm sure that this forum has similar settings, as well as some way to notify the on-duty admin if the set limit is suddenly reached, since that indicates that an attack may well be underway.

Maybe someone in Berlin was too trusting--honest people tend to expect honest behavior from others, no? The forums were the only feature through which content could appear publicly on the site without passing through any vetting on Neumann's part, and (to my knowledge) very few abuses had occurred in the 20 years before. But the entire Internet "ecosphere" has become a very hostile, hazardous environment. I believe Neumann uses a third-party service to host their Web presence, and perhaps there's some egg on the face of that service at this point.

The need to tighten up such controls--and the entirely reasonable fear that someone, somewhere will some day find another way to attack the site--is further reason for Neumann to be cautious about restarting the forums, which were the only area of Neumann's Web site vulnerable to spurious postings.

--best regards
29
Klaus Heyne's Mic Lab / Re: What happened to the Neumann forum?
« Last post by klaus on June 02, 2018, 03:50:43 pm »
Thanks for correcting my post regarding language characters, month of hack and number of forums affected.

I disagree with your notion that this was not a hack. I regard any intentional disruption of a website that results in its dysfuntion-whether through publicly accessible means or through breaking and entering- as a hack.
30
Klaus Heyne's Mic Lab / Re: What happened to the Neumann forum?
« Last post by David Satz on June 02, 2018, 03:06:39 pm »
Some 28,000 messages, containing mainly Korean characters, were posted in several bursts during mid-November, affecting three of the four forums. All the prior, human-written messages remained in place, but those became difficult to access since so many SPAM messages were queued in front of them. From all I could see, the three forums were never hacked as such, but rather were defaced by the sheer number of the mechanized postings. The fourth forum was an archive compiled internally at Neumann which was "read only" to the general public, protecting it in this case.

Soon Neumann locked all four of the forums, preventing further posts. They left the contents, including the SPAM messages, visible for several months on the old URLs. In the meantime a major update of the Neumann Web site was already underway, and when that new version was rolled out early last month, the forums were taken off line.

Back in December/January I corresponded with the folks at Neumann/Berlin about this; I'd written some custom software that compiled a list of exactly which posts were SPAM and which ones were valid. I don't have specific permission to quote their reply, but at the time they were evidently considering some new arrangement for on-line technical discussions, and in any case they emphasized that all customers are welcome to write to them directly with questions.

I haven't wanted to be a noodge, so I haven't written back for an update. Maybe someone else here has heard from them more recently. But I'm not holding my breath. The forum took up a fair amount of Martin Schneider's time sometimes, and he's one of their leading product development engineers; no matter how much he enjoys dealing with the public (in at least four languages!), that use of his time had to be justified as a rational business decision. The forums were certainly interesting for some number of us, but Neumann is (gasp) part of a for-profit corporation that is responsible to its shareholders, and its business decisions may not be 100% identical to our wishes in all cases.

--best regards
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