User talk:Schroedere

Compander questions
Dear Ernst,

I hope you are doing well. As you might have seen I have been working on various compander-related articles over the years, but there are still some open questions for which I could not find answers myself researching the (available) literature. Nevertheless, for historical accuracy and completeness, I think, it would be great if the articles could cover these topics properly. As you are an expert on companders (and Telefunken ones in particular) I am reaching out to you in the hope you still remember some of those details after all these decades and even would have fun to answer them. So, here is my catalog of questions (there are more, but this is already a long list):


 * There was a telcom c4 variant for transmission lines with 2.5:1 (instead of the normal 1.5:1) compression ratio. Do you know when development started for this, and when it was introduced into the market. What was the achievable noise reduction in dB(A)?
 * Do you still remember the crossover frequencies of the High Com II and III compander systems?
 * The High Com II system spec'ed at 20–25 dB(A) noise reduction; was the (commercially unreleased) High Com III system even better in regard to the noise reduction figure, or was it just acoustically superior to II due to its three-band character?
 * Did the III system also use pre-/deemphasis or not?
 * In order to develop high-quality DSP/software-based expanders for recordings in the various High Com schemes (and not only some vague approximations), do you still remember the other system parameters like the various time constants and pre-/deemphasis values used in the system? I could find some such values mentioned occasionally in the literature, but the exact context was not clear so I am hesistant to add them to the article. I think this needs someone who "sees" them in context (like you) and therefore knows exactly what would be necessary to know for independent parties to accurately recreate these expanders in software.
 * Was there ever a leader-tape color code defined for High Com (any variant)?
 * What was the compression ratio of High Com FM?
 * Do you have a datasheet for the TFK U2141B for CX? Do you know which expanders actually used this particular chip?

Thanks so much for your time.

Best regards, Matthias --Matthiaspaul (talk) 09:37, 17 June 2021 (UTC)