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 on: August 07, 2018, 11:21:27 am 
Started by John diggs - Last post by John diggs

Hi, i need the advice of more experienced people.

I acquired a pair of vintage akg c28-c (the nuvistor version).

They came from a guy who bought a broadcast lot a long time ago. They came without psu and connectors, they haven't been used in probably 20 years.

I had Leo Schall build me a psu and machined connectors
(Very well made!).

I have not tested them yet for fear of damaging critical components (like the transformer).

Is there any component i should test before applying power?  Critical resistors? Capacitors?  The 25uf cap is tantalum.


 on: August 05, 2018, 09:01:12 am 
Started by klaus - Last post by Hermetech Mastering
Just got a European/Tuchel pair of KM84s from 1977, and am presuming they have the 200 ohm outputs. Question is, regarding the mic pre, (a Chandler TG2 which has switchable input impedance), which setting will give me the flattest/best sound, 1200 ohm (standard) or 300 ohm? Have just been using 1200 so far and liking the results, but am about to ship the mics off to Andreas Grosser in Germany for a service. The 300 ohm setting is about 5dB louder on the same source, but am worried it won't sound as good/have higher noise/be less flat etc.

Theoretically, which setting would be best for these mics?

Thanks in advance,


 on: August 03, 2018, 07:16:57 pm 
Started by RuudNL - Last post by David Satz
I created the table that is in Brian Campbell's "Reply #1". It lists all the test parameters I could find in Neumann's InfoPool for microphones based on the K 67/87/870 capsule type. To my knowledge that's the only capsule type for which Neumann has built EQ into the amplifiers specifically to tailor the sound quality of the microphones, rather than simply to provide bandpass filtering--and that's why microphones such as the U 47 and U 89 were not included.

I think that the different design choices are interesting. Also, they should serve as a caution--for example, if you compare a U 87 with a U 67 or M 269 with the intention of hearing "the difference between tube sound and transistor sound" you will only fool yourself, and the table shows why.

BTW, Mr. Sattler's document was one of the sources for the table. It's listed as "docu0048.pdf" since that was its filename in the Neumann InfoPool.

--best regards

 on: August 03, 2018, 02:13:20 am 
Started by RuudNL - Last post by RuudNL
That is also an interesting one! Many thanks!
(I wasn't sure about the U47, it was a long time ago I saw it.)

 on: August 03, 2018, 12:00:41 am 
Started by RuudNL - Last post by uwe ret
Here is an older 'official' document for nearly all pre-1981 Neumann tube microphones and the first generation (T-powered 70-series FET series). Unfortunately it does not include the U47/U48...

 on: August 02, 2018, 01:49:44 pm 
Started by RuudNL - Last post by RuudNL
Yes that is the one! Thanks a million!!

 on: August 02, 2018, 11:27:11 am 
Started by RuudNL - Last post by Brian Campbell
This chart?

 on: August 02, 2018, 03:08:15 am 
Started by RuudNL - Last post by RuudNL
Some time ago, I found a document with an overview of the gain and de-emphasis of several Neumann microphones.
(The amplifier circuits.)
I am almost certain that it contained amongst others, the data of the U47, U87, U87ai and U89.
Unfortunately, it seems I can't find it anymore...
Who knows where to find this information?

 on: July 28, 2018, 01:03:52 am 
Started by klaus - Last post by gtoledo3
Very interesting, thanks for that response!

 on: July 28, 2018, 12:38:37 am 
Started by klaus - Last post by klaus
So, how do you test the diaphragm tension of an assembled capsule, or do you just listen empirically?
I listen.

It always seems a little circumspect to me to peg difference down to just that. Small differences in the size of holes in the backplate for instance, etc., could seemingly make as much difference in end frequency response.
I know it's the diaphragm tension, because once I relax an overly tight diaphragm, the capsule behaves and sounds just right. If it were something else, relaxing the diaphragm to levels of tension found in former times would not bring the capsule into compliance.

It also seems like low tension can be a bad thing... one of the first things to make a capsule sound bad, IMO, is low tension that starts to result in a capsule being overly sensitive to plosives.
Of course. I speculate that too many K870 were too close to that limit, so they were selected out and rejected, which cost the company too much money, which caused the company to increase diaphragm tension, which reduced the amount of rejects, but which made the capsules sound worse.

But what do I know? Could have just been a new tensioning weight they ordered that was off, or something else...

Pages: 1 ... 8 9 [10]