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Author Topic: Neumann U87Ai: Circuit Changes Through The Years  (Read 10343 times)

SergioA

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Neumann U87Ai: Circuit Changes Through The Years
« on: December 19, 2014, 02:35:43 AM »

After a long web search, came to the conclusion that there is not nice and clear info regarding all of the Ai incarnations. Here was noted the change for daughter board for replacing the now scarce jfet, using surface mount components. That was done when going from circuit 02 to 04. (KH: Wrong, the change happened between circuits 03 and 04).Now I understand there is a circuit 05. (Wrong again, 04 was replaced by 06; see last post in this thread)

No info on that. Not circuit wise, not sound wise. Also,would be interesting to ask if they continued making real good capaules since I recall a post from Klaus stating how good were the new k67s a year ago.
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Sergio Armes

klaus

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Re: Neumann U87Ai: Circuit Changes Through The Years
« Reply #1 on: December 21, 2014, 03:45:48 PM »

The sub-circuit board, consisting of five semi conductors and additional passive components, was introduced in 2002 with circuit #04. Circuit #03 which was superseded in 2002, still had one discrete FET only.

As to significant changes of the U87Ai from versions #1 through #3:
only minor changes/improvements were introduced, which do not affect the product audibly in any way: anything from better circuit tracing material, to changes in switch material to stamping the serial number into a different part of the bottom bell. The big audible change came with the introduction of the daughter board. The mic equipped with circuit 04 sounds a bit more fuzzy and unengaging.

2015 brought circuit version 06 to the U.S. Lowest serial number I recorded for 06 versions is 123xxx. Now we are back where we started: the good old 2N3819 FET, this time the Fairchild version, is once again individually biased, (it is also used in the new U47fet reissue) and the daughter board is gone. Big improvement.

I have recently posted about the K870 capsule quality issues in another thread.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

cdw

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Re: Neumann U87Ai: Circuit Changes Through The Years
« Reply #2 on: May 18, 2016, 12:55:22 PM »

I can confirm that a U87Ai with serial number as low as 12246x has the revision 06 circuit.  :D
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