R/E/P > Klaus Heyne's Mic Lab Stickies

U87Ai Circuit Versions Explained

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klaus:
I had mentioned the U87Ai circuit changes in previous posts here and there.
Here is a comprehensive chart that you can copy and save, so you will know which circuit is in your mic (silver sticker with circuit # is on the back of every transformer):

Circuit Diagrams:
02: Standard-U87A Neumann (FET: 2N3819 or similar, selected)
03: DC/DC-converter board: omit U89 components (from ~1995)
04: PCB 4 in place of discontinued FET (from 2002 to 08/2013)
05: 2 values of components on DC/DC-converter board changed (2011)
06: return to single FET in place of daughter board PCB 4; DC board
same as 03, plus changes from 05. (since 08/2013)

As you can see, ONLY #04 and #05 have the dreaded "daughter" board installed, instead of the single FET.

RuudNL:
I think you mean 2N3819, not SK.
Thanks! Corrected. KH

afterlifestudios:
Thanks.

skrimoblee:
Will someone with experience share their preference and describe the sound of u87Ai's with circuit versions 02 and 06.

https://gearspace.com/board/high-end/1278068-u87ai-difference-different-vintages.html

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