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Neumann u87ai Circuit 02 vs Circuit 04
Old 19th January 2019
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ctcwired's Avatar
Neumann u87ai Circuit 02 vs Circuit 04

Hello all! This is my first Gearslutz post, though I've been a reader for ages.

My mics: For my radio & podcast studio I've acquired two Neumann u 87 ai mics, one which is from the early 90s and has circuit type 02 and another which is from the mid 2000s and has circuit type 04 (with the small extra sub-board PCB located near the top.)

I did send the older one in to Sennheiser to be cleaned & tuned up about a year ago, though I'm not sure if they truly verified that all parts were performing optimally or just simply cleaned the capsule.

Circuit Info: From reading online, people tend to say the 02 and 03 variants are more "mid forward" and "honky" while the newer (though not latest) 04 and 05 circuits are more "buzzy" and "airy." This temporary change to the design was made in 2002 due to discontinued parts required in the circuit. I believe after around 2013 Neumann has returned to the older design once they were able to source an appropriate part.

Circuit Diagrams:
02: Standard-U87A Neumann (FET: 2SK10x selected)
03: DC/DC-converter board without those components only required for U89 (from ~1995)
04: with additional 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; same as Circ.Diag.03, plus changes from 05. (since 08/2013)

The Test: Positioned with the baskets a millimeter apart and the capsules at the same height, both mics ran down the same brand and length of cable into an RME Fireface UFX with the input gain set digitally at 30dB. Cardioid mode, no pads or filters. Included is a talking segment, a silence segment and a pink noise segment.

In the wav files there is a gain difference of a few dB so I recommend normalizing the samples before comparing in your DAW.

Here's a quick screenshot of Fabfilter Pro-Q 3 running the match feature. The white line is what Pro-Q wants to apply to the circuit 02 mic to make it match the 04 mic.

Link to original wav audio samples including silence & pink noise: Dropbox - u87-circuit-compare - Simplify your life

Let me know what you think or if I should test anything else. I'm thinking I might try to trade one of them so I have a matching set.

Last edited by ctcwired; 19th January 2019 at 08:25 PM.. Reason: Added normalized MP3 versions
Old 18th October 2020
Lives for gear
JblKid95's Avatar
🎧 10 years
This might be true! I experienced something like this. I think mine is circuit diagram 6 and I can’t relate with anything bad said about an AI. There was also a very long time where there were no circuit diagrams but a chip instead for about ten years. Those ones to me sound fuzzy and lacked soul imo. Had it for about a year and couldn’t get it to sit right in a mix until I learned that others had this issue, so I bought one used and one new at the time to do a shoot out with all three. Long story short. I have never loved a mic like I do my u87ai. My u87 is a little dull compared to most 87s. Feels like the same mids of the 70s but more real and more air. Capsule might be at play here so it could still be a mystery. The 87s with more honk also sound incredible to me because the have a really euphoric sound if you know how to deal with it. The one with the pcb is a no go for me
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