Gear / Technical Help > Microphones & Setup

AKG Repair Concern

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jmitchell:
I recently sent 2 c451e in for repair.  One of the pres "L" i knew had issues, but it wasn't a problem that i could consistently reproduce, so i sent a second pre "R" with it to see which one he felt needed the repairs.  At first, he felt  R was the one with the problem, the levels were considerably lower than L.  He said that he was able to adjust R to bring it more inline with L.  The next day he was able to get L act up and a transistor was replaced.  The problem i now have is that R appears out of phase.  I don't have the knowledge to explain to him exactly what the problem is.  He asked for samples and told me after listening the he didn't believe there was a problem.  The pictures below were then sent to him and i haven't gotten a response.  I have talked to a couple of folks and one said that the R was out back together incorrectly and that if I mounted the mic vertically instead of horizontally I should be able to correct the issue, but that isn't a fix.

noahbickart:
If you flip the phase of the "bad" microphone in post, does it solve your problem?

audBall:
Can you post a zoomed-in closeup of the waveform?

That could help us determine if there is a phase issue.

Out of phase would look similar to this:
L  /\/\
R  \/\/

As opposed to in phase:
L  /\/\
R  /\/\

I owned a pair of modded mics once that were wired back out of phase. It wasn't ideal, but I was able to easily fix this in post once the issue was known.

jmitchell:
That is exactly what it looks like.



I just got off the phone with him and he said he has never had anyone with this problem and he isn't sure how he can fix it.  I am sending them back to him because I don't know what else to do.

Gutbucket:
Along the same lines of questioning- What's the situational difference between the top image capture and the bottom image in your first post?

The lissajous displays seem to indicate and inverted-polarity situation in the top image, and a non-inverted-polarity situation in the bottom image.

The most recent zoomed-in photo you just posted shows inverted polarity between channels.

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