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Gear / Technical Help => Microphones & Setup => Topic started by: jmitchell on December 13, 2017, 07:57:46 AM
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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.
(https://i.imgur.com/uWKB1nG.jpg)
(https://i.imgur.com/EaE9D22.jpg)
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If you flip the phase of the "bad" microphone in post, does it solve your problem?
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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.
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That is exactly what it looks like.
(https://i.imgur.com/Gaesis7.jpg)
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.
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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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Could it be nothing more than a miswired XLR with leads crossed between pin 2 and pin 3?
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Could it be nothing more than a miswired XLR with leads crossed between pin 2 and pin 3?
That would be my guess. If so, that's a simple fix physically, or in post production if you can live with it and want to avoid sending them back.
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Could it be nothing more than a miswired XLR with leads crossed between pin 2 and pin 3?
That would be my guess. If so, that's a simple fix physically, or in post production if you can live with it and want to avoid sending them back.
I do not believe that is the problem. I just now recreated the problem to make sure that was not the case. I also changed bodies and caps to make sure the same results were visable, and they are. The top 2 images (171207_037_st12 & 171207_037_st34) are for the graphs in the bottom right. Again, I don't know anything about this stuff, I just know something is not right. I sent him mp3 samples and he said he couldn't hear a difference so I took these screenshots to show that there is something out of line. The st12 are ck1 and the st34 are ck3. I just track both recordings at the same time, saves time I think.
and inverted-polarity situation in the top image, and a non-inverted-polarity situation in the bottom image
That is what I am looking for, someone to help me put names to what is going on. Thanks.
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I do not believe that is the problem. I just now recreated the problem to make sure that was not the case.
What did you do to confirm that?
I also changed bodies and caps to make sure the same results were visable, and they are.
When swapping amplifier bodies between left and right channels, does the polarity-inversion switch channels along with the amplifier bodies?
When swapping caps between amplifier bodies (but not swapping the amplifiers themselves between left and right channels) does the polarity inversion still swap channels?
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I do not believe that is the problem. I just now recreated the problem to make sure that was not the case.
What did you do to confirm that?
I also changed bodies and caps to make sure the same results were visable, and they are.
When swapping amplifier bodies between left and right channels, does the polarity-inversion switch channels along with the amplifier bodies?
When swapping caps between amplifier bodies (but not swapping the amplifiers themselves between left and right channels) does the polarity inversion still swap channels?
Are you talking about the xlr on the Pre or cable? If the cable, yes i did try a different cable. If you are referring to the connection on the pre no i have no way to test that.
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What gut and I are suggesting is that with the repairs to one of the 451 preamplifiers, the person who fixed them rewired the pin connections 2 and 3 opposite with respect to the other preamplifier. That is what is generating the inverted phase of the waveforms you are seeing.
It's not a big deal. You can simply invert the phase of one channel in post production from now on, zoom into the wave form to confirm that they align with one another, or send the preamps back so that he can swap the pin wiring so they match.
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Sorry to hijack this thread but just sent two 460 bodies to Lands yesterday. Was that a bad idea? Is that where yours went JM? Kind of got mixed signals from previous threads on the subject.
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audBall sums it up well above.
I was referring to keeping everything in place and the same, except swapping the microphone amplifier-bodies back and forth from the left to right channel and vice-versa. If the inverted polarity moves with the microphone body, that's were the issue is.
Leaving the amplifier bodies in place and swapping just the capsules back and forth would let you know if it's one of the capsules rather than one of the amplifier-bodies, but I suspect it's one of the amplifier bodies, with the simple mis-wiring problem audBall notes above.
Once you determine that, record a single hand-clap using both microphones. Zoom in with your editor to see which microphone shows the first cycle at the very beginning of the clap waveform going down instead of going up. That's the one with the inverted polarity problem. Mark that mic so you'll know which channel to invert when editing, or send that mic to your tech and ask him to check the wiring to pins 2 and 3 of the microphone's XLR connector. He probably just needs to switch the wiring to those two pins.
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No way he should have to fix this in post from here on out! Send them back to Land to fix his mistake (for free of course).
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Sorry to hijack this thread but just sent two 460 bodies to Lands yesterday. Was that a bad idea? Is that where yours went JM? Kind of got mixed signals from previous threads on the subject.
I don't know anyone else that can diagnose and fix them. If this gets cleaned up nicely, I will be happy. I have used him before and had good results. Folks make mistakes, how it is handled is what is important to me.
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Im in the same boat. Seems like the only option. I hope it works out for you and hopefully my situation can be resolved as well. Same thing, one body has a super low output. Ive been stalling sending them as i have others to use. Ill keep an eye out on this thread and see how things go. Post what happens with mine too.
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I got my mics back today, and everything seems to be working correctly. I will say that I am not happy with the service that I received. I spent nearly $400 to replace the damaged parts in two of my akg451 pres. When I got the mics back the first time, they were working, but one of them had inverted phase. I have not done any work on the mics myself, and the only person that has been inside of them was Richard. At first he did not believe there was an issue even with all of the images that were sent and he was adamant that this was not done at his shop. I asked him to take another look, and he did. He switched a couple of the wires in the xlr connection and wanted to charge me another $97 + shipping. I balked at having to pay anything and he gave me a, "Whatever Jeff" and ended the call.
Bottom line is mics are working properly, and he ended up doing the right thing in the end.
If anyone has any contact info for someone who can work on AKGs please let us know.
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Sorry to hear of your problems with Land. My experience was not any better, lucky for me my credit card sided with me :guitarist:. I would always try AKG USA first.
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Same mic, same problem. $400 down the toilet. I might as well walk around and give money to everyone i pass. Incredibly irritated.
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The AKG development crew seems like they got shafted in the Samsung buyout, but they have a new company and one of the guys apparently is servicing old mics. Not sure how busy or approachable he is, but might be worth looking into for anyone with AKGs that need work.
https://www.austrian.audio/single-post/mikrophonservice
Contact info (it's in German, they say they're working on an english translation): http://mikrofonservice.at/contact.html
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Sorry to hear about your recurring mic troubles. One would think that there would be a competent mic technician in the USA that could provide reliable service for your AKG mic pre's.
I think that it would be worth contacting Mike Amon, the AKG tech person mentioned above just to see if he would be willing to have a look at your mic body. The cost for insuring and shipping gear to Europe for servicing isn't cheap but it may be the best option for you at this point.
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I appreciate the into, but I think i am just about done with these mics. I could have gotten some off ebay for the money I have recently put into these. I just at the point of getting something new.
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Time to get funken!
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:coolguy:
Time to get funken!
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I hear your frustration.
Would be nice to keep the 451's though.
Lot of nice capsules fit on those, including ck22 omnis, ck8 shotguns, and other stuff too
I just bought a pair of ck8 and reducer rings so I can run them on my 460 bodies.
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I have four 451s, 2 ck1, 2 ck3, and 2 ck22, and 2 reducer rings. I just can't justify spending more on them. I've sent my mics to Richard 3 times now. I'll keep a working pair and all the caps to run a set.
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I have four 451s, 2 ck1, 2 ck3, and 2 ck22, and 2 reducer rings. I just can't justify spending more on them. I've sent my mics to Richard 3 times now. I'll keep a working pair and all the caps to run a set.
I guess you've got it covered then!
LOL. So far I've got bodies 460x3, Naint (sp?) actives x2 , and a pair of reducer rings,
Capsules: ck63x2, ck8x2, ck9x3 (long shotguns)
I agree, sending for repair is not worth it, but collecting, there is no cure for that.
Richard