Become a Site Supporter and Never see Ads again!

Author Topic: AKG Repair Concern  (Read 1297 times)

0 Members and 1 Guest are viewing this topic.

Offline jmitchell

  • Trade Count: (1)
  • Taperssection Regular
  • **
  • Posts: 74
AKG Repair Concern
« on: December 13, 2017, 07:57:46 AM »
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.




Offline noahbickart

  • Site Supporter
  • Trade Count: (28)
  • Taperssection All-Star
  • *
  • Posts: 1667
  • Gender: Male
  • So now I wander over grounds of light...
Re: AKG Repair Concern
« Reply #1 on: December 13, 2017, 08:47:59 AM »
If you flip the phase of the "bad" microphone in post, does it solve your problem?
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Naiant Littlebox, Naiant IPA, Naiant PFA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10
Home Playback: Mytek DSD 192> Adcom SLC 505> Marantz Ma500 (x2)> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-400
Office Playback: Grace m903> AKG k701

Offline audBall

  • Trade Count: (34)
  • Needs to get out more...
  • Posts: 5734
  • Gender: Male
Re: AKG Repair Concern
« Reply #2 on: December 13, 2017, 09:19:37 AM »
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.

Offline jmitchell

  • Trade Count: (1)
  • Taperssection Regular
  • **
  • Posts: 74
Re: AKG Repair Concern
« Reply #3 on: December 13, 2017, 10:56:03 AM »
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.

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 11720
  • Gender: Male
Re: AKG Repair Concern
« Reply #4 on: December 13, 2017, 10:59:30 AM »
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.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 11720
  • Gender: Male
Re: AKG Repair Concern
« Reply #5 on: December 13, 2017, 11:02:11 AM »
Could it be nothing more than a miswired XLR with leads crossed between pin 2 and pin 3?
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline audBall

  • Trade Count: (34)
  • Needs to get out more...
  • Posts: 5734
  • Gender: Male
Re: AKG Repair Concern
« Reply #6 on: December 13, 2017, 11:24:20 AM »
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. 

Offline jmitchell

  • Trade Count: (1)
  • Taperssection Regular
  • **
  • Posts: 74
Re: AKG Repair Concern
« Reply #7 on: December 13, 2017, 11:33:48 AM »
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. 

Quote
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.

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 11720
  • Gender: Male
Re: AKG Repair Concern
« Reply #8 on: December 13, 2017, 11:53:37 AM »
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?
Quote
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?
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline jmitchell

  • Trade Count: (1)
  • Taperssection Regular
  • **
  • Posts: 74
Re: AKG Repair Concern
« Reply #9 on: December 13, 2017, 06:23:12 PM »
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?
Quote
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.

Offline audBall

  • Trade Count: (34)
  • Needs to get out more...
  • Posts: 5734
  • Gender: Male
Re: AKG Repair Concern
« Reply #10 on: December 13, 2017, 06:33:18 PM »
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.


Offline jcable77

  • Trade Count: (4)
  • Taperssection Member
  • ***
  • Posts: 307
  • Gender: Male
  • Needs to stay in more
Re: AKG Repair Concern
« Reply #11 on: December 13, 2017, 07:04:59 PM »
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.
Mics- AKG 460's/480's ck 61's/63's, Busman BSC1's k1,2,3,4, akg active  couplings>naiant pfa's, naiant x-r's (cards,omnis). Pre- SD-302, naiant x-y amp, apogee mini-me X2, Lunatech V-3, Decks- R-44, dr-40,dr-100mkiii,  dr-03.....

ISO- pair of ADK a51 tl's

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 11720
  • Gender: Male
Re: AKG Repair Concern
« Reply #12 on: December 13, 2017, 07:07:18 PM »
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.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Gordon

  • Trade Count: (18)
  • Needs to get out more...
  • *****
  • Posts: 10221
  • Gender: Male
    • my list
Re: AKG Repair Concern
« Reply #13 on: December 13, 2017, 07:19:39 PM »
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).
Neumann ak40 > Nick mod lc3 > Naiant PFA or km140 > Sound Devices MixPre-6

https://archive.org/details/fav-gordonlw

Offline jmitchell

  • Trade Count: (1)
  • Taperssection Regular
  • **
  • Posts: 74
Re: AKG Repair Concern
« Reply #14 on: December 13, 2017, 08:03:47 PM »
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.

 

RSS | Mobile
Page created in 0.255 seconds with 37 queries.
© 2002-2018 Taperssection.com
Powered by SMF
Website Design by Foxtrot Media, Inc., a Baltimore Website Company