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512c sounding thin and distorted Audio Interfaces
Old 29th April 2017
  #1
Gear Nut
512c sounding thin and distorted

Hi slutz,

I have two API 512c pres in an API lunchbox. I was using one of them to mic up a tom and noticed the sound was unusually thin. After testing a second of the same mic and going through all the possibilities, I've concluded it's an issue with the preamp.

This is my first pair of API pres and I'm wondering if anyone knows what might be an issue with a 512c that is passing signal, but just sounds thin and distorts way more easily than the other one beside it on the same source with same mic. Is this an op amp failure, or any other ideas?

Thanks
Old 29th April 2017
  #2
prob the opamp went dead, api is great for warranty....
Quote:
Originally Posted by brownj24 View Post
Hi slutz,

I have two API 512c pres in an API lunchbox. I was using one of them to mic up a tom and noticed the sound was unusually thin. After testing a second of the same mic and going through all the possibilities, I've concluded it's an issue with the preamp.

This is my first pair of API pres and I'm wondering if anyone knows what might be an issue with a 512c that is passing signal, but just sounds thin and distorts way more easily than the other one beside it on the same source with same mic. Is this an op amp failure, or any other ideas?

Thanks
Old 30th April 2017
  #3
Lives for gear
 
hasbeen's Avatar
Quote:
Originally Posted by vsthalion View Post
prob the opamp went dead, api is great for warranty....

Since you have a pair, try swapping the 2520 opamps.

Old 30th April 2017
  #4
Gear Nut
Quote:
Originally Posted by hasbeen View Post
Since you have a pair, try swapping the 2520 opamps.

Hey, is this easy to do? I've scoured the net and can't find anything. Is there soldering involved or is it simply pulling them out and plugging back in?

Thanks!
Old 30th April 2017
  #5
Lives for gear
 
hasbeen's Avatar
Quote:
Originally Posted by brownj24 View Post
Hey, is this easy to do? I've scoured the net and can't find anything. Is there soldering involved or is it simply pulling them out and plugging back in?

Thanks!
You got it! The opamps plug in to the board. The black cube that says 2520. Really easy. They have 6 pins similar to a vacuum tube.

Report back


Old 1st May 2017
  #6
Try exercising the switches on the front. Those switches on the 512s can get dirty and sometimes result in what you described.
Old 2nd May 2017
  #7
Gear Nut
Quote:
Originally Posted by hasbeen View Post
You got it! The opamps plug in to the board. The black cube that says 2520. Really easy. They have 6 pins similar to a vacuum tube.

Report back


Unfortunately, it's not the opamp. I switched them out and no change. Both opamps are working fine (the one from bad unit works fine in good unit), but the one pre is still distorting heavily and early and not in a pleasing way! Looks like I'll have to send into API for repair.
Old 2nd May 2017
  #8
Lives for gear
 
hasbeen's Avatar
Quote:
Originally Posted by brownj24 View Post
Unfortunately, it's not the opamp. I switched them out and no change. Both opamps are working fine (the one from bad unit works fine in good unit), but the one pre is still distorting heavily and early and not in a pleasing way! Looks like I'll have to send into API for repair.
One last thing to check is that all of the colored wires from the transformer are in good shape with a solid connection. Other than that Good Luck!

Old 2nd May 2017
  #9
Lives for gear
 
voodoo4u's Avatar
Visually inspect all the capacitors. Depending on how old the unit is and if it's been subjected to some high temperatures, they can sometimes leak and expand and just simply go way off spec. A bad cap can really thin out the sound.
Old 2nd May 2017
  #10
Did you flip the wiring from one pre to the other? To test the wiring? Or like the others said bad cap. Also try switching slots in your lunchbox
Quote:
Originally Posted by brownj24 View Post
Unfortunately, it's not the opamp. I switched them out and no change. Both opamps are working fine (the one from bad unit works fine in good unit), but the one pre is still distorting heavily and early and not in a pleasing way! Looks like I'll have to send into API for repair.
Old 2nd May 2017
  #11
Gear Nut
Quote:
Originally Posted by vsthalion View Post
Did you flip the wiring from one pre to the other? To test the wiring? Or like the others said bad cap. Also try switching slots in your lunchbox
I tried switching slots in the lunchbox to no avail. I'm not sure what you mean by flip the wiring? You mean where I'm pointing here?

https://drive.google.com/file/d/0Bx-...ew?usp=sharing
Old 2nd May 2017
  #12
Gear Nut
Quote:
Originally Posted by voodoo4u View Post
Visually inspect all the capacitors. Depending on how old the unit is and if it's been subjected to some high temperatures, they can sometimes leak and expand and just simply go way off spec. A bad cap can really thin out the sound.
All capacitors appear to be in good shape.
Old 12th May 2017
  #13
Gear Nut
audio repair in Toronto?

Does anyone know of anyone capable of troubleshooting/repairing audio gear in the Toronto area? Trying to avoid a lengthy shipping across the border to API to repair my 512c.
Old 12th May 2017
  #14
Studio economik in mtl can fix it
Give them a call
Quote:
Originally Posted by brownj24 View Post
Does anyone know of anyone capable of troubleshooting/repairing audio gear in the Toronto area? Trying to avoid a lengthy shipping across the border to API to repair my 512c.
Old 13th May 2017
  #15
Gear Nut
Solved

So after all that, I'm embarrassed to say that the 512c is working as it should and it's actually an issue on the first channel of my RME fireface 800. I'm using its A/D converters and going adat into my RME Babyface. Lesson learned: check the whole chain!

Thanks for trying to sort me out guys. Wanted to report back as both 512c pres have not let me down and I love them.
Old 13th May 2017
  #16
Lives for gear
 
voodoo4u's Avatar
Quote:
Originally Posted by brownj24 View Post
So after all that, I'm embarrassed to say that the 512c is working as it should and it's actually an issue on the first channel of my RME fireface 800. I'm using its A/D converters and going adat into my RME Babyface. Lesson learned: check the whole chain!

Thanks for trying to sort me out guys. Wanted to report back as both 512c pres have not let me down and I love them.
Thanks for being honest enough to admit when you get it wrong. When it comes to tracing a problem through a signal path, it's easy for all of us to get mush brain and forget to check all the details. We've all been there at some point.
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