API 525 linking - Gearspace.com
The No.1 Website for Pro Audio
API 525 linking
Old 9th August 2005
Deleted 6f6e2d3
API 525 linking


I've tried contacting API by email without luck and will try calling tomorrow but I need to find the final words on stereo linking a pair of 525 reissues.

I've heard a simple switch between pins 6 will do. I've also seen a resistor suggested there. I don't have any documentation but looking at the 525's I don't see any traces on the PCB's going to pin 6!

They are from 1998 serial numbers 90 and 91. I'm assuming there was no change in the reissue model's pin layout, unlike them compared to the originals?

Old 9th August 2005
Lives for gear
max cooper's Avatar
🎧 15 years
I've got the info; check your PM.

Someone replied here long ago thus:

"By connecting a switch between pin 11 of the two edge connectors ("side chain in"), you can have a switchable stereo link."

But what I have only mentions 7 & 8.
Old 9th August 2005 | Show parent
Gear Maniac
🎧 15 years
BTW I'm pretty sure the original 525s did have a different pinout than new ones. The originals were not compatible pinout-wise with 512s or 550s. They could be made so, but were not compatible from the factory. I believe Paul W. changed that so that all API modules could work in any slot in an API rack without repinning.

If they're from '98, I would make sure that you work off of new documentation.

Old 10th August 2005 | Show parent
Lives for gear
audioez's Avatar
🎧 15 years
if you were sucessful at getting through(to api), the end result would be an email from the head tonto at api...cheers
Old 13th August 2005 | Show parent
Lives for gear
max cooper's Avatar
🎧 15 years
I've got that email too, but there's a little doubt about the info; I wonder if the fact that there's reference to norm/stereo/quad switch means that this is how it's done in a console.

Apparently Brent Averill says to connect pins 6; another source (who seems highly credible to me) says to "tie pin 6 from one unit to the next through a 120 ohm resistor".

Then, of course, there's the reference to pin 11.

I'd sure like to get to the bottom of this before I 'go in'.
Old 13th August 2005 | Show parent
Deleted 6f6e2d3
I have this from a credible and experienced but anonymous source:
"The new 525 has pin 6 designated as the stereo link. The old 525 has pin 7 as the link."

I'm looking physically at my 525's right now and here's the layout:

pin 1 Chassis
pin 2 +OUT +4
pin 3 +OUT +4
pin 4 -OUT +4
pin 5 AUD GND
pin 6 N/C
pin 7 SC IN
pin 8 -IN+4
pin 9 SC OUT
pin 10 +IN +4
pin 11 AUD GND
pin 12 +16VDC
pin 13 PWR GND
pin 14 -16VDC
pin 15 48V (512B)

From the pdf it suggests a switch between pin 7's with a 120 ohm resistor between. It also suggests a connection between pin 7 and 8 when switch is breaking pin 7's. This isn't needed as far as I know since it looks like there is a trace on the PCB between pins 7 and 8.

There is no trace on the board to pin 6 and the N/C seems to verify this. Either mine from 1998 isn't considered "new" or the modern 525 never had pin 6 for a stereo link.

I guess this means the resistor and switch between pin 7's is all that's needed.
Old 14th August 2005 | Show parent
Deleted 6f6e2d3
It would seem that the pdf posted here by audioez is correct. Pin 7's connected by a switch with 120 ohms in between. I just tried it and it works.

Don't know where the myth of pin 6 came from if the old ones were pin 11...
Old 16th August 2005 | Show parent
Deleted 6f6e2d3
OK, the switch between pin 7's is definitely NOT working. I was in a pinch to finish a drum mix and didn't test it properly. It worked in dual mono the whole time. When I was done I looked harder at the stereo interaction and it's not happening.

Well, I just got off the phone with API and they pointed me to their website setup sheet:


Obviously points to pin 6! There DOES need to be a 120 ohm resistor between the pins too.

Man, I totally missed this when I looked there. Their engineer says any 525 made after 1980 would reflect this. Their support guy pulled out an actual current 525 reissue and looked at it. He suggests the "N/C" silkscreen on my pin 6 (and the 525 in his hand) is probably generic and doesn't apply to the 525, rather the 560b.

I'm at work right now so I can't check but he confirmed there is a trace to pin 6, I thought there wasn't. It sounded from his description that my 1998 reissues and the ones in his hands were identical.

Anyways, there's the heads up and I'll be trying pin 6 with a resistor between tonight and report back.

Old 16th August 2005 | Show parent
Lives for gear
audioez's Avatar
🎧 15 years
you guys might already know this, but the comps need to be set up in duplicate fashion.
Old 16th August 2005 | Show parent
Deleted 6f6e2d3
Yes, the settings need to be identical but I should see action on both meters with one side working, correct?
Old 17th August 2005 | Show parent
Lives for gear
audioez's Avatar
🎧 15 years
The 525 doesn't function like a Smart or 33609 comp/limit when in stereo mode, in regards to logic controls.

I own two 525 in a horizontial rack, which uses a single guitar cable to link the detectors together, end of story...it's just simple.

Where an original EL8 uses two guitar cables to achieve a stereo link
Old 20th December 2013 | Show parent
Lives for gear
666666's Avatar
1 Review written
🎧 15 years
Originally Posted by wilcofan ➡️

...There DOES need to be a 120 ohm resistor between the pins too...

Why? Just curious.
📝 Reply

Similar Threads

Thread / Thread Starter Replies / Views Last Post
replies: 8 views: 7756
Avatar for GlitterBalls
GlitterBalls 22nd January 2014
replies: 23 views: 2316
Avatar for RussianRecording
RussianRecording 7th December 2010
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.

Slide to join now Processing…

Forum Jump
Forum Jump