A Big Undertaking…Re-“Building”, Modding an Old API Console

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jsteiger

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A Big Undertaking…Re-“Building”, Modding an Old API Console

What’s up,

I’ve been conversing behind the scenes a lot about some of the projects I am working on. Specifically my duplication of the “line in” portion of an API 528/536 input module, fitted physically for use in the ¾” wide channels of the tape monitor bucket of my board. I figured I would share my stuff with the class for fun and maybe some inspiration. Dennis (Prodigy member “API”) and I have been talking for many, many months now about the monitor sections in our desks. I’m happy he keeps waiting for me! It will be worth it man! As of late, Dana W. (Prodigy member “Tubemooley”) and I have been emailing about console design, building and the like. I was telling Dana about my monitor project and promised some pics. I figured I would just do it in public for the world to see.

Here’s the background. I’ll try to keep it short to not bore anyone. Dana asked what all this business was about my “discrete monitor channels”. The monitor return cards in our desks were IC based. An obsolete Raytheon RC4739 dual opamp to be exact. IMO, they sounded a little crappy. The bottom end was rolled off when you get near 30hz. Plus, there was a  weird peak somewhere around 6K if I remember right. They had 2 Cues and 1 Echo, independent from the input Cue/Echo. When I got my board, it had 24 custom "discrete" cards. The boards were Brent Averill's work. Dale Epperson of OSA stuffed and installed them in the board for previous owner. The boards were trouble. Dremel marks everywhere plus they did not function well with the rest of the desk. At the time, early in my owning the desk, I had a local, very good tech coming out every month or two to test things, check out my work and what not and make sure I wasn’t f-in’ the whole thing up! I learned much from him. One day, we tried installing 2 of Dale's cards. One had a cap explode as soon as we power up the board. The other didn't pass audio. I had a couple of resistors literally fall of in my hand as a would pick up the cards. We both determined it would be cheaper to build new cards than try to debug those. Then there were the opamps, some were 2520's, some were the sea foam green OSA's and some where 5534's with the 22pf compensation cap. I sold them on eBay with a full disclaimer that they were shit and needed a lot of tech debugging. I hope whomever bought them doesn’t hate me but I was clear about them needing A LOT of TLC.

After that, I tried the original 812p's and found out that they left something to be desired. So, I got the great idea to essentially build the line part of the input channel for cards that fit in the monitor bucket. They have 4 Echo sends, 2 Cues, Stereo pan, mute, solo, phase, 3-pos HP filter and a 104mm P&G (Thanks to Colin, Slenderchap). The best part is they are sonically nearly indistinguishable from the input side.

API never had provisions to sum both sides together either. Mine will be able to combine any or all of the sends, cues and 2mix, or keep them separate. Much more flexible. Sonically, it really won't matter between monitor or input side, the sound at the 2 mix will be the same. That is the reason behind the Inv-ACA.

So, enough rambling, Here’s a few pics.
First, is the empty desk where the monitor bucket goes. All the ACA’s for this section will be rebuilt, that’s why one is missing. I have to either zinc plate or clear powder coat the shield under the ACA’s. See the rust!


Next, is the empty monitor bucket in place.


Next, is the bottom of the motherboard. I have reworked a lot of this for a few reasons. I have cut and separated the stereo bus tracks into 4 groups of 8. Those will be pre-summed thru my Inv-ACA’s before going to relays for routing of their signal to be summed thru the monitor 2-mix or being dumped to the main 2-mix.


The 4 strategically placed daughter boards are home for 32 of Ed’s 2623-1’s. This balances the preamp out of each channel before being sent to a future patchbay. Temporarily I will jumper(normal) the D-subs to each other until I can build a dozen or 2 of Peter’s 553’s!


The transformer, or EQ module on the input side, returns unbalanced to the channel card feeding the Cues and/or Echo’s if set to pre-fader, then directly drives the channel fader. This is precisely how it was done on the input side.


It’s a lot of iron with not much space to make it all work, plus standoff mount the boards and not have to drill thru a few traces! Channel frames were the only option.


So, here is one of my 2 proto channels. I have some changes to make on the board before going to production. The layout of the top 2 switches needs to be changed. I need to tweak the audio path layout so I can get the BC axials laying down. I went thru many different caps before settling on these. The 5534 is a balanced receiver for the signal coming from the input side (for metering only). The 741 is inverting for the meter buffer. That circuit needs to be redrawn for the components used in reality. The flying Xicon is only due to not having a 100uf radial on hand at the time.


Metal work is here. The L-brackets need to be zinced yet. The faceplates need to be powder coated a silk screened.


Lots of work no doubt. Will be well worth it if I ever get it finished :)

I honestly think this is what Brent had in mind when he had his boards done years ago. Not cheap but they sound killer. BTW, I have 6 or 8 of Brent's boards with no mask. Anyone who wants them can have them for the cost of the shipping. I have his schemo too.

Now you can see why I need so many damn knobs!!!

Maybe I am insane…
Cheers, Jeff
 
Its funny that you should mention the build quality on the OSA's.
When I was a student at CRAS in Tempe arizona Dale was the house
tech. He had students stuffing the PCB's for intern hours.
I can tell you that they do sound good when built properly but
quality control wasn't a company strong point.

Cheers

Good Luck restoring the beast!
 
At the time I heard the deal was, if you built ten or twelve you could have one to keep
plus the some hours towards your internship.

I think Dale was doing better at freelance work than doing stuff for OSA.
He was always on the phone with some one talking them off the edge.
Just as a side note, Although Dale was the house tech we always had The Desk
Doctor working on the SSL's And Neve's.

Cheers
 
Hello,

This is all so interesting, it truly is a small world. I hang out here at Prodigy Pro because I love building my own gear and everyone here is so professional and considerate. I stumbled across this thread because a great friend owns an API and I thought he would enjoy reading it.
Anyway, I read further and noticed the OSA, Dale E. and CRAS comments. I am heavily affiliated with CRAS and wanted to update a few things. As of January 2009, Dale was no longer the tech at CRAS. Dale occasionally used interested students at OSA and provided them with a bit of electronics experience. This was, and is, not part of CRAS' curriculum! We now have the wonderful and very talented Jeff Harris from the Village, LA. Dale is now concentrating 100% of his time to his company, OSA and we wish him all the luck. 

Cheers,
Tony
 

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