[BUILD]CAPI 2-ACA-Bo~Official Support Thread

jsteiger said:

It may be easier to understand a quick sketch rather than your circuit description.

Its possible that the 192 does not like being unbalanced? Maybe using an INA134 as a unity gain balanced to unbalanced receiver might be a better solution.

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I'm not really into It This week, but i'll have à Closer look on next week and come back here..!
Many thanks for you help!!

Hi Guys! I would like some help trouble shooting.
I finished building the 2 Channel ACA & Booster.
I tested the output of both channels going onto a RME FF800 interface.
the right side is very quiet but the left side is hissing, even when there is no input.
I have shorted the talk back FET. Still the same. is it suppose to hiss due to aplification?
Should I use 28K ohm for feed back? please help.

Paul Tong said:

Hi Guys! I would like some help trouble shooting.
I finished building the 2 Channel ACA & Booster.
I tested the output of both channels going onto a RME FF800 interface.
the right side is very quiet but the left side is hissing, even when there is no input.
I have shorted the talk back FET. Still the same. is it suppose to hiss due to aplification?
Should I use 28K ohm for feed back? please help.

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There should generally be very little noise and both stereo channels should behave the same.

When you say "left side" do you mean the 2 left channels on the PCB which are L/R ACA's or do you mean the 2-stage Left channel circuit as opposed to the 2-stage Right channel?

Either way, the very first thing to do would be rule out opamps...if they were built from kits.

ok let me recheck the opamps.

Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks

orangerec said:

Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks

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What is the part # and how are you measuring? I don't think they made a 4k fader.

orangerec said:

Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks

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Per the pics you emailed me, the P&G part # is 1122C. The "C" designates a  5k value. That said, I think you are fine using the R's suggested for a 10k fader.

Hi Jeffrey and all,

I just ordered the ACA-BO, and I have a few questions.  Thanks for indulging me.

I have read this entire thread, and gleaned lots of good information.  To help myself and others learn, it might be nice to write out a more conceptual, step by step overview of upgrading the Summing Buss in a mid level console:

Soundtracs Topaz

Topaz Power Supply is +/-17V, and I just totally rebuilt it.  I'm hoping there wont be a problem with using it to power the ACA-BO.  It is rated 1.5 Amps for 24 channel and 2.3 Amps for 32 channel.  Thoughts?

Looking at the channel LR assign section on the input PCB schematic, I appears the Topaz's buss resistors are 22K.

As per your suggestions on this Build Thread, with 22k bus R's, I will change R10 and R13 from 28K to 13K, and C11 and C15 from 47pF to 100pF.

Wiring-wise, as far as I can tell, I want to grab the Left Buss and Right Buss signal off the ribbon cable at the Submaster PCB.  This will be after the console's 22k summing resistors, but before the master sections insert driver, insert, fader, and fader driver.  Is there a best technique for patching in to a ribbon cable?  Or is it better to get it from the PCB somewhere?

I still want to use the other features of the master section like Control Room, Studio and Headphone outs.  I assume this is where the Mult out on the Booster section comes in to play?

Is the best practice to wire ACA-BO Booster Main outs directly to the LR output jack, and wire Booster Mult outs back to LR circuit after the now-bypassed Topaz fader amp?

Additionally, what are common applications for the ACA stage Mult Outs, if any?

Thanks for your time.

Graham

Possibly a stupid question but one I thought I’d ask before proceeding...

The + and - sides of both the ACA and Booster outputs are shorting together, is this a bad sign?

I’ve got my board stuffed and installed in a Soundcraft 200b and noticed this as I begun wiring it in.
Currently all I have wired is the Booster to Main output XLR connections.

It’s shorting with and without DOAs installed.

Thanks

lachlan.vercoe said:

The + and - sides of both the ACA and Booster outputs are shorting together, is this a bad sign?

It’s shorting with and without DOAs installed.

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These output pads have no connection at all when the PCB is unloaded. What you are measuring is the DCR of the output transformers that you have installed. It is likely not a direct short but a very low resistance. This is normal and expected.

Hey Jeff,
Thanks for the reply.
To be more specific I was using a continuity (Buzz) test on my DMM and getting straight continuity between the + and - pads for each output (though not say between the main and mult outs).

My PCB is loaded, power is hooked up and reading as it should on the DOA sockets, the only off board wiring I put in before seeing this was the Booster our to 200b Main XLRs...

lachlan.vercoe said:

Hey Jeff,
Thanks for the reply.
To be more specific I was using a continuity (Buzz) test on my DMM and getting straight continuity between the + and - pads for each output (though not say between the main and mult outs).

My board is stuffed...

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Yes I get that. The only component that will alter that reading will be the output transformers, nothing else. A continuity "beep" on a DMM usually sounds off well above 0Ω. If you want to check for sure, set your meter to read DCR and below 200Ω if its a manual range type.

Ah ok, great. Thanks Jeff!

Shouldn't the fader be 1K if using 48K isolation resistors and 2025 DOA? Working from memory so might be wrong.

Try this: Buy a cheap audio signal injector and inject audio tone from outside most circuit inward toward the DOA. When you lose signal or its severely degraded, the problem is mostly likely the section just in front of signal lost.

Billy

I have successfully installed this into my Soundcraft 200b.
All's working well and strewth it sounds incredible, such a step up from the 200bs master section.
It's got such clarity and heft to it!

On strange thing I have going on is that there are several points in the travel of my master faders where the signal jumps suddenly and then settles back quite quickly. Not unworkable in general but odd.

Any pointers as to what would be causing these sudden spikes?

Thanks.

lachlan.vercoe said:

I have successfully installed this into my Soundcraft 200b.
All's working well and strewth it sounds incredible, such a step up from the 200bs master section.
It's got such clarity and heft to it!

On strange thing I have going on is that there are several points in the travel of my master faders where the signal jumps suddenly and then settles back quite quickly. Not unworkable in general but odd.

Any pointers as to what would be causing these sudden spikes?

Thanks.

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Must be incorrect wiring of the fader. What op amps are you using?

Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).

lachlan.vercoe said:

Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).

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I think I had the same problem. Measure the faders to make sure which lead ist the whiper. Intuition may be misleading.

Are these GAR1731? Which op amps did you put on the summing section and which on the buffer? I'm still experimenting with mine...

lachlan.vercoe said:

Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).

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It could because this behavior is not at all normal.

Re. Opamps I can't remember which way around they are now, I've swapped the positions once or twice and have a bunch of others I'll perhaps swap in and out... Yes they are the GAR1731 kits, pretty sure I've now ordered several of all of the available DOA's from CAPI to try out.

I'll investigate the fader wiring, I'd kind've thought if it was wired incorrectly it'd be a Working or Not Working deal. Not so much this strange issue.
I did get a bit of guidance from this thread: https://groupdiy.com/index.php?topic=54847.0
The OP in that mentions a similar issue though no resolution is offered.
All this being said it's not an unworkable situation, just a few VERY narrow spikes to pass over before settling into a usable level for mixing.
And again Jeff, killer project you've offered! Really improves things!