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

[jsteiger]

What fader is it and how do you have it wired?

 

[lachlan.vercoe]

I'll have to double check after work, fairly certain the 200b is 10k faders all round. 22k bus resistors.
And as for wiring I replicated it from pictures from the below 200b/CAPI thread.

https://groupdiy.com/index.php?topic=54847.0

 

[jsteiger]

I'll have to double check after work, fairly certain the 200b is 10k faders all round. 22k bus resistors.
And as for wiring I replicated it from pictures from the below 200b/CAPI thread.

https://groupdiy.com/index.php?topic=54847.0

Looks like he was having the same issue...

 

[punk]

installed, finally, into a soundworkshop SW34. very easy mod and sounds great.
thanks Jeff!!
byron

 

[a_wachtmann]

Hello,
I want to upgrade my D&R 8000's master section with the ACA Booster and stumbled upon two questions.
The master bus on the 8000 is fed through 12k resistors (see first picture). Can I put a 35k resitor in front of the ACA input to get to 47k ? Or how do I recalculate the feedback resistors and caps on the ACA?

And can you give me some tips where I should bypass the original master section? My first thought was to go from the master bus and return before the insert point (see second picture). But then I would loose the monitor bus. And I would like to keep the original insert point. Where would you set the bypass points?

thank you
Arne

 

[boji]

Would someone mind explaining how values are decided on cap bypass resistors that go to primaries on the tx's in the CAPI aca bo? 

for the 2623 side, it is 100r.  For the boost side, the 2503 has a 47r at 1%.  I assume these values are critical?

I ask because in this case, I only need the first stage on the ACA side (28k nfb) for outputs,  but I have paired it to a 2503 instead of a 2623.
Would it be ok to use the 100r on the 2503?

Thanks in advance for any help!
-Boji

 

[Math5461]

Hey Jeff and 2-ACA users,

I am building a 16 channel summing mixer.  Each channel inputs to Jeff's 2S-LA cards (http://capi-gear.com/catalog/product_info.php?cPath=22_191&products_id=438),  P&G 10k faders, and Pan Pots (or switches) feeding the 2-ACA.

I am hoping to have VU's on the master bus using this buffer: https://www.jlmaudio.com/shop/vu-buffer-kit.html?display_tax_prices=1

I'd like to use Jeff's Floor Box Power Supply:  http://capi-gear.com/catalog/product_info.php?cPath=176_178&products_id=358


Does anyone have a simple schematic or wiring diagram I can follow to achieve this?

Thanks for any help y'all can give!

-Josh

 

[Potato Cakes]

Just wanted to double check one thing before I install this in a TAC Scorpion. All of the shield and DC ground connections are all tied together on the ACA-Bo except at the ACA input where those shield connections are isolated and go to the ACA DOA. Since these connections will be all inside the console and no separate shield or (-) connection on the master channel, do I just tie these connections to the 0V (ground) connection as well?

Thanks!

Paul

EDIT: The answer is yes.

 

[MrBlomski]

I want to use the 2503-L on the 2 ACA.

Do I have to follow this wiring, according of the cape datasheet?

To use the 2503-L in place of the EA2503, follow this table:
2503-L        EA2503
Red              Gray
Pink              Blue
Yellow        Yellow
Orange      Red
Black            Violet
Gray            Green
White          Orange
Violet          Brown

Cause I hear a tiny bid of audio after the booster side.
thanks.

 

[TubeMonkey]

Hey Jeff and 2-ACA users,

I am building a 16 channel summing mixer.  Each channel inputs to Jeff's 2S-LA cards (http://capi-gear.com/catalog/product_info.php?cPath=22_191&products_id=438),  P&G 10k faders, and Pan Pots (or switches) feeding the 2-ACA.

I am hoping to have VU's on the master bus using this buffer: https://www.jlmaudio.com/shop/vu-buffer-kit.html?display_tax_prices=1

I'd like to use Jeff's Floor Box Power Supply:  http://capi-gear.com/catalog/product_info.php?cPath=176_178&products_id=358


Does anyone have a simple schematic or wiring diagram I can follow to achieve this?

Thanks for any help y'all can give!

-Josh

If you use the 2ACA board instead of the 2S-LA you could rewire the output configuration to give you 1:1(*3) Then use one of the taps to feed the output, and one to feed the VU meter. You could probably get away with making back up the 6db loss from switching from 1:2 by adjusting the value of the feedback resistor.  I need to check in my desk but i'm pretty sure the vintage API's all used this exact configuration to drive the meters without causing signal-path distortion from running it in parallel.

This configuration would also give you an insert/600 fader between the summing stage and the line amp stage.

 

[jvancorduroy]

I am looking to replace the quad master section of my Auditronics Son of 36 Grand console . I would love to replace this with just a stereo master buss with these CAPI  2 ACA . Is this achievable on this console with these  ? Any guidance on how I should proceed would be greatly appreciated .
Dave

 

[Potato Cakes]

I am looking to replace the quad master section of my Auditronics Son of 36 Grand console . I would love to replace this with just a stereo master buss with these CAPI  2 ACA . Is this achievable on this console with these  ? Any guidance on how I should proceed would be greatly appreciated .
Dave

You would need to find the schematic of your console then locate the where signal goes to the L/R summing buss. Essentially you would break that connection and go into the ACA-Bo. You then have to determine how you want to wire the master fader (back and forth to the master channel or directly wired to the fader). You can then go directly from the outputs of ACA-Bo to the physical console outputs or back to the master section again for routing and monitoring. Doing this will unbalance the signal again.

Be advised, you should possess pretty good soldering, schematic, and troubleshooting skills before undertaking this project. It's not a terribly difficult procedure, but if you are somewhat new to the solder jockey arena (and you may not be) this could potentially become an incredibly frustrating and unexpectedly expensive endeavor. However, upon a successful complete, you be glad you did. It's a great (subjective) improvement if you are unhappy with the sound of your console's mix buss.

Thanks!

Paul

 

[jvancorduroy]

Thanks  Paul.
I do have all the original schematics so that  is a bonus .
The Master and Monitor section also need an overhaul  so I will probably look for someone to undertake that work for me to retrofit this into the  console .
Cheers
Dave

 

[31cc7]

I am sorry if this is a stupid question, this is my first project of this kind.

I am building a summing mixer using 2S-LA into 2-ACA-Bo. Everything seems to be working and now I am at the stage of putting it together in the case and calibrating. I did CMRR for 2S-LA modules and now I need to set the levels.
I don't want to have any faders / potentiometers and I assembled those modules to support 1k fader. For that I would put 1kOhm resistor across the output of given stage.
Now, how do I adjust the trimmers?

Should the goal be that if I send 1kHz 0.775V sine wave to input 1 I should read back 1kHz 0.775V sine wave from the output of the mixer?

Since the "faders" are set, I should just adjust the trimmer of 2S-LA second stage until I get the right signal from 2-ACA-Bo?

Should the value of "master fader" at 2-ACA-Bo be lower than 1kOhm to be at 0?

 

[31cc7]

So I decided to just wire this up and measure what happens. In place of faders I put 1kOhm resistors.

I run sine wave from my DAW @ -18 dBFs and that goes through 2S-LA (with 1kOhm "fader") to EA2623-1 transformer wired 1:2 through 47kOhm resistor to 2-ACA-Bo. The main output gives me nice sine wave peaking at 9.20V. I understand that is about 18dB gain? That would about match what I read in the documents. Sweet.

Now, where do I turn it down to get unity?

My instinct tells me to replace 1kOhm resistor with a potentiometer in 2S-LA, turn it down until I get unity, measure and replace with resistor?

 

[jsteiger]

Now, where do I turn it down to get unity?

My instinct tells me to replace 1kOhm resistor with a potentiometer in 2S-LA, turn it down until I get unity, measure and replace with resistor?

Yes you will need a voltage divider (2 resistors). The first will be in series and then immediately following is an R shunt to ground. The total of the 2 R's will be 1k, give or take. You can wire in a 1k trimmer, set it where you want then take it out to measure the values.

 

[31cc7]

Yes you will need a voltage divider (2 resistors). The first will be in series and then immediately following is an R shunt to ground. The total of the 2 R's will be 1k, give or take. You can wire in a 1k trimmer, set it where you want then take it out to measure the values.

Oh yes! Thank you for pointing that out.

 

[31cc7]

After measuring the potentiometer I found that the ratio about 160Ohm / 840 Ohm gave me a 1V peak. After a search through my box of resistors I found a pair 180Ohm / 820Ohm, so that's what I am going to install.
This is exciting. Looks like I am very close to getting my summing mixer done

 

[31cc7]

Good and bad news.

My summing mixer has 8 channels. I measured each channel against channel 1 with an oscilloscope. Everything looked perfect.
So I put the case together and off to rack it goes.
I connected it to my audio interface, set up outputs in Ableton and I hear nothing - good sign.
Now I played some random sounds through each input and I barely could hear anything. I had to set gain up to 24dB in Ableton to hear anything. Some pairs only had only right channel coming or there was imbalance. Last 7/8 sounded leveled but thin.
That's fairly different from what I observed via oscilloscope.
Then when I disconnected my power supply I heard loud sound something like a siren wailing for a second from the power supply and the case of the PSU was very hot.
Now I think that my PSU is too weak. I have used a PSU with transformer rated 25VA with LM317 / 337 set to -16V/16V. It is "off the shelf" Chinese PSU I put in my own case.

In this mixer I have 20 DOA and 12 transformers.  My napkin calculations made me think I should be just about okay.

I hope I didn't damage anything :-(

I am going to look for beefier PSU. Is there something you could recommend?

edit:

I have ordered a bigger transformer, as the one in the PSU doesn't look "powerful". I will replace the transformer and if that won't help I also ordered LM333T and LM350T to replace LM317 and LM337 and will maybe tweak other components of the PSU.

edit:

I connected this through a patchbay I have never used before as I realised I don't have right DB25 cable. Anyway as I didn't want to reconnect everything I just bypassed 1/2 summing channels to my buss and got the same "weak" sound as I had on channels 7/8 of the mixer. That got my pressure running as I thought "great I fried my equipment".  I bypassed the patchbay and sound is back to normal.  So I am hopeful that stronger PSU will bring my mixer to life. I am also waiting for correct DB25 cable.

 

[31cc7]

Today I got time to rebuild the PSU as I received all the parts throughout the week. This time I used 50VA dual 18V transformer.

I reviewed the insides with fresh eyes and everything looked okay. I plugged the PSU in. No smoke - so far so good. Turned it off and connected with DB25 to my audio interface and the outputs to another and turned back on.
I created simple project with Ableton to check each channel. Turned play and...
Everything works! Every single channel passes audio and the sound is incredible.
But... it is all extremely quiet. I had to give like 30dB gain in Ableton to hear anything.
I am not sure what could be the issue. I would suspect the resistor dividers connected other way around on all channels? Problem with cables?
Looks like I need to get it on my desk and check with oscilloscope what's going on.
This is exciting as I am getting close. I am also waiting for the meter drivers, hopefully by the time I solve this I will receive these.

I have attached a picture of the summing mixer I took today: