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

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31cc7

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If I turn the mixer on, channels 2, 4, 6 are almost dead silent. Only when I overdrive them hard, they "pop up" and work fine when I turn the signal down. When I stop sending them music for a couple of minutes they "die" again and I have to overdrive them to make them work again.

So the 3 boards out of 4 have this issue and all three on the same right channel. That feels like maybe something to do with capacitors? As if the audio signal is low these can't get charged enough and the overdrive "jump starts" the circuit?

Could this be some sort of damage I caused by powering it with weak PSU in the beginning?

Other than that everything works great.

 

jsteiger

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31cc7 said:
If I turn the mixer on, channels 2, 4, 6 are almost dead silent. Only when I overdrive them hard, they "pop up" and work fine when I turn the signal down. When I stop sending them music for a couple of minutes they "die" again and I have to overdrive them to make them work again.

So the 3 boards out of 4 have this issue and all three on the same right channel. That feels like maybe something to do with capacitors? As if the audio signal is low these can't get charged enough and the overdrive "jump starts" the circuit?

Could this be some sort of damage I caused by powering it with weak PSU in the beginning?

Other than that everything works great.
To me this sounds like the classic symptoms of cold solder joints.
 

madbeavis

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I was able to isolate my issues:

" I am having an issue that I cant seem to pin down with the talkback/mute circuit on the BO side.  On power up I can pass audio for about 30 seconds after which the mute becomes engaged. I can short the G and S pins of the J111 and it will start passing audio for another 30 seconds before repeating the same behavior."

I was using a regulated bench DC supply set to +-16 @ 1A  which was cutting out after 30 seconds. I wired up a 500 rack supply and everything works fine. I am unsure what is wrong with my test supplies but I ordered a SMPS to get around this.

Thanks for your help everyone!
 

31cc7

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jsteiger said:
To me this sounds like the classic symptoms of cold solder joints.

Thanks for this hint! I pulled it out from the rack and removed one 2S-LA module that had problem. I inspected the solder joints and all looked alright, however, I noticed that one DOA was barely in. So I pushed all in again. The problem is that the connections feel a bit loose.
To confirm the issue I put it back in the rack and now all channels work except 7 (which was working fine before I pulled it out).

It looks like the connections between op amps and the boards are too loose  :(

I am using Mill-Max pins and sockets as in the BOM.

I need to figure out how to make it fit tight.

Before inserting the DOAs I loosened the socket by inserting a single pin into each.

edit: removed it from the rack, wiggled the DOAs a bit. Shouldn't have touched the 5 and 6... I racked it back and now 6 doesn't work, but 7 is okay  :D
 

jsteiger

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31cc7 said:
Thanks for this hint! I pulled it out from the rack and removed one 2S-LA module that had problem. I inspected the solder joints and all looked alright, however, I noticed that one DOA was barely in. So I pushed all in again. The problem is that the connections feel a bit loose.
To confirm the issue I put it back in the rack and now all channels work except 7 (which was working fine before I pulled it out).

It looks like the connections between op amps and the boards are too loose  :(

I am using Mill-Max pins and sockets as in the BOM.

I need to figure out how to make it fit tight.

Before inserting the DOAs I loosened the socket by inserting a single pin into each.
The opamps cannot be fully seated then. They should NEVER fall out or be loose with the proper pins and sockets that we use. We've had 40 VP28's (80 opamps) on the road recording Chris Stapleton shows for 2 years now and never had one problem...knock on wood (my head!).

Have you seen this? https://capi-gear.com/catalog/DOA_Install.php
 

31cc7

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Ok I saw this, but I am not sure why I didn't register "You definitely want to make sure that the paperclip is a little smaller in diameter than the DOA pin"  ::) I didn't have a paper clip around so I used the DOA pin to loosed up the sockets. I guess I loosened it too much. My thinking was that if the DOA goes in with the same pins, then it shouldn't be too bad... wrong.

I reinserted the op amps and now everything is working. Finally  8)

Thank you for all the help! I will try to use it on my next project and hopefully all is going to go well.
 

jsteiger

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31cc7 said:
Ok I saw this, but I am not sure why I didn't register "You definitely want to make sure that the paperclip is a little smaller in diameter than the DOA pin"  ::) I didn't have a paper clip around so I used the DOA pin to loosed up the sockets. I guess I loosened it too much. My thinking was that if the DOA goes in with the same pins, then it shouldn't be too bad... wrong.

I reinserted the op amps and now everything is working. Finally  8)

Thank you for all the help! I will try to use it on my next project and hopefully all is going to go well.
Nothing wrong with using a DOA pin. I don't think you would ruin or overly loosen the sockets. I've got test jigs with sockets that have been used many hundreds of times and they all still work great.
 

31cc7

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I am extremely happy with this summing mixer, but after a week in the rack I lost one channel. The op amp? Well, I tapped it from the sides a bit and channel came back. It seems like op amp lost contact again. There is def something wrong with these Mill-Max sockets / pins :(
 

jsteiger

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31cc7 said:
I am extremely happy with this summing mixer, but after a week in the rack I lost one channel. The op amp? Well, I tapped it from the sides a bit and channel came back. It seems like op amp lost contact again. There is def something wrong with these Mill-Max sockets / pins :(
If those are the pins/sockets from my store then they are solid. Maybe there's something else up...
 

31cc7

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I got them from Mouser. If I get some more spare time I'll take a look inside again. Most of these op amps are a bit loose in their sockets.
 

jsteiger

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31cc7 said:
I got them from Mouser. If I get some more spare time I'll take a look inside again. Most of these op amps are a bit loose in their sockets.
The pins should be .04" diameter and the sockets should have a range of accepting .032" to .046" pins.
 

JW

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In the Yamaha PM2000 console, there is a summing section of two IC's then a send and a return to the fader with a booster amp (DOA) like with API.

I'm wondering if I can bypass my console's summing IC's and simply insert the first half of the ACA circuit up until the fader and then come back into my master channels at the fader (10K)

 

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JW

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Thanks Paul.

I guess my specific concern is I have 10K faders prior to my discrete output stage in the PM2K. If I'm plugging back into the PM2000's faders, will that present a load for the ACA (no 325 booster)  circuit that it's not expecting? Because from memory I'm remembering a 1K fader used normally between the ACA and the output booster.

Also, do I even need the interstage transformer? I understand the ACA inserts a -6dB  drop that the interstage transformer and the 325 card make up for. I assume the DOA output stage in the PM2K could do the same? (990's in my case) It is feeding 1:1 600 ohm transformers though so no 1:2 on the way out.

AND, I'd have to adjust the feedback on the ACA for unity gain AND flip the polarity one more time on the PM2K output transformer I believe. But other than that I should be golden?

It seems cool because it looks like a possible mod I can do locally in the master channels and for relatively inexpensively as it uses the existing output transformers and output DOA's of the PM2K. And get rid of those two IC chips in the main L/R signal path.

By the way, for readers, it's not clear because of my zooming a couple posts back which IC's are the chips and which is discrete on the PM2000 schematic. IC1 and IC2 are the Hitachi chips and IC4 is the discrete booster stage.
 

Potato Cakes

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I think you're making it a little too complicated. If you're wanting the characteristics that the ACA-Bo imparts, then it should be used in its entirety, bypassing any additional active circuitry in the console that follows the stereo/master summing network.

So console summing network - ACA first stage - fader (just the fader) - ACA booster input - XLR output. The description says you can use up to 10k for faders, which is what I am using.

You then would figure out where you want to take a pickoff point for monitoring, etc, if that is what you would need. If you want to use the other IC in the summing path or fader makeup then maybe you just need a line amp card of some sort to affect the sound to your tastes.

Thanks!

Paul
 

JW

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I breadboarded the ACA circuit yesterday. I found the parts around so decided to try it with my Yamaha's booster amp. Hmmmm. I'm getting the sound of a bad opamp (crackles pops) and no (audio signal)

Question, what is the shield at the very beginning of the ACA ostensibly connected to? The input channels'  0V signal ground reference?  Or floating?

For the output of the ACA: To be clear, I'm sending the negative leg of the ACA output cap (C16 in Jeff's schematic) to the top of my Yamaha's 10K fader, without the 2623 transformer (the DOA output of the PM2K schematic is below)

Wondering if my lack of interstage transformer is the issue or something to do with using a noninverting opamp right after an inverting one? (With the intention of final polarity being established at the 1:1 output transformer)

(I know I know I should just rock the full circuit. My reasons for doing this are sort of boring and embarrassing at the same time. So skip if you don't want to read blah blah's. Essentially I've already done a full ACA+325 booster install, liked the sound but ran out of headroom because of not enough final gain. This could have been remedied by adjusting the feedback resistors in the aca, but at the time I didn't understand that that is how you set gain for the opamp. I could have simply wired in pots and set unity gain. Instead I ripped it out and sold it, went back to my stock master channels. I'll probably go back to Jeff's full kit again, but in the mean time, and broke time, this seems like a cheap way to upgrade the PM2K master busses, keep it in the channels, and even perhaps relegate these to the peripheral busses if/when I go full ACA once again.)
 

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eternal slang

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Hi Jeff,

Thanks for making these boards available!

I would like to try it in the mix bus section of a Chilton QM3 and would benefit from some guidance on how to implement it, see schematic.

Any mod I would need to do or I can just disconnect the i/o pins before/after the remix output amp and reconnect it to the ACA-BO?
Will it handle 24vdc if I use the console rail supply?

Thanks for your help  :)

Fabien
 

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jsteiger

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eternal slang said:
Hi Jeff,

Thanks for making these boards available!

I would like to try it in the mix bus section of a Chilton QM3 and would benefit from some guidance on how to implement it, see schematic.

Any mod I would need to do or I can just disconnect the i/o pins before/after the remix output amp and reconnect it to the ACA-BO?
Will it handle 24vdc if I use the console rail supply?

Thanks for your help  :)

Fabien
I don't think you need any mod's. Looks like 15k bus R's so you'll need to modify the feedback R and C on the ACA portion of the 2-ACA-Bo. I'm pretty sure that info can be found by scrolling backwards in this thread.

The 2-ACA-Bo card will handle 24V rails no problem but make sure your PSU decoupling caps are 35V or higher. Also make sure whatever discrete amps you use can run on 24V rails. A 2520 or 1731 cannot.
 

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