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

[jsteiger]

Paul

You can "split" your vocal signal by running it thru two bus R's. This will not change the stereo spread of your console outs, which should also be sent thru bus R's.

You should be able to just unbalance by tying the "-" to ground. It may need to float though depending on the preceding device. You will have to try it and see what works best.

As for caps, just make sure the PSU decoupling caps are rated higher than your supply voltage. The rest should see very little DC unless and opamp takes a sh!t.

 

[Potato Cakes]

Jeff,

So I got everything put together and started to do some testing. Nothing is mounted in a case yet. At first, I was getting a buzz but found that when I picked up the transformers and moved them about the buzzing went away, so I think that when I get it mounted in a case and the body of the transformer is in contact with the chassis ground that will resolve that issue. The last thing I have to sort is the fact that the audio is band passed. I ran pink noise through it and it comes back out the other end at about -20dBFS lower from what is being sent out and it's band passed with the center around 2kHz. I thought I had brought a couple of DOAs to do testing, but I apparently I only one out here, so I won't have any way to make see if that is the problem, but at this point I suspect it is.

Before I resign to that conclusion, I wanted to double check a couple of things to make sure it's not something else. The electrolytic caps that I used were a slightly higher voltage than what was on the BOM. The red lead on the EA2622's is tied to the 0V on the PSU as is the shield on the outputs. I wired the transformer in series to make it 1:2.

My plan was to get this up and running while I'm out and then slap it in a case when I get home on Monday before I send it off the monitor guy for final testing. If it is the DOA then I'll just have to wait. I moved the one DOA I have to the other side and I had the same problem, but both sides of the PCB I am using are wired the same, so I couldn't just automatically blame it on a faulty op amp. So if you or anyone else thinks anything is suspect besides the DOA, please let me know. I will be double checking component placement in the meantime.

Thanks for your help, and thanks for your amazing products!

Paul

 

[Potato Cakes]

Also, I'm using 47k resistors for each of the "+" inputs being summed together as is shown on the diagram on the website. All voltages at the DOA sockets seem to match what I'm getting at the PSU.

Thanks again!

Paul

 

[Potato Cakes]

Correction, it is the EA2623-1 transformer and not the 2622.

Paul

 

[jsteiger]

It sounds like a ground problem somewhere. Depending on the device that is feeding the 47k R's, you may need to either float the "-" or ground it.

 

[Potato Cakes]

It's finished!

It was the unnecessary 47k resistors on the outputs that were causing the transformer to be unhappy. Hilarious! Once again, as Jeff so eloquently said, it was the simple things.

First, thank you Jeff so very much for answering my questions and emails. And for making such sweet products.

It's a 3 to 2 summing mixer that has one mono and one stereo pair that feeds two stereo outputs, one that goes directly to the artist's IEM transmitter and one back to the console so the monitor guy can cue what the artist is hearing. As I mentioned before this is to keep the star vocal chain completely analog to the IEMs to mitigate effects of latency to one's self in a vocal mic from digital consoles. I'm using a pair of 8035 meters from Mike at Hairball and I used the MNATs power supply that I was going to use for my stereo 1176, but wound up just building out both power supplies on the main PCBs. And I didn't have another power supply at the time. Also, the MNATS power supply is super handy as it has two LED power points, which I used for the VU meter lights and the power switch light. I got the chassis off of eBay. One day I'll figure out how to do the sweet custom panels like others on here, but I was happy that I was able to cut rectangular holes without completely disfiguring the case. And this projects was time sensitive, so having a panel made was not an option. Maybe next time. Currently I have Pier's APP992 op amps inside. Maybe after this upcoming tour I'll get to try different DOAs to be more aware of the sonic possibilities. I used capacitors that with higher voltage than on the BOM to give me the option to run it on higher rails that +/-16V. Currently running it at 18V. The APP992 are rated up to 24V. 

It is super clean an quiet. I'm very happy how it turned out. We start rehearsals next week so I'll find out then if it really makes the improvement I'm hoping it does.

Again, many, many thanks to Jeff for lending me his time and expertise in helping me on this one. The next time you're in Nashville and I'm home the drinks are on me.

Thanks!

Paul

 

[Potato Cakes]

One more pic.

 

[Potato Cakes]

One more thing I should mention about these boards is that they are very well made and the solder pads are very durable. I built the circuit board and did all the testing and trouble shooting with no chassis while on tour. I soldered and unsoldered the same sections many times while back stage between set changes. Sometimes I had to hurry up and thrown all the parts and tools in the same box when I ran out of time before load out started. Other PCBs I've built up the solder pads at the very least would have come off.

I already have another monitor guy who wants me to build something similar to this to replace the small side car he is using to do the very thing this box is intended to do. Hopefully later this year I can build one for my studio and see how it holds up to my Mixdream XP. I'd love to build a small console using these boards, but I am not great and do not enjoy the metal work part of DIY.

Anyway, this is a sweet project and I can't wait to build other summing boxes with these boards.

Thanks!

Paul

 

[kante1603]

Well done Paul!
Since I'm a "live guy" too I love things that help me in my work,and doing these on my own always makes me very happy (....jealous people asking "....what is that?" on tour  ;D ).
Plus it has a great learning effect and makes it serviceable.
Jeff's kits are top notch,no doubt,I have quite a few from them,and I use them live same as in the studio.....I mean all of them!
And for doing frontpanels,may I suggest to try fpd?It is really easy,once started you'll get infected,promised.
E.g your panel would take me less than five minutes or so.The software runs on all systems and is for free.


Have fun,


Udo.

 

[JW]

Hello Jeff or anyone else,

I wonder if you guys could help me here. I've been operating with about 20 channels summed through the ACA buss for awhile now and it's been great. But now I want to add my console's 6 remaining busses to the ACA summing as well. I'm attaching a schematic of my Yamaha PM2000 master buss module.

Basically, I want to go straight out of the program buss at the point where it says "To Matrix Post."

As you can see at the bottom left side of the schematic, where it says "From PGM out," each of these PM2K master buss modules receives routing from every other buss module into it's "matrix" There is a 10K pot followed by a 33K resistor here.  The ACA summing buss has the right capacitors for 33K summing resistors because that's what the input strips use too.

So, can I just tap the signal after the 33K resistors at points 7 and 8 (where it says "From PGM out") and insert that into the ACA 2 buss? I won't be using the "matrix" part anymore because the ACA takes it's place.

Also, I'm pretty sure I don't need a booster board but I thought I'd ask. When I get all 32 channels up and running plus 6 busses, is that gonna be okay for the ACA, or will I need another booster board?

 

[jsteiger]

Yes this sounds like the way to go. You should not need any other boards.

 

[XAXAU]

Hi guys! I wanna build a 2-aca-bo box and sum my ITB mixes plus track synths through it.

1. Would I need the new line cards to make it handle synths? When I track my Apogee Duet 2 chooses the "line" option and not hi-z (don't know the output impedance of the synths).

2. I want to get some of the console vibe as well so I'm thinking if I go with the line cards will I still be able to inject the outputs from my Motu 828Mk3 into them?

3. Is it possible to use a 2623-1  after the first stage of the 2s-la and unbalance it and do the same after the 2nd stage? This is just to put more iron in the signal path for mojo. It would be great if the signal going into the 2-aca-bo was at unity but I have no clue if it is? The transformers would have to be wired 1:1 since the first stage is -6 and the second is +6?

4. The input of the 2s-la seems to be balanced so maybe it won't be able to handle an unbalanced synth?

5. Is CMRR calibration needed for the 2-aca-bo?

I'm grateful for any help as I'm a newbie!

 

[Gwen]

Hi guys,

I'm kind of a newbie in this DIY world, and most of all, i'm not so familiar with all this technical langage,
Sorry for any missunderstanding, i also looked for answers earlier in this thread without success...

Like JW, i own a PM2000, but unlike him, i don't want to use the amplifier board in place of the Matrix Output, but i would like to use it in place of a stereo program output, to get a different 2buss from the others 6 pgm outs.

Every input channel is feeding the pgm bus bar with 33K resistors,
Can I use the 2_ACA_BO in place of the pgm 7&8 circuitry, keeping only the master fader ?

If we look at the PM2000 schematics JW forwarded above ( July 06) I imagined (i may be naive) using the signal coming from points 1, before IC1, through the 2_ACA inputs,
Do the 33K resitors make a problem ?
Do i have to use the Booster and how ?

Thanks for any help

Gwen

 

[coldwar]

just a quick question about the fet mute control.  what pins should i ground and should i just ground it to the ground of the fet?

 

[jsteiger]

just a quick question about the fet mute control.  what pins should i ground and should i just ground it to the ground of the fet?

There is a special note in the build tips doc as well as on the skizo http://capi-gear.com/catalog/support_docs.php#ACA

 

[coldwar]

It all makes sense! I was thinking about stuff in a way that made things more difficult.

Got everything up and running! My only problem is the right side has considerably less output on the booster side. Swapped stuff around running the left from the right and etc....  Seems like the right side is the culprit. Any ideas?

 

[jsteiger]

Check/swap opamps and then look for cold solder joints on the board. There is not much to the circuit so it should be easy to hunt down.

 

[coldwar]

gotcha!  already swapped opamps same result looks like we will be checking of those cold joints.

 

[jsteiger]

Did you swap your "insert" or fader wiring between channels?

 

[coldwar]

both channels work on the "working" side.  so both the left and right channels work on the left side of the booster section.  if that is the question?