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

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Well, you can experiment a little but for the typical usage as far as my ACA cards are concerned, you will not use any R's other than 47k. Those 10k's will all be 47k. I also think you will find that unbalancing the signal at the output of the sound card is the way to go.
 
Oh ok, it sounds much clearer to me this way, thank you.

I still need to figure out how to wire a nice pair of VU meters.

Does the booster section of your module as a constant gain in order to adjust the output with the master fader? Or is there another way of doing this? Since I want to rackmount the whole thing I wanted to have a rotary switch and a fine trim, or just a level that you adjust with a screwdriver from time to time thru the front plate
 
thomasdf said:
Oh ok, it sounds much clearer to me this way, thank you.

I still need to figure out how to wire a nice pair of VU meters.

Does the booster section of your module as a constant gain in order to adjust the output with the master fader? Or is there another way of doing this? Since I want to rackmount the whole thing I wanted to have a rotary switch and a fine trim, or just a level that you adjust with a screwdriver from time to time thru the front plate
Click to expand...
Hi Thomas,

having a master fader or pot is highly recommended,otherwise you can't really keep control over your summed signals.
About metering,I guess you will meter the mixer output,right?
Do you already have vu meters you want to use?
In any case you'll need rectification for them.Sometimes it is done by diodes,sometimes electronic using a tl071 as a buffer and fullwave rectifier.These are normally high impedance circuits,mostly having 100k or more ohms.So the rest or better the part previous to it will not "see" them as a load.
You can strap them directly over your xlr pins 2&3 or the mult on the booster output ( which is the same electronically but better to reach on the molex connector).
And remember you have an unused secondary output on the aca booster board that might be usefull too.

Hope to have helped,

Udo.
 
Thanks Udo for your advices, but I am still a bit lost here.

When mixing on a large desk like the 4K at the studio, the master fader is always all the way up except when I am doing fades or when the console output is going in let's say a comp that I wanna push more or less depending if it's a chorus etc

I understand the need of a master fader or master pot in my summing device, but my guess is that it will be all the way up 97% of the time... Anyway, you are probably right.

Can anyone recommend a good stereo pot?

As far as the VU meters are concerned, do you think this might do it? http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=19

Thanks again, and sorry if I seem to ask dumb questions  :p
 
Hi Thomas,

there are no dumb questions,just dumb answers ;)

Concerning the buffer amp for your vu meters,yes,that's how I did it a lot of times.Joe's pcbs are so small that you even can solder them directly to the back of the vu.

The pot question is more a matter of money since you want the both tracks to match as close as possible.
If it was a fader then I would go for P&G,Jeff sells them in his store.
For a pot there are a lot of them to find everywhere,just look at the specs-especially for tracking- and the money you can spend.Don't use cheap ones because you'll have nothing but a horrortrip listening to pan positions while moving it.I would look for bourns or p&g again.Collin at AML carries a good collection.Conductive plastic prefered over carbon types of course.Even Alps has one with pretty good specs concerning tracking,it's the "blue" series pot.Do a search on google or visit some of the well known pages.

And I don't comment on having a master fader fully up from start,you wouldn't like it ;D

Cheers,

Udo.
 
This was not a good example because the 4K has a VCA based master fader, but you see my point anyway :)

I am going to use those Vu meter cards, they seem appropriate. Thanks for the tips about the blues pots and plastic conductive ones, I am going to score one of those these days and start building.

Do you think that if I buy and use 2 unbalancing transformers right before the ACA module it will be better that unbalancing all with a simple cable?
 
thomasdf said:
Do you think that if I buy and use 2 unbalancing transformers right before the ACA module it will be better that unbalancing all with a simple cable?
Click to expand...
Most likely yes but I would try it on a small scale before buying a bunch of iron.

The API fader nomenclature can be misleading. All of their old style faders were label "0" at the all the way up location. There is also a small dot that indicates the 12dB down point from full open. For all intents and purposes, this is unity gain so each fader has 12dB of gain in hand at the fader for all their applications. Funny enough, it is pretty common to have the program fader all the way up same with the subgroups. Maybe intentionally slamming all of these summing booster stages is one of the things we all enjoy about the old API sound. I say experiment and do what sounds best for your particular set up.
 
thomasdf said:
This was not a good example because the 4K has a VCA based master fader, but you see my point anyway :)
Click to expand...
aaaah,you meant an ssl 4k.Yes,that's o.k. on vca based consoles,same as on ours,pardon me!

thomasdf said:
I am going to use those Vu meter cards, they seem appropriate. Thanks for the tips about the blues pots and plastic conductive ones, I am going to score one of those these days and start building.
Click to expand...
Cool.
thomasdf said:
Do you think that if I buy and use 2 unbalancing transformers right before the ACA module it will be better that unbalancing all with a simple cable?
Click to expand...
Do you mean prior to the aca stage?
I wouldn't worry too much about it,your feeds are the outputs of an audio interface,no?So you're on a pretty high line level which normally means a good signal to noise aspect.If your cables aren't too long it should work unbalanced.

Cheers,

Udo.

Edit:Ooooops,double post,excuse me Jeff.
 
Another few questions haha
The module needs -16 / +16 power so I assume it is direct current, but I am having a hard time finding a 220V > 16V transformer...

That being said, I am starting to drill the rackmout box this week! I will keep you posted. I am going to make a prototype first, without vu meter in an beaten up rackmount that I have here. If everything is OK then I'll upgrade it to a "deluxe" version :)

I got the the thing about the 47K resistors, but what value should I choose for the "center" inputs resistors?
 
The typical way would be to route your center signals thru two 47k bus R's, one to left and one to right.

Joe from JLM has a few PSU kits that will work good for this. Yes you need DC.
 
Depends on how many opamps you have total. In this configuration they will draw around 25mA each. So 10 would be 250mA and so on. I would make sure you factor in some headroom room though. Most of the smaller size supplies that PPA, Owel and JLM have are capable of 800mA or so.
 
Hi folks. I am busy ith soldering these days, and drilling the box and etc... And I have to say I am quite pleased with what I am seeing right now. I think I will be able to test it in a day or so.
Anyway, I have a weird newbie question now... How should I wire the pot so it acts like the fader? Let's just consider one side for easier understanding:
The "Hi" lead is going to the 1st pin of the pot (from ACA) and is going from the middle pin to the Boost section.
The "Lo" lead is going to the third pin of the pot, and then from there to the Boost section.

I test this with my ohmeter and had weird result, am I doing something strange?
I am used to wire pots in guitars or various piece of gear but I am stuck on this one... I am sure this is no big deal and you guys can sort it out easily.

Thanks
Thomas
 
Ok, I figured out a way that seems to be working... Still waiting for the PSU regulator to get into my mailbox and then I'll be able to do some testing... I can't wait!
 
I finished mine today. I haven't done proper testing yet but I had a weird thing going on, a 280Hz hum that disapeared after a while... Scary because I need to find out where it's from but I can't since it's not here anymore...

My master "fader" pot is not wired properly because it is not efficient... Do you guys have a clue?
 
The usual problems folks have are ground related as a lot of times you have ones PSU for the console and one for the summing. I would experiment with different grounding schemes.
 
Hey guys!

I just bought an Allen and Heath System 8 MKI console and I was thinking about upgrading it.

I'm going to recapp it and upgrade some parts, and I thought I could possibly apply this board in it as well for better summing performance.

I'm not an expert in electronics, and I just recently discovered my passion for DIY but I think I could do it.

Could any one looking at the schematics could tell me if mounting this board would be possible?

You can find the schematics here: http://www.allen-heath.com/uk/Products/pages/DiscontinuedProductDetails.aspx?productId=System8

Any advice will be much appreciated!

Thanks
 

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