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

[martthie_08]

I'm not sure what you mean about the Molex connectors though? All the connectors are .156 Molex. Do you mean use all 3 pin instead of the 2 pin?

Jeff, thanks for clearing that up, I was so used to using the smaller .1 Molex stuff that I had completely forgotten that they have different pin spacings, hehe :

yes, I am now eager to finish the summing section, currently waiting for you to stock the EA 2623-4 again. I am also running out of 2520 so it will be interesting to see what you have coming up in DOA lands...

I am also thinking about having the insert after the summing balanced, knowing this was not the way it was done originally but my setup isn't really "original" either ;D

Thanks!!

 

[alexc]

Hi Jeff

Just wondering if you might have some info on connecting some channel input boards
(such as your mic pre), thru a big fader to your ACA board.

Looking to hookup a simple submixer here - no pan or switching or anything.

I'm not sure how to couple the traffo balanced output from a 312-style board to a reasonably
common 100m fader (2K?, 10K?) and whether an additional post-fader doa might be required.


Thanks
Alex

 

[jsteiger]

Hi Jeff

Just wondering if you might have some info on connecting some channel input boards
(such as your mic pre), thru a big fader to your ACA board.

Looking to hookup a simple submixer here - no pan or switching or anything.

I'm not sure how to couple the traffo balanced output from a 312-style board to a reasonably
common 100m fader (2K?, 10K?) and whether an additional post-fader doa might be required.


Thanks
Alex

Hi Alex,
Take a look at the reference docs page on my site. There is a basic sketch Brent gave me years ago. I had a simple 2 to mixer with 312's feeding 440 faders being summed thru the inverting inputs an a 325 card. Same exact principle you are after. The 440's were 600 ohm. 1K faders would work just fine. You could probably even try other fader values if you have those on hand. The output of the preamps is being unbalanced but no biggie. This is essentially how the insert return is on my input channels, unbalanced in the same fashion. A single 325 will work for the summing or my 2-ACA-Bo card. With my card, you then have a master fader and more iron/DOA's which is not a bad thing. You'd have a mini, basic, mono mixer. Oh, and it would be all discrete!  ;D

Cheers, Jeff

 

[alexc]

Thanks Jeff!

 

[jsteiger]

Thanks Jeff!

No problem. Let me know what you come up with.

 

[Tubemooley]

That is a very, very complicated question right there. We can probably help you (and will gladly). I don't have time to get into this right now. Let me see what I can come up with tomorrow. Where are you located SIXTYNINER? (just wondering). Sincerely, Dana Walcott.

 

[SIXTYNINER]

Hi Jeff

Just wondering if you might have some info on connecting some channel input boards
(such as your mic pre), thru a big fader to your ACA board.

Looking to hookup a simple submixer here - no pan or switching or anything.

I'm not sure how to couple the traffo balanced output from a 312-style board to a reasonably
common 100m fader (2K?, 10K?) and whether an additional post-fader doa might be required.


Thanks
Alex

Hi Alex,
Take a look at the reference docs page on my site. There is a basic sketch Brent gave me years ago. I had a simple 2 to mixer with 312's feeding 440 faders being summed thru the inverting inputs an a 325 card. Same exact principle you are after. The 440's were 600 ohm. 1K faders would work just fine. You could probably even try other fader values if you have those on hand. The output of the preamps is being unbalanced but no biggie. This is essentially how the insert return is on my input channels, unbalanced in the same fashion. A single 325 will work for the summing or my 2-ACA-Bo card. With my card, you then have a master fader and more iron/DOA's which is not a bad thing. You'd have a mini, basic, mono mixer. Oh, and it would be all discrete!  ;D

Cheers, Jeff

jeff
a full list of parts must be got from you (acas,2520doa,325,transformers ecc...)
for "jam" a stereo  summ bus with 16/24 line input (10k impedance)
can be a nice thing
-
i
sent you a pm
let me know
6T9R
cheers
6T9R

 

[plumsolly]

Hello Jeff and all
I'm getting ready to build my 2-ACA-Bo which is going to replace the summing/fader buffer/line output driver amps in my Auditronics 110. I am getting ready to replace the control room monitor section of my console as well. Here is my dilemma: Initially I was going to take the outputs from the booster amp and send them to my control room monitor section - when 2-buss was selected the booster amp outputs would go to my monitors and when anything else was selected a relay would connect the booster amp outputs to my A2D. seems like a good idea right? I am monitoring the exact signal that I will be printing, and when I print a mix, I can just monitor through my converters/computer/record heads, etc. But where I ran into a snag is, I only have 12 D2A outputs, and I would have to sacrifice 2 of them in order to monitor when printing a mix, which would be a pretty big bummer. So I started thinking about using the mult or aux off of the booster amp to drive my control room monitor simultaneously. Here are my questions: If I go the latter route, which booster outputs do I use to drive my meters (aux or mult) and which do I send to my control room section? My control room section is passive and unbalanced, so the output of the booster amp will see a 10k fader, is it ok to drive that fader and my recorder? One of my major considerations is to have the monitored signal be identical with what is being sent to my recorder - I would be worried that when using the aux out of the booster amp to drive my monitors, I would be hearing a slightly different signal because of the difference in turns ratio?
Thanks so much and Best, Ben

 

[jsteiger]

Hi Ben,

This is some complicated ground to cover. I can give you the overview on how it's handled in my console. I don't have finite circuit details right now, I would pull out the schematics out for that if you want.

On the output of my 2-bus 325 cards, I have the balanced lines mult to my (2) 2-track(s) which are (2) 10K input impedance devices. My control room monitoring is active and switchable between a few sources. A mult goes from the above mentioned 2-bus 325's, to a relay board. This board selects what is being monitored at the control room module. Program, tape, 1/2 track, DAT and so on. This is a transformer balanced input stage. The signal for the L-R meters is taken post relay and pre input x-fo, so you are metering what ever source you are monitoring. The meters are IC buffered. The selected source goes from the input x-fo's, unbalanced, to the control room module. Here it is buffered with a DOA. I have replaced these with Hardy 990c's. Next is a 5K monitor dim pot then to a 600 ohm stepped attenuator. The signal leaves the control room module and off to another pair of 325's. These I have also used 990c's on and have replaced the original 2503's with Jensen JT11's. They are as clean as the day is long. The now balanced signal is then off to the monitors(Barefoot's ;D). I bypassed the coupling cap and so on on these cards.

I understand your theory on monitoring exactly what you are printing. It really wasn't feasible in my setup, as the signal structure of the board was set. That is why I replaced the 2520's with 990's and did the JT11's. I am quite alright with my current set up. I assume your meters are buffered? Is the signal going to them balanced or unbalanced? You may consider a simple, ultra clean, balanced receiver, IC circuit to buffer the 10k level pot for your passive monitoring section. That would just go to the mult out on the 325's. The other mult out would go to your "2-track". I would take the meter feed as a mult either before or after the above mentioned IC buffer(depends on balanced or unbalanced). Also, making sure the meter's are buffered, which I'm sure they already are.

I hope this was somewhat helpful. Let me know.

Cheers, Jeff   

 

[plumsolly]

Thanks for the reply Jeff. What your describing in your console sounds similar to what was originally in my console; signal splits off of the 2-buss line driver, goes to an active monitor section, then out to another identical line driver to speakers. I guess I'm wondering how little circuitry I can get away with. I'm thinking again about using a relay to switch where the booster amp output goes (2-track or monitor section). Do you think it would be reasonable for the booster amp to drive just a 10k pot and a buffered meter amp - then go directly to speakers? Or, if I want to have volume control after the master fader, am I just going to have to buffer the volume pot somehow? THAT corp chips? I also wonder if I am going to have to build some kind of line driver stage after the volume pot - it seems that both of our consoles take that approach. My hope is to keep this as simple as possible - both to keep the signal clean and because, as I have no idea what I'm doing, it can easily get too complicated
Thanks so much - I know this goes way beyond support for your (fabulous) products. best, Ben

 

[SIXTYNINER]

Hi Ben,
This is some complicated ground to cover. I can give you the overview on how it's handled in my console. I don't have finite circuit details right now, I would pull out the schematics out for that if you want.
On the output of my 2-bus 325 cards, I have the ....................
 .................our passive monitoring section. That would just go to the mult out on the 325's. The other mult out would go to your "2-track". I would take the meter feed as a mult either before or after the above mentioned IC buffer(depends on balanced or unbalanced). Also, making sure the meter's are buffered, which I'm sure they already are.

hi guys
A nice picture with layout / scheme , can say that millions words cannot
also as help for the forum members that are interested ,
but that are not very "experts" ......
cheers

 

[lotus]

Hello.I have a board as well but I haven't gotten far in any design work. I too would like some insight on what Plumsolly is asking about and that is how best to split  after the line driver stereo bus to both monitor signal and send to record.Thanks Eric

 

[plumsolly]

So I have been turning this over in my head and I am thinking about a 600/600 stepped bridged-t attenuator for monitor volume - So the output of the booster amp is switched via relay between the input of my 2track/a2d and the attenuator - the output of the attenuator goes directly to amp/speakers. I think this arrangement should work well. It's similar (as far as volume control) to Igor's passive monitor controller. For the attenuator, I think the only close to affordable solution is a 6x11 elma switch-  8 3db steps and 2 6db steps for a total of 38db attenuation - (or something like that) It's not a lot of resolution, I know, but there is volume control via the 2-buss fader, computer, etc. Let me know what you think! Best, Ben

 

[jsteiger]

Hey Ben,

Why not just use a mult to the attenuator so you have full time monitoring and uninterrupted feed to your 2-track at the same time? You could mult a feed to your VU's too. Even build a meter buffer with a 100K input impedance so the additional load is minuscule. A good DOA will drive all of these no problem.  ;D

Cheers, Jeff

 

[martthie_08]

quick update, I have now completed my summing / booster amp and it sounds sweet! Actually maybe just a tad too sweet, I have to recheck the calculations for the summing opamp feedback cap again, got a 470pf ceramic disc in there right now with a 3K3 summing resistor. Generally speaking the sound is really mellow (especially in the highs) but altogether very focused, it is great, I like it! I'll see if I can do some measurements that back up my perceptive findings and then I have some pictures to take of the nice board resting inside the Studer! I've also 99% completed a pair of DIY990 to fool around with, right now I have gar2520 amps in the summing and Fabio 2520 in the 325 output stage - stay tuned...

 

[jsteiger]

quick update, I have now completed my summing / booster amp and it sounds sweet! Actually maybe just a tad too sweet, I have to recheck the calculations for the summing opamp feedback cap again, got a 470pf ceramic disc in there right now with a 3K3 summing resistor. Generally speaking the sound is really mellow (especially in the highs) but altogether very focused, it is great, I like it! I'll see if I can do some measurements that back up my perceptive findings and then I have some pictures to take of the nice board resting inside the Studer! I've also 99% completed a pair of DIY990 to fool around with, right now I have gar2520 amps in the summing and Fabio 2520 in the 325 output stage - stay tuned...

Very nice Marten. Is there such a thing as a tad too sweet?!?!  8)

Will be nice to see some pics.

Where did you end up with your feedback R? I know there is a bit of tweaking to maintain unity gain thru-out both amps especially with different summing R's.

Best, Jeff

 

[martthie_08]

yes, this was really exciting, I spent the evening pulling up old mixes and going through iTunes always A/B ing the two mix busses. It does make a rather big difference to a console, as obviously everything will be running through it.

Sorry for being unclear, the feedback resistor is in fact 3.3k and the feedback cap may be a notch too high with 470pF, limiting high end response.

The audio levels are not an issue, it's 0.5 to 1dB at the most, although I do have to measure it.

 

[jsteiger]

...the feedback resistor is in fact 3.3k and the feedback cap may be a notch too high with 470pF, limiting high end response.

Hi Marten,

This will put your -3db point at around 103K if my spreadsheet is right!    Around -0.1db at 20K. FWIW, API always seemed to be between 75K and 100K or so with their -3db shoulder. Maybe this always worked for them with the old 2520's? I suppose you may want to play with the cap values depending on which DOA's end up where on the board. Some people seem to enjoy cleaner summing. Maybe try your 990's in the ACA too with the gar's in the booster section.

As long as you are having fun...

Best!
Jeff

 

[Skylar]

What happened to these, Jeff?

Not seeing them in the store anymore.

Am I blind or just dumb?

 

[kazper]

Inverter is found at http://classicapi.com/catalog/product_info.php?cPath=22_46&products_id=55
ACA is not found