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Project Specific Discussions => Mixers/Monitoring Systems => Topic started by: jsteiger on April 14, 2009, 12:27:22 PM

Title: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on April 14, 2009, 12:27:22 PM
As the title states, this is the official support thread for the 2-ACA-Bo, PCB build that can be found at here http://capi-gear.com/catalog/index.php?cPath=22_46. Per a request in the BM, I felt I should start this thread.

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September 21st, 2015 Update:
All support docs for this project can be found on the recently added Support Docs (http://capi-gear.com/catalog/support_docs.php) page at www.capi-gear.com
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Anyhow, here is a brief history of the creation of this board. Like many projects, I created this for my own personal needs in the rebuild of my console. I am using this board as the 2-mix summing/booster stage of the custom discrete monitor bucket that I'm building. I wanted to match the exact process that API used to complete this task on the main or "input" side of my desk. My board, unlike some others, used the 4 channel ACA's for summing and 325 cards for the post fader booster amps. So, that is what the 2-ACA-Bo is comprised of. This is the exact same method used for summing all the group buses as well.

Per a behind the scenes discussion with Dennis (Prodigy member "API"), here are a few back-side pictures of my desk before my furniture/frame rebuild.

All the 4 channel ACA's are in the middle section. 300 series card cage is on the right.
(http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/back_of_desk_1.gif) (http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/back_of_desk_1.jpg)

And another...cage closed
(http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/back_of_desk_2.gif) (http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/back_of_desk_2.jpg)

The 4 boards to the right are ACA's for summing the 16 sub-groups. The 5th board is 2 channels for Input Cue 1 & 2 summing, and 2 channels for stereo 2-mix, Left and Right of course. These output transformers are the AP2623-4, PCB mount version of the 2623.
(http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/ACA.gif) (http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/ACA.jpg)

From here, the each summed signal goes to normalled points at the patchbay where they create an insert point that is -2db. The return signal is directly wired to the respective fader (group or 2-mix), which were originally 600ohm in my board. That's right, the returns are all unbalanced, and the insert device (if any) is directly driving the fader. The fader output is then wired back to the 300 series card cage.
(http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/300_rack.gif) (http://www.capi-gear.com/catalog/images/gallery/PCBs/2-ACA-Bo/desk_pics/300_rack.jpg)

In the card cage, you see an ass-load of beautiful and underrated 325 cards. These cards are the post fader, booster amps. These are not exactly the 325 circuit that you've all seen the schemo for. They have an obsolete TIS73 that was used to switch between the program source and a slate/tone signal. There is a 10uf input coupling cap and they use the inverting input of the 2520.

In the cage you also see 4-325's that were quad boosters for the control room, 4-325's that were the quad boosters for the studio amps and a single mono program booster.

The output of each sub-group 325 booster goes to the patchbay were it normals to the tape machine inputs. A mult is on this output that feeds a meter buffer as well. The input/group meter buffers are on the monitor cards, where you can switch the metering from input channel or monitor channel. The "direct" switch on each input channel determines if you are metering sub-group or input channel.  ??? Might sound a little confusing but it's really pretty simple.

Besides the 2-mix output, 2 mults are on the 2-mix booster card outputs. The first feeds the L-R meter buffer amps and the 2nd is the feed to the control room module. Of course there, you select 2 track return, CD player or "program" for the source you are listening to in the control room.

This 2-ACA-Bo board is an exact replication of 2 stereo ACA amps and 2 of the 325 amps, with three exceptions. The original ACA input coupling caps were 250uf, mine are 220uf. The output coupling caps are 470uf instead of the 250uf on the ACA's and the 400uf originally found on the 325 cards.

I am happy to help with anything I can on these.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: substitute on April 14, 2009, 08:57:47 PM
It seems like these could be really cool to use for the make up gain after a passive eq.  Would there be any point in using the ACA's and the 325's? 
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 15, 2009, 08:04:07 AM
It seems like these could be really cool to use for the make up gain after a passive eq.  Would there be any point in using the ACA's and the 325's? 
I would assume the 325 side would be all you would need, although a vintage 325 card may be a more versatile choice. The way the 325 cards were designed, you could set them up for many different applications. However, if you look at the going eBay rates for 325's, they would be a lot more costly solution. My cards are only set up the inverting input an all 4 amplifiers, which should not be an issue.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bradb on April 15, 2009, 08:55:38 AM
Sorry, im just not seeing the application for these for people not looking to replace this in their console.

Would it be possible to make a line mixer with level and pan using this as the output stage?

is that what your block diagram is showing on your site.

Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 15, 2009, 09:25:00 AM
Sorry, im just not seeing the application for these for people not looking to replace this in their console.

Would it be possible to make a line mixer with level and pan using this as the output stage?

is that what your block diagram is showing on your site.

This board is designed to be used a stereo summing solution for any unbalanced bus console, line mixer, summing mixer, mic mixer or whatever mixer. There are many home-brew mixers out there that people have built. If you wanna see what a true vintage API style 2-bus solution will sound like, then this may be a board to experiment with. My schemo as drawn, is based on 47K bus resistors, which is what API used in my console and many others they built. If someone wants to modify the feedback R and C on the ACA's, it can be tweaked for whatever gain requirements one may have, within reason.

For the few and brave who are in the process of building from scratch, there very own "console", this is a great solution for all sub-groups, echo sends, cue sends an like I mentioned already, the stereo 2-mix. Or, for someone who ones a vintage 1604 loaded with 528 modules, these boards can be used for the additional buses that aren't currently wired. The push-button switches are on the modules, the traces are on the motherboard but there is currently no summing for them. A very simple addition for that, for sure.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on April 15, 2009, 09:51:56 AM
Would it be possible to make a line mixer with level and pan using this as the output stage?

is that what your block diagram is showing on your site.



1. Yes. This is the main guts. This is the summing amp stage. This is the heart of the line mixer.
2. Yes.

More later. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bradb on April 15, 2009, 10:13:23 AM
i just got a hold of one of those Speck X.Sum line mixers.  better than the standard summing box because it has level on each channel, therefore i can run PTools output signal thru outboard gear and BLAST them, and still turn level down at the line mixer.  I don't have to mix levels using output knobs of outboard compressors, etc. as i would with standard summing boxes.

I think this is the future of mixing.... a hybrid approach, in the box plug ins, and some outboard gear.  it SHOULD beat a console.  we'll see.


anyway, if youre leading up to some kind of api-based, level and pan line mixer, that would be very cool, i'd like to hear more.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 15, 2009, 10:42:22 AM
...anyway, if youre leading up to some kind of api-based, level and pan line mixer, that would be very cool, i'd like to hear more.
Well, if I said that was not rattling around in my head, I would be lying. I have successfully built all discrete line input modules that have 4 Echos, 2 Cues, HP filters, solo, phase flip, pan and of course level. These are a clone or replication of my input channels and sound so much like them it is crazy. They have the balls to easily drive up to 16 group buses along with stereo, just like they do in my board. The format of my custom channels is for the monitor bucket which is an odd 3/4" wide module. I have the desire to rework the layout for something more common, like possibly the upcoming GroupDIY 51X racks. Faders and buses could be added as desired. The circuit is very simple and very easy to build. Oh, and it sounds friggin' great.  8)

I have to speak with Volker about this because I will need to have a completely unique PCB back-plane which is no biggie. I suppose rack mount is the way and may be possible use the metalwork that is now being developed for the 51X racks.

The daisy chain method/theory that is used for the 8200, 7800 stuff would work very nicely.

So, a DIY, all modular, vintage API style mixer. This is so do-able, and ultimately my goal.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bradb on April 15, 2009, 10:47:43 AM
well then, i'll be referring to my Speck x.sum as my "intermediate mixing solution"


keep us posted on what you come up with.  I'm definitely interested.

Like I said, I think a hybrid mixing solution is the future, as level and pan control OTB is better than ITB due to digital limitations (dropping resolution when lowering volume)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: signalflow on April 15, 2009, 11:34:40 AM
Jeff,

Where would one find the schematics for API's Buss routing, pan and fader functions?

-Casey
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 15, 2009, 11:40:27 AM
Jeff,

Where would one find the schematics for API's Buss routing, pan and fader functions?

-Casey
Casey, These I don't have in an electronic format. I tried to get them scanned at Kinko's but they didn't know how to use their large format scanner.  ??? I haven't seen them anywhere else on the net...yet.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: signalflow on April 15, 2009, 12:40:37 PM
Thanks Jeff,

If you ever do get them scanned I would love to take a gander.

-Casey
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Walrus on April 15, 2009, 02:35:29 PM
Take a photo with a digital camera!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on May 12, 2009, 07:00:06 AM
Jeff, I have your beautiful ACA-Booster pcb in the mail and plan to use it as main mix 3-4 output for my Studer console. Now I'm really unfamiliar with summing concepts, so my question is, will one of your API-a-like units be able to sum 24 channels? What is the advantage of having a hierarchical approach with buckets of 8 channels going to an ACA?

I think I will have to adjust the feedback resistor of the 2520 summing opamp to match the Studer channel modules, it seems this will be 3k3 as taken from the existing summing amp info: studer summing amp (http://homepage.mac.com/marten.thielges/studer/image/studer%20summing%20amp.pdf)

I'm hoping to add an alternative (discrete) ouput section to the existing main 1-2 mix output, which is currently just a summing amp (http://homepage.mac.com/marten.thielges/studer/image/summing_amp.gif) going straight to an  output amp (http://homepage.mac.com/marten.thielges/studer/image/output_amp.gif)

Thanks and 2 thumbs up for all your research work! Marten




Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 12, 2009, 07:28:07 AM
Jeff, I have your beautiful ACA-Booster pcb in the mail and plan to use it as main mix 3-4 output for my Studer console. Now I'm really unfamiliar with summing concepts, so my question is, will one of your API-a-like units be able to sum 24 channels? What is the advantage of having a hierarchical approach with buckets of 8 channels going to an ACA?
Marten,
The ACA's on my card will easily sum 40 or more channels. They were summing 36 in my desk with no problems, nice and quite. The 8 channel inverting cards are not necessary at all. I have added these so that when I complete my mods, I can dump my new, all discrete monitor section to the main 2-mix. Without the pre-summing, I would have 72+ channels being summing thru 1 ACA pair. The noise would be unacceptable for sure.

If you modify the feedback R, remember to also adjust the feedback C to limit HF and prevent weird oscillations.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: RyanC on May 13, 2009, 10:28:41 AM
This looks like exactly what I'm looking for-

I'm looking at building a 34x8x2 routing mixer that would be just L and R buss assignments.  So either 4 of these and passive 2 bus or just 5 of these seem to fit the bill.  The summing thing is new to me also.  I'm trying to understand, will there be any issues if I were to route one channel to multiple busses?

Also the 34 ch would be fed by an (unbal) mackie ultramix VCA auto system.  Is there any issues with that?

Thanks
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 13, 2009, 09:39:27 PM
...will there be any issues if I were to route one channel to multiple busses?
In speaking of my desk, I have 16 buses plus the stereo bus that are assignable for each channel. All bus resistors are 47K. No issues in assigning a channel to all 16 buses.
Quote
Also the 34 ch would be fed by an (unbal) mackie ultramix VCA auto system.  Is there any issues with that?
The channel output that feeds all the buses is unbalanced. So, the busing in my console is all unbalanced as well.

Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Engfelt2000 on May 23, 2009, 10:11:09 AM
Hi Jeff. Any progress on your line input modules? I'm really eager :)  And judging by the response on the new Igor cult thread, quite a few others wants to build a mixer as well.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on May 26, 2009, 01:55:45 PM
ok, a little progress here, some notes: I started by building only the output amp and hooked up to my existing summing amp. It would have been nice to have all the connectors on Molex type pin spacings and there are no explicit solder pads for R15 and R16 (but no biggie, you can place them in the positions for Q1 and Q2).

Everything worked on first power up and I am impressed. In direct A/B comparison to the Studer output amp the API is really focused and defined. The Studer amp sounds more open, quite flattering and really exciting in the highs. I am sensing this will give me some really useful options when mixing upcoming projects!

There is a 0.6dB level drop on the API, but it might be because I am running it on +/- 15V and come to think of it, it may also be a +0.6 DB boost on the Studer, cause the Studer is adjustable up to 30 something dB... now the Studer amp is going to the Black Market to make some spare change for the API summing section, please have a look if you are interested!

more to come...
cheers, Marten
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 27, 2009, 12:23:09 AM
...It would have been nice to have all the connectors on Molex type pin spacings
Hi Marten,
Sounds like good news so far!  ;D  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?

Quote
...there are no explicit solder pads for R15 and R16 (but no biggie, you can place them in the positions for Q1 and Q2).
Correct-amundo on this one. The original design was for me and my console use. I am using the N channel switches to work with my existing boosters. I thought it would be nice to make that part of the circuit optional. I did try to show this on the skiz but never really specified that you need the stand up the 24.9 ohm resistor and use the gate and source holes of Q1 and Q2.

Quote
Everything worked on first power up and I am impressed...
Always good news. Keep us posted when you get the ACA stages all populated an wired in.  ;)

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on May 27, 2009, 04:52:25 AM
Quote
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!!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: alexc on May 29, 2009, 02:18:15 AM
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


Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 30, 2009, 03:35:36 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: alexc on May 30, 2009, 06:41:09 PM
Thanks Jeff!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 30, 2009, 07:56:56 PM
Thanks Jeff!
No problem. Let me know what you come up with.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on June 11, 2009, 06:41:40 AM
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.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: SIXTYNINER on June 23, 2009, 12:19:22 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on June 29, 2009, 09:35:53 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 01, 2009, 08:41:32 AM
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     
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on July 01, 2009, 10:45:55 AM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: SIXTYNINER on July 02, 2009, 07:16:16 AM
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
 :o
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: lotus on July 02, 2009, 03:04:46 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on July 07, 2009, 04:32:34 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 07, 2009, 09:54:26 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on July 20, 2009, 03:30:13 PM
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...
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 20, 2009, 08:26:56 PM
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
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on July 21, 2009, 06:05:47 AM
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.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 21, 2009, 07:59:22 AM
...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... :D

Best!
Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Skylar on August 02, 2009, 01:28:41 AM
What happened to these, Jeff?

Not seeing them in the store anymore.

Am I blind or just dumb?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kazper on August 02, 2009, 04:33:04 AM
Inverter is found at http://classicapi.com/catalog/product_info.php?cPath=22_46&products_id=55
ACA is not found
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 02, 2009, 09:20:30 AM
What happened to these, Jeff?

Not seeing them in the store anymore.

Am I blind or just dumb?
Hey Skylar,

You are neither blind nor dumb my friend!  8)

I ran out quick at the end. I have more on order. I should have them in about 9 or 10 days. I will update the item so it shows the date expected. I forgot to do that so thanks for the reminder!

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 02, 2009, 09:25:23 AM
Inverter is found at http://classicapi.com/catalog/product_info.php?cPath=22_46&products_id=55
ACA is not found
Thanks kazper.  ;)

ACA is now visible again with date expected at http://classicapi.com/catalog/product_info.php?cPath=22_46&products_id=81

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Skylar on August 02, 2009, 01:16:54 PM
Cool!


I just bought a 42-channel Wheatstone SP-5a broadcast console.

I was thinking about replacing the master bus with a 2-ACA-Bo or a Neve 1272 line amp.
Maybe I'll try both...hmmmm.

(http://i73.photobucket.com/albums/i222/skylargray/SP-5a/th_SP-5a01.jpg) (http://s73.photobucket.com/albums/i222/skylargray/SP-5a/SP-5a01.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on August 17, 2009, 06:08:47 PM
Hey Jeff, I was thinking about using the my 4-aca card for buss summing. It would be the output of each aca to an unbalanced insert point normalled to a fader and then sent to the 2-mix. Or something along those lines. Does that sound reasonable to you? - Thanks and Best, Ben
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: 3nity on August 17, 2009, 06:46:14 PM
Hey Skylar i really dig that mixer...
I'm looking for a decent mixer 32 channels who knows!!
It looks great!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 17, 2009, 09:48:16 PM
Hey Jeff, I was thinking about using the my 4-aca card for buss summing. It would be the output of each aca to an unbalanced insert point normalled to a fader and then sent to the 2-mix. Or something along those lines. Does that sound reasonable to you? - Thanks and Best, Ben
Hey Ben,

One thing to keep in mind is that the Inv-ACA is an inverting only ACA. To interface with the outside world, you will have to invert the phase again. Easiest way is with a transformer. If you look at the 2-ACA-Bo skiz, you will see that I am inverting the phase with the 2623 style trafo. Basically, if you add a 2623-x after each of the separated outputs of a JLS-Inv-ACA card (not bussed together and no 47K buss R's), you have the first half or ACA only part of the 2-ACA-Bo card. I hope that makes sense.

Yes, an insert point normalled to a fader, then thru a 47K buss R is API style all the way.  ;D

And yes Skylar, I agree with 3nity. Nice looking desk.  8) Your new bolster really makes it! Is it fully functional or a work in progress? What kind of fun would fully functional be?!?  :D

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Skylar on August 19, 2009, 12:04:55 PM

And yes Skylar, I agree with 3nity. Nice looking desk.  8) Your new bolster really makes it! Is it fully functional or a work in progress? What kind of fun would fully functional be?!?  :D



Thank you 3nity & Jeff!


*Unfortunately*, this desk is fully functional!
Inputs are all line-level, EQ actually sounds really nice, has a cool control room section, and is pretty basic otherwise.

All the summing is unbalanced, so it seems more appropriate to drop in a 2-ACA-Bo rather than a balanced input 1272 Neve-y thing.
Besides, the power rails are +/- 17V, and I don't feel like building a separate 24V supply just for a master bus summing amp.

This project is down on my list right now, though, behind two or three other things.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on August 19, 2009, 07:43:11 PM
(http://i164.photobucket.com/albums/u14/Garbagelarge/1608_blockbus.jpg)
In this block diagram of the bus section of the sixteen-o-eight it looks like they have the bus fader buffered before it goes into the stereo bus. So I guess I would want to use 2-aca cards for each pair of buses, stuff everything except the 2503's and run the outputs through 47k resistors to the stereo bus. I guess this way maybe I could put a pan pot between the output of the bus buffer amps and the stereo bus - that way my mono buses wouldn't have to be left, right, or center only...
-Ben
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: THE BAD DOGS on September 25, 2009, 05:59:03 PM
Hello,

I want to use your 2 aca booster in the master section of my soundcraft 600. Where can i connect the module?

Schematic : http://img29.imageshack.us/i/soundcraft600mastersect.pdf/

Thanx,
Jean-Christophe
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on September 27, 2009, 09:06:23 AM
I have nearly finished my ACA board & am looking to make a box to mix direct from my digi 002 rack. I thought before I started to hook this up I would just run it past you guys, to see if anyone any ideas to improve my idea, or tell me why it's not good.

I was thinking of trying to make the unit so I had 8 mono feeds  for vocals, guitars etc & 4 stereo feeds for drums etc   Is this a reasonable configuration or would it be better as 3 st & 10 mono  etc  ???

I also wanted to make all the inputs go through a normalised B gauge patchbay so that I could insert real compressors & eq's.
One of the things in my head is I'm wondering if I am inserting different compressors between the 002 rack & the ACA with the differing output impedances from the compressors will screw the gain structure for the ACA when comboning with mix resistors ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on October 04, 2009, 12:31:01 PM
Bumping my previous post

Also I'm wanting to add a 2 buss insert point.  I'm think that this might want to go after the ACA but before the fader.  Would it be pertinant to add a balanced insert buffer before the fader since I don't have any unbalnced gear I would be inserting at this point ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on October 04, 2009, 02:01:26 PM
Would it be pertinant to add a balanced insert buffer before the fader since I don't have any unbalnced gear I would be inserting at this point ?
You are talking about adding a debalancing circuit before the fader? I'm not sure this is necessary - In the original design, with nothing inserted, it will still be balanced ACA output > unbalanced fader. So i assume it is ok to drive the fader with balanced gear, but perhaps the design is from a time when things were either unbalanced or transformer-balanced - I still don't understand the difference in implementation between 'electronically balanced' gear and transformer-balanced. Not sure if that makes this any less confusing. Best, Ben
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on October 04, 2009, 03:05:41 PM
That seems to make sense, thanks Plumsolly
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 04, 2009, 04:24:12 PM
Ben is right. With nothing inserted, it will be a balanced ACA output feeding an unbalanced fader input. The fader wiring will unbalance whatever comp or eq you have inserted by connecting the low side of the balanced signal to ground. Probably won't be an issue for most gear. Like Ben mentioned, when my desk was manufactured, most gear had transformer balanced outputs.

On a similar topic, this is why the API eq modules have an unbalanced input and a transformer balanced output. They were designed as part of the input channel "strip", if you will. The unbalanced eq input is driven by a 2520 into a 2623-1 transformer(on the input channel). The eq output drives the channel fader. Balanced output to an unbalanced fader, same concept as the insert point on the ACA.

Rob, as far as the inputs you mentioned, that will be a console sort of structure. Your mono inputs will have to be split into (2) 47K buss resistors. You will have to find the proper value resistor to put just before the buss R's to get a 3db, 4.5db drop or whatever you want for a mono signal. You will be unbalancing the outputs of whatever gear you are combining with the ACA. Shouldn't be an issue at all unless you are running 100' cables between everything.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ask on October 04, 2009, 04:50:53 PM
There could be an issue with typical electronically balanced outputs (which most modern gear has), since you are, in essence, shorting an amplifier (low/cold/neg./pin 3) to ground, it COULD misbehave, which MIGHT affect the high/hot/pos./pin 2 signal - you could lose headroom and/or get increased distortion.

The quick fix is to leave the negative (pin 3) open/disconnected, just make cables that don't ground it!

*NOTE: a RARE variety of electronically balanced outputs react like a transformer, which needs to be shorted to ground in order to get an unbalanced signal from it. *

Ben is right. With nothing inserted, it will be a balanced ACA output feeding an unbalanced fader input. The fader wiring will unbalance whatever comp or eq you have inserted by connecting the low side of the balanced signal to ground. Probably won't be an issue for most gear. Like Ben mentioned, when my desk was manufactured, most gear had transformer balanced outputs.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 04, 2009, 05:13:55 PM
I use to have a few "special" patchbay cables that had the low pin floating on one designated end for these situations.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on October 04, 2009, 05:23:32 PM
Thanks for this info guys, will get onto it tomorrow, & report.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on October 04, 2009, 06:15:41 PM
I was just wondering whether it is better to terminate the unused cold signal of an electronically balanced output to ground rather than leave it floating, when running into an unbalanced input ??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ask on October 04, 2009, 06:26:42 PM
Normally no, as I've tried to explain. You wouldn't ground an unused side of a power amp if you only used one speaker, would you?

(What you want to ground is an unconnected INPUT, so it doesn't act as an antennae, and pick up stray noise)

I was just wondering whether it is better to terminate the unused cold signal of an electronically balanced output to ground rather than leave it floating, when running into an unbalanced input ??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Rob Flinn on October 04, 2009, 07:39:02 PM
Normally no, as I've tried to explain. You wouldn't ground an unused side of a power amp if you only used one speaker, would you?

(What you want to ground is an unconnected INPUT, so it doesn't act as an antennae, and pick up stray noise)


Sorry, what I meant to say was terminate through a resistor, & no I wouldn't terminate the unused side of a power amp !!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ask on October 05, 2009, 02:31:43 AM
That's good :D

...I wouldn't terminate the unused side of a power amp !!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: mylesgm on October 23, 2009, 04:05:56 PM
So Thinking about building a stand alone simple line summing box.  Like the idea of doing api way and I'm wondering about balanced inouts prior to the 47k resistors.  So I've got a pile of astor/awa 1:1 line transformers and was going to do 16 inputs via transformers then on to the 47k resistors and the rest of the circuit.  Will this be suitable and could I add a pot before the 47k for attentuation?  Also, how could I add multiple outs to the master out?  I would like to return 2 channels to the daw and a 2 channel split to go to the studio monitor selector.

thoughts?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 25, 2009, 11:19:08 AM
So Thinking about building a stand alone simple line summing box.  Like the idea of doing api way and I'm wondering about balanced inouts prior to the 47k resistors.  So I've got a pile of astor/awa 1:1 line transformers and was going to do 16 inputs via transformers then on to the 47k resistors and the rest of the circuit.  Will this be suitable and could I add a pot before the 47k for attentuation?  Also, how could I add multiple outs to the master out?  I would like to return 2 channels to the daw and a 2 channel split to go to the studio monitor selector.

thoughts?
The 1:1 transformers and the level pot before the 47K buss resistors would be a fine idea. Check out this link (http://www.classicapi.com/catalog/images/reference_docs/Brent-MJ.pdf) for something similar. For multiple outputs, I have the boards set up with a 2nd output already via a simple mult. You could easily add a 3rd if you wanted with no real change.

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: conleycd on January 10, 2010, 11:13:49 PM
Jeff's summing amp is definitely on my list of DIY projects to do.  I have to finish my other commitments first but I've been planning this one for a while.

I'm planning a bit of weird box.  Essentially, it is combining amplifier (2 actually) with some main mix sends and returns for parallel processing, some VU monitoring/metering, maybe some patchable stereo spreaders.... blah, blah... the list grows - hopefully to eliminate the size or need for a console (so I have to slim down a little!).

My thought is to actually use Joe Malone (JLMaudio)'s JLM99vs.  Joe makes great stuff, I'm also a sucker marketing so when I hear "Neve on steroids" I'm lost in potential mix ecstasy.  That along with the idea of running 34v +/- for huge headroom is kinda hot too.

Anyway... I've been thinking back and forth between iron or opamp for the polarity reversal coming out of the combining amplifier (my box will actually have 2 stereo combining amplifiers).  The first one can remain unbalanced but really needs to be proper polarity.  The price is about the same either way.  Ed's transformers or a nice DOA (mind you it is just at unity - so no real thrill) is around $30. 

Any thoughts opamp for polarity or transformer?

CC
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on January 27, 2010, 03:12:14 PM
OK, I've been meaning to do this for a long time, but I've finally managed to get a frequency plot of my modified studer and the measurements pretty much go hand in hand with my subjective observations. Please note that I have changed the resistance and capacitance for adaptation to my specific console.

(http://homepage.mac.com/marten.thielges/studer/image/studerapi.png)

The Studer summing on mixbus 3-4 is the orange graph and the api summing on mixbus 1-2 is the blue graph, recorded through the same converter. Both the level drop (1dB) and the limited HF response tell me that something still needs tweaking. I have come to like the overall sound of the API summing and although the vertical dimension are pretty extreme on the above image, it would still be nice to get a tad more high end out of it. I might try a smaller cap in the summing amp, but maybe the problem is in the 2520 opamps not being fully happy at -/- 15V

Anyways, if anyone else would like to see a diagram of their main bus frequency response (preferably with the 2-ACA-Bo), rum this sine sweep (http://homepage.mac.com/marten.thielges/studer/sweep.wav) through your console (watch your ears!), send me an email of the recording and I'll post a chart.

cheers, Marten
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on January 27, 2010, 03:47:57 PM
Very interesting Marten. Do you have a comparison of maybe the channel direct out as well? It would be fun to see if the input channels stay more flat near 20k or if the slight roll off is all from the summing stage.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on January 27, 2010, 05:11:09 PM
yes, here is the channel direct out response in green, the level is a bit different, I am on a different mix right now  8)

the high end frequency response of the direct out is very close to that of the studer summing section (aside of the global difference in audio level).

side note: I wish my "speakers in the room" response would like any of those charts  ;)

(http://homepage.mac.com/marten.thielges/studer/image/studerapidirect.png)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: conleycd on January 27, 2010, 09:09:52 PM
Hmmm... you would expect the high to be a little more level.  I think 2520s love 15v +/-.  This should really affect primarily your headroom.

Are you using a capacitor on the way into the mix bus?  What is it's value?  I don't fully understand why your direct channel looks the same way too.  What's creating a low pass perhaps unexpectedly.

Cables with roll off?  I dunno?

CC
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on January 27, 2010, 11:35:19 PM
Is the API plot of both stages or just the first ACA stage? The customary API gain structure is -2db after the ACA with 12 db of gain in hand at the 2 mix fader then +4db of course after the 325 booster section.

I remember you modified the feedback R and C to match with your buss R's??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: martthie_08 on January 29, 2010, 04:56:05 AM
Quote
Hmmm... you would expect the high to be a little more level

well, yeah measurements are often a bit off at the extremes of the measurement, but it is the relative graph between studer summing / studer direct out and the api summing that shows a qualitative difference. I should repeat the measurements at 96KHz or 192KHz, hadn't really thought of that as I always record at 44.1KHz.

Quote
s the API plot of both stages or just the first ACA stage?

both stages - I will repeat the measurement and check levels taking the signal at the inserts before the 10K Alps pot that sits in front of the 325 booster stage.

Quote
I remember you modified the feedback R and C to match with your buss R's??

yes I'm using a 470pf cap with a 3K3 resistor and I have a feeling the problem lies there. Maybe I will replace the 3K3 resistor with a 5k pot to fine tune the gain and then recalculate the capacitance needed.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: plumsolly on February 01, 2010, 06:03:33 PM
I graphed the frequency response of the 2-ACA-equipped 2-buss in my Auditronics 110 console along with a direct out for comparison: (http://i164.photobucket.com/albums/u14/Garbagelarge/apibuss3-compare.jpg) The blue is the 2-buss out (post 2-buss fader) and the red is the direct out (pre channel fader and bypassed eq section: it would have made more sense to measure the direct out after the channel fader and eq but I didn't, so oh well) at first glance it looks pretty poor, but the resolution on the y-axis is .2db, which I did to be consistent with Marten's graph. The response of both of my outputs is flat +/- 1.5db. Marten's is flat +/- .5db. Also, the 2-buss out on my console is very very close to the direct out. The difference between the direct out and 2-buss on my console is pretty similar to the difference between the direct out and the 2-buss on Marten's console, which would suggest that your cap and resistor modifications on the aca board are providing a similar result to using the stock values and 47k buss resistors - which is what are in my console. Anyways, I am plenty satisfied with the response of mine ... Best, Ben
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: RyanC on February 05, 2010, 01:58:01 PM
Hi Jeff-

So I'm looking to price this out for a larger matrix mixer, what would be the pot/fader values (pan and level)?  And are there any specific parts you would recommend?  I'm looking at a 34x20 matrix mixer, with stereo buss assign, pan and level (probably on a pot to save space) on each mono input.  Does panning require extra buffer circuitry, or just a linear pot?

Also, on the matrix mixer, I wont need a meter or an insert point (would just insert post mixer) so is the 325 half necessary if the -2dB level is not a problem for me?  The output of the ACA half of the card is balanced right?

If it helps, I'm looking to use the matrix mixer half during tracking for cue sends, routing and printing of parrallel fx chains etc, and then at mix time have DACS->OBFX->VCA auto/recall-> API Matrix->OBFX-> DAW with all 10 stereo stems back to daw.  And then print all the stems, so only the relevant stem would need to be recalled.  Just throwing that out there to see if anyone has any ideas.  Thanks
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 06, 2010, 10:49:15 AM
Hi Jeff-

So I'm looking to price this out for a larger matrix mixer, what would be the pot/fader values (pan and level)?  And are there any specific parts you would recommend?  I'm looking at a 34x20 matrix mixer, with stereo buss assign, pan and level (probably on a pot to save space) on each mono input.  Does panning require extra buffer circuitry, or just a linear pot?
Ryan, to answer the above would be a text book worth of data! That is more about "input channels" than the ACA part of the console. This build is more about what comes after the input channel, the ACA. I would recommend many searches here and also picking up the book "The Handbook for Sound Engineers". I also remember John Roberts posting a link here to a rather large and great article he had written on console design and architecture. This will also be helpful.

Quote
Also, on the matrix mixer, I wont need a meter or an insert point (would just insert post mixer) so is the 325 half necessary if the -2dB level is not a problem for me?  The output of the ACA half of the card is balanced right?
Yes the ACA output is transformer balanced with 2623-4's. The polarity is properly inverted with the primaries of the 2623-4. The booster or 325 part of the circuit is not 100% necessary.

Cheers! Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: RyanC on February 06, 2010, 12:46:49 PM
I was afraid of that. . . time to hit the books.  Thanks jeff.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on March 08, 2010, 08:58:31 AM
Dear jeff: I'm new in this forum . I want to tell you that I love What you are doing  at classicAPI. I have an API 2488 from 1972 ,If you need any schematics just ask for it, With 528 modules and 550 A eq's . And my question is , my console doesn't have any cards like your's ( 312 or 325 ), I want to know if the summing stage is like yours with almost a 325 cards after de st fader , Because i see the st and busses aca , but dont see the oder stage.
I'm trying to built a mini console with a replica of the 528 modules without the cue sends and aux send,only the line/mic and the 1 and 2 buttons for the low filters , and the pan and st / busses assign . Then I will need you ACA bo cards and transformes , i already have scott's sl 2520 vintage and some vintage 2520 originals.
Best Regards
Pedro Pearson.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 08, 2010, 09:32:11 AM
Dear jeff: I'm new in this forum . I want to tell you that I love What you are doing  at classicAPI. I have an API 2488 from 1972 ,If you need any schematics just ask for it, With 528 modules and 550 A eq's . And my question is , my console doesn't have any cards like your's ( 312 or 325 ), I want to know if the summing stage is like yours with almost a 325 cards after de st fader , Because i see the st and busses aca , but dont see the oder stage.
I'm trying to built a mini console with a replica of the 528 modules without the cue sends and aux send,only the line/mic and the 1 and 2 buttons for the low filters , and the pan and st / busses assign . Then I will need you ACA bo cards and transformes , i already have scott's sl 2520 vintage and some vintage 2520 originals.
Best Regards
Pedro Pearson.
Hi Pedro,

Great console you have there. From what I have seen, the 2488's did not have the 300 series card cage. Our friend Dennis in Sweden has confirmed this a few times with the various 2488's he has owned or does own now. What they did was use the 4 channel ACA boards for multiple purposes. Some are populated as the ACA circuit and some are populated exactly the same as the 325 card booster circuit. The only difference is the output transformer on yours is probably a 2623-4 instead of the 2503 found on the 325. Quite interesting how they did this. I don't know why exactly. Space in the console frame maybe?

It's kind of like the input channel PCB's. The boards that are used for your 528 modules are the same exact boards that are used for my 536 modules, which are the same as used for the 544 modules found in the 1604's. They would just populate the boards a little differently and use different faceplates and switch caps. Kind of genius I think.

BTW, my board does not have the 312 cards. My pres are on the 536 input modules just like yours.

I am planning on a 500 sized modular desk that uses the vintage API input channel. I have the modules layed out already. If you search for "500 modular console" you should find the thread here in the Lab.

Cheers!
Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on March 08, 2010, 05:28:04 PM
here the picture, API TRANSFORMERS SPEC.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on March 08, 2010, 05:45:26 PM
my post didn't show up.... Don't know why .
But jeff : I was saying that the aca boosters only have the 2623. the 2503 are inside the 528 modules 2 of them , 1 is for the insert going to the patchbay and the other is the multi out channel going to pachtbay too. The directs out of the modules are aca booster cards in the back of the console y think every output is going thru those cards.Also de submasters too.
So i found that the 2623 and the 2503 are pretty much the same, the 2503 has another secondary than the 2623. So the sound will be pretty much the same.In my other post is the picture .
I will build my small api 16x8x2 summing with mic/pre like the 2488 , but without first the cue sends and aux send , may be i'll add that later.
First i want to sum .
Do you have any ideas on cloning the 550A EQ ? I think the difficult part is getting a replica for the caps keys . Any ideas on that ?
I think Api is using a different thing on the 550B, but i didn't see one of them.
Thanks for every thing Jeff. I love to have someone to chat about my API.
Best Regards.
Pedro.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 08, 2010, 10:35:42 PM
...the 2503 are inside the 528 modules 2 of them...
Pedro, are you sure about this? My input channels have 2623-1's on them. I don't see how 2503's would fit on the boards. They would not fit between the DPDT Schadow switches and the channel peak circuit. I have 2 544 channels here from a friend's 1604. One module has a single 2623-1 (no direct out) and the other channel has 2 of the 2157's. They are also the smaller transformers with 2 secondaries. I would not be surprised if maybe your modules were custom? I know API did a lot of custom work back then. Almost all of their consoles were different in some way or another.

Quote
Do you have any ideas on cloning the 550A EQ ?...
No, on this one I don't. It will take a bigger man than me to tackle the 500a. I think maybe Peter Purpose could do it for sure.  :-* :o ;D Common Peter. I double dog dare you!  :)

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on March 08, 2010, 10:46:50 PM
JEFF : DID YOU SAW THE OTHER POST WITH THE PICTURE THAT HAS THE SPEC FOR THE API TRANSFORMERS ? THERE YOU CAN SEE THAT THOSE XFORMERS ARE THE SAME....I WILL PULL OUT A MODULE TO SEE WHAT I'VE TOLD YOU BEFORE.
BUT I'M ALMOST SHURE ABOUT THAT. I WILL TAKE SOME PICTURES.
AN ABOUT THE 550A WHEN YOU SELECT A FREQUENCY THE ROTARY SWITCH SELECT A DIFERENT CAPACITOR SO THAT IS WHAT THE ROTARY SWITCH DOES. IF SOMEBODY HAS AN 550B ,COULD YOU OPEN AND TAKE SOME PICTURES OF IT?
THANKS. REGARDS.

PS: I 'VE POSTED MY OPINION ABOUT THE MODULAR CONSOLE 500 SERIES.

PEDRO.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: SIXTYNINER on April 13, 2010, 04:15:59 PM
 8)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on April 25, 2010, 09:06:01 PM
Hey Jeff
I just got the first of your aca boards,my plan is to build a 24 ch summing mixer with them,I may use differant doas on each bank of 8 chs ....
I am a newb in builds so I am just getting my feet wet in this,I want to start with 2 chs and experment with   
Differant things..
So if I get a 2520 kit,2 2623's and 2 2503's will this get me going, +pwr supply??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 25, 2010, 09:25:05 PM
Yes, as far as what I have at the store. You will need a stereo fader of some sort and the rest is just smaller bits like Molex connectors, some C's, some R's and a couple of diodes.

PS, I only have a few of the PC mount 2623-4's left on hand. Ed is doing another batch but it may be 5 or 6 weeks before I get them in.

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on April 25, 2010, 10:09:12 PM
The fader can be a pot like the one one the monitor out on the new 1604s?
Do you sell that bigger API style knob?
To have a balanced line in do I need trfos or can in go into the doa's , and as for panning per ch , how is that done with the Aca?
I hope to order those trfos this week if I can..
Thks
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on April 27, 2010, 06:25:36 AM
I'll weigh in briefly on one of those questions. To get balanced line in, you can do transformer-balanced input with a line-level transformer. Or you can do what's called a balanced-transformerless amplifier or BTA. You can send a balanced signal into one DOA and then the output of that DOA can dump onto your summing bus. Go to Jeff's website and go to the documents section. Look for the API doc which shows different configurations of the 2520 amplifier. One of them is the BTA. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on April 27, 2010, 08:28:44 AM
I'll weigh in briefly on one of those questions. To get balanced line in, you can do transformer-balanced input with a line-level transformer. Or you can do what's called a balanced-transformerless amplifier or BTA. You can send a balanced signal into one DOA and then the output of that DOA can dump onto your summing bus. Go to Jeff's website and go to the documents section. Look for the API doc which shows different configurations of the 2520 amplifier. One of them is the BTA. DW.

So, there is a bunch of discussion on page 3 of this thread on just this topic.  It would seem that in the case of electrically balanced outputs from whatever is plugging into this thing, that floating pin 3 is acceptable.  I've just got my 2-ACA together yesterday, so I'm doing a little testing here with just that.  Having some oddball results so far, but I'm fairly certain that it's my grounding situation (isn't it always?).

Of course, it would be rather nice to use an input transformer.  Jensen has a very good doc on this at http://www.jensen-transformers.com/an/an003.pdf.  But, that would get VERY pricey when you start getting up into lots of channels with this thing.  I had a look at the BTA layout in the doc on Jeff's web site, but it's a little hard to see so I'm not sure what to make of it.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 27, 2010, 03:12:41 PM
...I had a look at the BTA layout in the doc on Jeff's web site, but it's a little hard to see so I'm not sure what to make of it.
Also take a look at the "API 325 Operation Ref." near the bottom right of the ref docs page. They have a much more clear description of a Balanced Differential Input Amplifier which is more or less the circuit that was used in the consoles. It is the same circuit that Tubemooley was referring too. He is psycho BTW and probably off his meds, so be careful!  :o Just kidding Dana you Q8 maniac!

As far as floating or connecting the Lo side to ground, it will probably be gear dependent. I do this with a few special patchbay cables that have pin 3 or Lo floating. By using a standard patch cable I am connecting pin 3 to ground within the PB jack.

Also, FWIW, within my console, the shield of almost every cable run is floating at the source and connected at the destination.

The fader can be a pot like the one one the monitor out on the new 1604s?
I am not exactly sure what they are doing on the 1608's. I would gather it is quite a bit different than the old desks. It is for a different purpose but could possibly work.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on April 27, 2010, 03:54:04 PM
As far as floating or connecting the Lo side to ground, it will probably be gear dependent. I do this with a few special patchbay cables that have pin 3 or Lo floating. By using a standard patch cable I am connecting pin 3 to ground within the PB jack.

Also, FWIW, within my console, the shield of almost every cable run is floating at the source and connected at the destination.

Makes sense to me - same thing we do in telecom.  Copper is always grounded on only one end in order to avoid group loops.

I think that I'll be ok with leaving the lo floating.  Seems to be working well in my testing so far.  Perhaps I'll put a small switch on the back on the case on the input to connect it to ground or not as needed.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on April 27, 2010, 07:35:16 PM
Thks guys,I am still getting my head around the summing amp doa ins,do I need acas for left and right?
I want to have many stereo pairs with a few mono switches like the Dgr stuff.
The more I think about ,I don't need level controls that can all be done from PT,
I just want the clean discrete signal path to the iron for color?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on April 28, 2010, 05:47:18 AM
It is the same circuit that Tubemooley was referring too. He is psycho BTW and probably off his meds, so be careful!  :o Just kidding Dana you Q8 maniac!
Cheers, Jeff
That would be a big 10-4 good buddy. Psycho? That's an understatement. But I am taking my meds. I just wish my tin foil helmet did a better job of keeping those voices out of my head. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on April 28, 2010, 05:58:57 AM
Go to that document which Jeff pointed to on his website... "API 325 Operation Ref." near the bottom right of the ref docs page. It's an 8-page .pdf. Go to page 3. That's the circuit right there. Balanced input to one DOA. Output goes to a transformer (of course) on a 325 card. For a clearer version of some of those API doc's, go here.... http://www.danalexanderaudio.com/api.html     .... Watch out..... His site gives these idiot pop-ups. Go down to "Op Amp 2520 #2" and look at Figure 4 Balanced Transformerless Amplifier. The 325 line amp has variable gain (with a pot) while the BTA shown in figure 4 is fixed gain of 20dB (set by the resistors). Plus the BTA has those 10k resistors on the inputs to load the source properly. Those two circuits are pretty similar. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on April 29, 2010, 09:41:00 PM
Thks Tubemooly
those links are very good, if I do the line amps I will need a card for allthat, then I am I want to add some pres to it if I am that far?
Will the 312 pcbs on here work?
Also think about having a neve type trsfo option out that could be switched??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on April 30, 2010, 09:01:44 PM
I think the balanced line in doa is the way to go,I can then use different doa's for more sound choices,all with the same 2520 footprint...
Who on the board could make an 8 ch pcb for line input to 2520's?
And what kind of pwr supply is needed to run 32 or more doa's ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on May 02, 2010, 11:47:26 AM
So, this thing is coming along quite nicely.  I have a perfectly working 2 channel mixer right now, with LCR assigns on each channel.  Just waiting for my switches to do the other 14 channels.

I do however need a little power advice.  I'm a PSU dummy, so I really don't know where to look for these things and my searching here and elsewhere hasn't yielded much.

People have designed and make available lots of power supplies for preamps which make +/- 16 or 24 and +48.  In fact, I have the real nice FiveFish 2448 supply running the thing right now for testing.  What I'd like to do though, is build a dedicated +/- 16 only supply for this project.  I also want it to be big enough to power the 2-ACA+Booster and 4 of the 4-ACA boards (although I'm only running 1 right now).

If anyone can point me in the direction of a PCB or something, I'd sure appreciate it!

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 02, 2010, 01:20:52 PM
Good news Brian.  8)

Did you slug the switch to give you some sort of voltage drop when in the center position? This is possibly being handled in PT or ITB some way. Maybe you don't need this.

So, 4 Inverting ACA boards and a single 2-ACA-Bo card is 20 discrete opamps. Typically, a 2520 style amp will draw around 22-25mA when idle and around 50-52mA when driving a 600 ohm load. That's per rail. That has been my experience anyways. So worst case you will draw 52mA times 20 DOA's is 1040mA or just over 1A. I would gather any supply that will give you 1.2-1.5A will be fine. Actually, the DOA's on the Inverting ACA cards will never draw that much as they have a very small load. You may not find a dedicated 2 rail, bipolar PSU project around. There may be one but I don't recall seeing it. Not to pimp but you could always get a 51x PSU PCB and only build out 2 of the rails. Leave the rest of it unpopulated. Maybe someday in the future you could build out the other main bipolar rails for +/-16V or whatever. Same with the 48V section. Just don't build it. Just a thought.

Regards, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 02, 2010, 01:55:42 PM
Hey Brian
are you using trsfos on inputs,or line cards?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on May 02, 2010, 02:04:17 PM
Did you slug the switch to give you some sort of voltage drop when in the center position? This is possibly being handled in PT or ITB some way. Maybe you don't need this.

What I did, was to put the 47k in back of the assign switch, so if it's assigned left it goes through one 47k, if right the other, and if center it hits both (and of course goes both ways).  I compared that to the way that PT handles assigning a signal hard side vs. center and it's almost exactly the same as far as level coming out.  Seems to work well.  Also if I for instance have one center and one left, I get the correct levels out the other side - I was worried about crosstalk, but this setup seems to address it well.

Also, if I have both channels center (or to the same side) and sum them it seems to have a very similar action to PT wrt to gain.  I should redo my tests and document the results.

So, 4 Inverting ACA boards and a single 2-ACA-Bo card is 20 discrete opamps. Typically, a 2520 style amp will draw around 22-25mA when idle and around 50-52mA when driving a 600 ohm load. That's per rail. That has been my experience anyways. So worst case you will draw 52mA times 20 DOA's is 1040mA or just over 1A. I would gather any supply that will give you 1.2-1.5A will be fine. Actually, the DOA's on the Inverting ACA cards will never draw that much as they have a very small load. You may not find a dedicated 2 rail, bipolar PSU project around. There may be one but I don't recall seeing it. Not to pimp but you could always get a 51x PSU PCB and only build out 2 of the rails. Leave the rest of it unpopulated. Maybe someday in the future you could build out the other main bipolar rails for +/-16V or whatever. Same with the 48V section. Just don't build it. Just a thought.

Pimp away! I actually have a 51x PSU built however it's going to power my 51x chassis.. if only someone could come up with some of those custom transformers :)

But seriously, that's not a bad thought.  Chances are that I'll end up going down that road since I think you're right, a dedicated 2 rail PSU project doesn't seem to exist.  I had considered making my own board and just umm.. borrowing 2 rails from one of the other projects.  I may not be a good PSU designer but I'm an excellent copier!  It's just kind of an expensive way to go.

And thanks for the advice on the total expected draw.  That would have been my next question.

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on May 02, 2010, 02:07:57 PM
Hey Brian
are you using trsfos on inputs,or line cards?

Neither, actually.  To keep things simple, I simply floated the lo on my balanced inputs.  I know that this won't work for everyone, but it's just fine for my application.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 02, 2010, 02:20:39 PM
I myself see nothing wrong with this especially if you don't have really long cable runs. PRR has said many times around here that there is nothing wrong with unbalanced cable runs in a studio.

FWIW, the majority of the connections in my console are unbalanced. Maybe they did not have the same concerns back then with interference but my desk is pretty damned quiet, even now. Anyone who has built the 2-ACA-Bo knows that it is unbalanced busing. I know that balanced busing was one of the things that Paul Wolff introduced when he took over API.

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 02, 2010, 02:39:30 PM
The inputs will get a +4 balanced sig from a pro t, Brian have you seen how dangerous 2 bus does the switch? It's all stereo pairs and when you hit the switch it's 2 monos(for kick sn bass center voc)
So one bank of 8 would be all you need for mono switch 4 swt = 8 monos..
I want 24 because the more chs you sum out the better the results..
I am still not clear on how many ins per doa , the diagram show 8 ch per ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on May 02, 2010, 02:43:57 PM
I myself see nothing wrong with this especially if you don't have really long cable runs. PRR has said many times around here that there is nothing wrong with unbalanced cable runs in a studio.

FWIW, the majority of the connections in my console are unbalanced. Maybe they did not have the same concerns back then with interference but my desk is pretty damned quiet, even now. Anyone who has built the 2-ACA-Bo knows that it is unbalanced busing. I know that balanced busing was one of the things that Paul Wolff introduced when he took over API.

Best, Jeff

Oh, I definitely agree.  If I have 50' of cable from a mic to a board it's a different matter but I certainly feel comfortable with the noise level in my contained little environment here which is FAR smaller than your desk.  I guess the only thing to do is to take some measurements when it's all together.  We'll see.

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on May 02, 2010, 02:57:06 PM
The inputs will get a +4 balanced sig from a pro t, Brian have you seen how dangerous 2 bus does the switch? It's all stereo pairs and when you hit the switch it's 2 monos(for kick sn bass center voc)
So one bank of 8 would be all you need for mono switch 4 swt = 8 monos..
I want 24 because the more chs you sum out the better the results..
I am still not clear on how many ins per doa , the diagram show 8 ch per ?

Yes, I had a look around at the different channel assigning mechanisms and I wanted to build something as flexible as possible, so I made every single channel assignable L-C-R.  The way Dangerous does it is probably fine for just about everything you might need to do.. look at your mixes and see what you might require.

And yes, I will have a maximum of 8 ch per DOA - 16 L and 16 R per 4-ACA board.  So if you don't want to exceed that number, you could have a total of 64 L and 64 R (4 boards of 4-ACA) bussed into the 2-ACA-Bo.  Thus, my question regarding sizing the PSU.  I'm sure these aren't hard limits, but it's the way I'm putting it together and will be FAR more than I'll ever really need (famous last words!).

Once I get the whole thing cobbled together in the next week or so, I'll be happy share what I did.

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 02, 2010, 03:04:25 PM
That diagram was basically for my own mods and use. Sure anyone can use it though. The 2 mix on my console, which is essentially a single 2-ACA-Bo card, was summing 32 input channels plus 4 echos with no problems. I decided to add the sub-summing Inverting ACA boards since I am now also summing the 32 monitor inputs and those echos to one stereo mix bus. Now I am up to 72 channels at the 2-mix. I had read about the massive O'Henry API console designed and built by Harold Kilianski. Steve Firlotte also did some work on this huge board. In one of my few conversations with Steve, he told me they employed "bucket summing" much like Neve and SSL. They have some 88 inputs at mix. The Inv-ACA was my API like solution to "bucket summing".

Cool O'Henry Mix article (http://mixonline.com/mag/audio_ohenry_sound_studios/)

Dale Manquen article on O'Henry's API (http://www.manquen.net/audio/index.php?page=12)

Very interesting stuff, IMHO.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 02, 2010, 03:19:35 PM
Yeah the cable runs it most cases be short, mine will be about two ft interface to mixer, but i am wondering if the transfo or line card input is where the fatness comes from,like you said in another post Jeff, running though the API sounds like a record..
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 02, 2010, 04:00:52 PM
Yes, this is a big part of the API all discrete signal path.

For a typical line input to 2-mix on my console, it goes something like this:

-2520 balanced receiver DOA on input channel (DOA count: 1)
-2623-1 x-fo balances input channel's 1st stage output or "send" (X-fo count: 1)
-2 2520's on typical 500 slot eq (DOA count: 3)
-2503 x-fo balances output of eq (X-fo count: 2)
-2520 post fader booster of input channel (DOA count: 4)
-2520 on my Inv-ACA (DOA count: 5)
-2520 on 2-Mix ACA (DOA count: 6)
-2623-4 x-fo balances output of ACA (X-fo count: 3)
-2520 on 325 post 2-Mix fader booster (DOA count: 7)
-2503 x-fo balances output of 325 booster (X-fo count: 4)

So, that's 7 discrete opamps and 4 transformers. Granted, it takes a lot more than this to "make a record" like a great song, great artist and a great performance but, it is definitely a mixing signal chain that is hard to beat.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 02, 2010, 09:38:12 PM
Hey Jeff
could I use your 4ch aca cards for the line inputs, by changing a few caps & resrs
the 325 line card looks real close,that would make it complete..
Line doa to aca to booster= fatness??
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on May 03, 2010, 04:29:38 AM
The answer to that would be yes. I am doing the same thing. A few trace cuts and careful mounting of components without a thru-hole. That should work fine. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: SIXTYNINER on May 03, 2010, 07:00:44 AM
HEY Jeff
do you mean the "porn" console in the picture attached?

That diagram was basically for my own mods and use. Sure anyone can use it though. The 2 mix on my console, which is essentially a single 2-ACA-Bo card, was summing 32 input channels plus 4 echos with no problems. I decided to add the sub-summing Inverting ACA boards since I am now also summing the 32 monitor inputs and those echos to one stereo mix bus. Now I am up to 72 channels at the 2-mix. I had read about the massive O'Henry API console designed and built by Harold Kilianski. Steve Firlotte also did some work on this huge board. In one of my few conversations with Steve, he told me they employed "bucket summing" much like Neve and SSL. They have some 88 inputs at mix. The Inv-ACA was my API like solution to "bucket summing".

Cool O'Henry Mix article (http://mixonline.com/mag/audio_ohenry_sound_studios/)

Dale Manquen article on O'Henry's API (http://www.manquen.net/audio/index.php?page=12)

Very interesting stuff, IMHO.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 03, 2010, 11:01:34 PM
I think I have to follow your lead on this Tubemooly, I am to much of a newb...

What's your plan on pwr supply?
The x51 may work with a bigger transfo,
with 24 ch I will have about 32 doa's in mine..
I had a vintage Amek that had a big supply so I am somewhat fimilar with console supplies.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on May 04, 2010, 04:38:29 PM
Jeff : I have 2 modules 528, 1 is a vintage ,circa 1972 , and the other is the datatronix era that you've saw in the pictures . The datatronix one has a different 2622 footprint, the room is for a jensen JE 6110K-A PC . And that footprint is the same as the ED's xfmr . Following the tracks it's seems that there's a little mod on them. the way that the pad switch is connected , and there's an R 5 that it isn't on the schematics that us have.( try to find R5 on yours).i will post you a pict tomorrow, now is too late.
regards.
pedro.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: PATAPETER on May 05, 2010, 04:05:53 PM
here the picts: see the bottom switch tracks.they are different. and R5 is with R34 and on the other leg to gnd.
(http://img22.imageshack.us/img22/6504/img0100w.jpg)
(http://img192.imageshack.us/img192/3074/img0098ml.jpg)
(http://img291.imageshack.us/img291/2521/img0096w.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on May 06, 2010, 04:19:31 AM
I think I have to follow your lead on this Tubemooly, I am to much of a newb...

What's your plan on pwr supply?
The x51 may work with a bigger transfo,
with 24 ch I will have about 32 doa's in mine..
I had a vintage Amek that had a big supply so I am somewhat fimilar with console supplies.

Johndcx - Where are you located? If I can't just purchase an off-the-shelf linear power supply (such as Power-One), then I build one. I believe you are correct that the 51x power supply board will handle more current than it's designed for now using the standard build. But we should confirm that. I'm working on a discrete mixer of my own (slowly). It's going to be line input only. I don't need mic pre's for this mixer. It will have 16 input channels and then 8 FX returns mixing down to a stereo bus. I have most of the chassis hogged out and six or seven of Jeff's boards mounted in there and a bunch of transformers mounted too. I've been a little bogged down figuring out / getting / building all the pushbutton switches for the routing and such. I need 5 DPDT switches per channel. I can't remember what all 5 are needed for right now. I will dig out my notes. So getting these switches figured out and mounted in my chassis has bogged me down considerably for a few months. But I think I have that figured now. Send me an e-mail at tubemooley_at_yahoo.com and I can forward you a few photo's if you want. I'm more concerned with helping answer your questions on power requirements for your project. Do you plan to use DOA's which run off of +/-16vdc or DOA's which run off of +/-24vdc? Or both? Let's get a few parameters laid out here and then we can do some figuring. DANA.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on May 06, 2010, 05:19:35 AM
Yeah Jeff said the 51 power can be modded up and just built with the + - rails,
at this point iam not sure what v I 'll run at..
I thinking of doa's on the lines (325  style) to aca to booster ,so with 24 ch I'll have about 36 doa's after control and headphone outs?
I may just keep this line only and do pres later,I am thinking of a descrete style Danger 2 bus,also with only 1 bank of 8 mono switches, all rest stereo pairs..
I d like to have some differant sounds on each bank of 8 chs,
by using differant Doas, maybe some trsfos,and maybe that neve line card that's around here...
My front panel will only be 8 mono switches and maybe signal LEDs and
master vols ..
I have to get a stereo pair going first, then go from there, I have a long way to go..and the woods are dark and deep...
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: herrmann on June 09, 2010, 02:08:19 PM
Hi
I'm testing my small mixer. Sound is clean, but I notice that the negative 2623 output is twice the positive. Is there any reason ?

Thanks

Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 09, 2010, 05:17:52 PM
How did you orientate the 2623-4?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: herrmann on June 09, 2010, 05:32:32 PM
The blue mark to the 1.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 10, 2010, 07:39:25 AM
The blue mark to the 1.

Yes, this is correct.

Funny enough, I have never made the same measurement as this, from Hi to gnd and from Lo to gnd. I have only measured between Hi and Lo, the normal way.

I checked one of my PCB builds and found similar results to yours. Not only on the ACA side but the 325 Booster side as well.

After some investigating, I see Bill Whitlock has written some things on this subject. This is quite normal I guess. If you do a Google search, you will find many interesting things from Bill on this, like this reprint here (http://sound.westhost.com/articles/balanced-2.htm). I guess there is a big to do regarding the myth of the balanced signal conductors having symmetrical voltages when having the same impedance is of much more importance. He has some nice info in chapter 32 of The Handbook For Sound Engineers too. To quote, "The idea that balanced interface is somehow defined by signal symmetry is simply wrong!".

It almost seems like this is a topic for a dedicated thread! A very interesting one indeed.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: herrmann on June 10, 2010, 09:00:30 AM
Quote
Funny enough, I have never made the same measurement as this, from Hi to gnd and from Lo to gnd.
Cause I only have one probe on my scope ! I have to get another one someday.

So this is not something to worry about. But in this case, we are loosing signal (and increase the noise floor) in the master fader, no ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 10, 2010, 09:59:22 AM
Should be no increase in noise as the impedance (not signal level) between each conductor to ground should be equal.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: edanderson on June 10, 2010, 03:12:26 PM
measuring on the secondary side of output transformers, you have to remember the that the hot and cold ends of the transformer are floating.  the signal is not relative to ground (as established inside your circuit or anywhere else) so if you measure with one meter lead to the hot end and one to ground, you could get just about any fraction of the nominal value.  this will change if you ground either end of the winding when you measure -- you could also ground the center tap, which would "force" the hot and cold ends to give you the results you expect.

so, this is not a problem, this is exactly what should happen...

ed
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on June 10, 2010, 04:35:08 PM
So, good progress is being made.  Fired up the whole thing today.  To pick up a previous topic, we were wondering about how much noise I'd wind up with if I float the Lo signal on my input.  The answer is some..

Just generally looking at peak levels on the meters in PT (I know not really accurate, but it's a good enough measure), I get:

Just 2-ACA-Bo             : -95db
2-ACA-Bo + 4-ACA       : -85db
Input cables hooked up : -65db

As I have it right now, the only path to ground for the audio on the input side is via the 100k on the input to the 4-ACA.  If I run that straight to the chassis, I wind up with about -70db.  That's better, but I still hear a very slight hum if I crank the output.  I guess maybe that's what I live with?  I'm not sure how else I could configure it.

Speaking of that 100k, one thing that I noticed in my checking of grounds is that the 100k on the input to the 2-ACA isn't really doing much.  On the front side, it's connected to the ground on the output of the 4-ACA, which goes to the chassis.  On the back, it's also connected to the chassis.  So in my configuration, that resistor is rendered ineffective.  Nothing to really worry about I would gather, but just a note around the way I'm using it here.

Bug hunting aside, the thing works great!  I'm really happy with how it all turned out.  Did a VERY quick mix on something here and I love it :)  Thanks Jeff for making all this available!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Johndcx on June 11, 2010, 02:56:58 AM
I wonder will I have better specs if I use the doa line in??
Those specs don't seem so good for a descrete mixer?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on June 11, 2010, 07:41:43 AM
No, it's not great.. yet :)  I'll keep on with the troubleshooting and I'm sure I'll get the noise down.  Maybe it's the cables?  Maybe it's the DA?  Maybe I missed something?  Don't know, but I'll get it sorted.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 12, 2010, 04:11:21 PM
Hey guys,

Been offline for a few days with computer "issues".

Anyhow, the 100K hanging on the non-inverting DOA input of the ACA portion of the card, is a dedicated ground reference resistor for the opamp, if I am not mistaken. With out this resistor, the base on the first input transistor in the 2520, will possibly not have any "bias reference". This depends upon how your ground is connected/brought to the ACA card. I believe API put this resistor there in case the input to the card had the shield or ground floating on one end. If the shield of the input cables was floating on the supply side, the DOA still had a ground reference thru this resistor. FWIW, the shield on the bus cables is about the only shield that is connected at both ends in my console. So, this 100K resistor is effectively useless for me too. But, may be critical for the next guy.

You could try physically floating the PCB so that the only ground connections are thru the Molex PSU connection. All of the mounting holes connect to the ground plane on the card. This is no issue for my console as the frame is all wood. If this helps, maybe nylon screws and standoffs will be a good solution?

The noise specs for a 2520 in this configuration are pretty damned respectable I think. Look at the info for Figure #3, Lossless combining Amplifier on the 2520 spec sheet (http://www.danalexanderaudio.com/ApiInfo/api2520_02.jpg).

I think there may be some other noise causes that need to be tracked down.

Keep us informed.  ;)

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on June 13, 2010, 12:15:45 PM
It's always the grounding!  I'm getting close, though.  Pretty sure I've isolated it to somewhere around the DB25 inputs or the cables to my DA.  I used some pretty cheap stuff there, so maybe I'm paying the price.  With no signal on the input, it's pretty darn close to the noise numbers in that spec sheet, so I know I'm in the ballpark!  I'll get it sorted, I'm sure.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on June 14, 2010, 11:29:37 AM
Jeff, a question for you.. You mention that your bus cables have the shield to ground on both ends.  Is the shield in those cases the actual audio ground?  As in, a single conductor cable using the shield to carry the ground.  In my case, I used a two conductor cable for each channel and have tried running the grounds in a number of different configurations, all with roughly the same effect.  The shields however, are connected to nothing on either end.  I figured the run was so short (maybe 12" ea) that it didn't matter.

I basically have the grounds from all 16 channels bussed together at the LCR assignment switches.  Kinda wondering if this is the wrong approach entirely.  You can see what I've done in the attached picture.  The two terminal blocks on the far left receive the ground for each channel and then you can see it bussed across the bottom to the outputs, which go to the 4-ACA.

It's funny, you can get everything working and then it's the audio-101 junk that trips you up!  I'm hoping that some fresh eyes will see something that I'm not.. one of those things where I need to not think about it for a few weeks and then come back to it and all of a sudden the problem is obvious.

(http://nehpc.com/LCR_back_sm.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on June 21, 2010, 02:06:11 PM
So yes, I do realize what an outstandingly stupid question I asked.  BUT, it did get me thinking more about the right things and I'm happy to say that with proper grounding of shields, fixing some bum cables, and some general sorting, I was able to significantly reduce the noise in the system to the point that I can't hear it at all with everything cranked.  Sounds good to me!  Or I guess, it doesn't sound and that's good for me :)

Final numbers here:

Just 2-ACA-Bo                         : -98db
2-ACA-Bo + 4-ACA + LCR board  : -95db
Input cables hooked up             : -85db

That extra 10db is entirely 60hz.. just a bit of a bump, and I think I could even chase that out although I'm not really too concerned.  This is 20db better than it was before!

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 21, 2010, 03:09:46 PM
Nice job Brian!  8)  Cool little bus board you got there too!  ;D

I remember when I had talked with Paul Wolff a few years ago about modding my desk and refurbing. One of the first things he told me was to replace the cables than run from the motherboard bus tracks to the ACA boards with "that nice, big Mogami instrument cable". This I did. It is some big sh*t which takes up lots of room in the desk. It has a very nice shield though which is important for this use I think.

Thanks for the positive updates.

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on July 06, 2010, 12:52:18 PM
Completed the build yesterday, took me a little while to get used to the API sound, as I'd never experienced it b4: silky top, upfront mids and tight bass.

About to drop it into a 1998 40 channel Trident-MTA console, summing in buckets of ten channels.

Was going to come off the consoles bipolar 18v supply, but suspect as it's the consoles largest configuration, the PSU is prolly flat out, so using an external bipolar 16v for the 2-buss.. any grounding tips or suggestions are very welcome?

Thanks goes out to Jeff for a a great project.

(http://i44.photobucket.com/albums/f23/sin-tech/BigBoys2Buss.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on July 06, 2010, 02:55:52 PM
Sintech,

Looks like you had as much fun building DOAs as I did!  Although, I only did 8.. gets a bit tedious, I'd say.

At any rate, it took me quite some time to get the grounding sorted.  In the end, it wasn't anything too fancy.  Basically, I did a star ground with the sig input ground, PEM, and PSU.  The sig ground does kind of a trip around the chassis though before it gets there and I think that could be improved.  Things that didn't seem to make a difference were floating the PCBs or allowing them to ground to the chassis via their mounting holes, and the sig ground on the output (I have that to the GND at the output from the BO).

Regarding shields, Jeff mentions that in his console the bus cable shields are grounded both ends.  I kinda did that.  The inputs to my bus board (a few posts up) are grounded just one end but the shorties from the output of that to the 4-ACA are grounded both.  Seems to improve me a few DB.  I really just had to play with this part a little to see what would get me the best results.

I think my biggest noise problem on mine still is the float Lo scenario on my inputs from a balanced source.  I'm currently breadboarding an input section with 5532s to see how that works.  This thing is turning into a bit of a playground for me to try things.  Bound to wind up with the most unnecessarily overbuilt summer around :)

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gar381 on July 06, 2010, 07:09:52 PM


(http://i44.photobucket.com/albums/f23/sin-tech/BigBoys2Buss.jpg)

VERY NICE!! Sintech


GARY
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on July 07, 2010, 05:22:46 AM
Quick lash up in context, got a feeling the Trident-Mta channel into the API 2 buss is going to be a killer combo.

Real world test, the 47k summing resistor effects the pan law, as the  summing for the 24 groups are staying stock, reverted back to the 22k summing resistor.

The correct pan law is now back, and it sounds cool, as in it doesn't sound badly wrong... the ACA feedback resistor and cap are calculated for the 47k.

What would be the best method to check and adjust this?


(http://i44.photobucket.com/albums/f23/sin-tech/MTAtest.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 07, 2010, 08:35:37 AM
You will probably want to go with a 22K feedback R then as well. You can play around with this to make sure the gain staging is how you want it. This will probably also require a slight tweak on the feedback cap.

You can use Bicycle Bob's handy little calculator to figure your -3db frequency knee. www.bicyclerecordings.com/various/gainchart.xls (http://www.bicyclerecordings.com/various/gainchart.xls)

Just enter 22000 (or whatever value you end up with) into the Rf box and adjust Cf to a common value. I would gather 68pf or 82pf would be a good value. Typically, from what I have seen, API was between 65K and 105K with that -3db point.

For instance, the original 312 pre was 20K and 120pf. The console pre (VP26) is 20K and 82pf.

Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on July 07, 2010, 10:11:28 AM
Thanks Jeff, so.. I change just the feedback resistors in the inverting ACA to 22k, then leave the 2-ACA-BO the same? as they're fed with 47k's from the outputs of the Inv-Aca.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 07, 2010, 10:14:00 AM
Yes. That should be a solid starting point at the worst. Should be fine though.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Tubemooley on July 07, 2010, 01:05:47 PM
Veddy interesting developments. Ya' know..... I've been wondering about that 100k resistor on the inverting input of the ACA (I think it's the inverting input; I'm working from memory here). Not to be a dick..... but this reinforces once again how very, very important grounding is. Basically, ya' never connect both ends of a cable shield. Never. But it still gets done occasionally (under certain circumstances). I need to remember to add these new posts to my ACA notes file. Nice work Sintech. Really nice work. DW.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: myker on July 23, 2010, 10:25:46 PM
hi guys, so from what jeff is saying i should be able to sum 16 channust floels from my 192 i/o with just one 2-ACA-Bo? by jating pin 3 and splitting channels with 47k resistors into the ACA side? then route that signal to the 2 gang pot and into the booster amp and monitor/talkback etc.? then i could run the r and l signal back into the 192 and print it? as well as monitor that signal im listening to as well?
sorry if this doesnt make sense
-mike
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on July 27, 2010, 03:17:25 PM
Connecting more channels today, I'm noticing ground issues going into the Inverting ACA's,.

I'm taking the channels earth and the signal after the summing resistor (either left or right) down a screened lead, in to the + and common inputs, all is ok for the first 10 channels.

I then switch to the next ACA input.... and hummm!!! But.. if I remove the common leaving it floating all is good, and the channel 11 is fine also running just with the positive in place.

I'm wondering what's the correct scheme? I'm doing 40 channels in buckets of 10.

(http://i44.photobucket.com/albums/f23/sin-tech/Summing.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 27, 2010, 03:47:47 PM
Wow! That is looking killer!

I can tell you what I know from my board. For almost all the cable runs, API would only connect the screen on one end. I would try floating the screen at the source (channels) and only connecting it at the destination (ACA). The ACA boards are probably getting a ground reference from your 3 wire PSU lines right? I can't really tell form the pics. My bus cables have the screen connected at each end but, I think it all plays into the over ground scheme of the desk. Only connecting at one end should be fine. That is why there is the 100K reference R on the non-inverting DOA input of the ACA. Someone mentioned a while back about removing it. That would not be good in this case. You do have the PSU ground connected with the bipolar supply voltages?

Lot's of work there, no doubt!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on July 28, 2010, 04:54:03 AM
It's getting a lot better for some fooling :-)

I'm using a second power supply for the ACA's, so..  the API ground is connected to it's bipolar supply ground and also the consoles star earth. Without the star earth connection it's hum city.

Can hear a faint mains hum, should I float the ACA supplies center tap and leave it just connected to the console star earth?.. I've been a bit nervous to try this!! heheh
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on July 29, 2010, 07:17:21 PM
Sintech, looks really cool!

I've found that fooling about with it in different ways has shown me a lot.  I'm getting REALLY close to dead quiet on mine.

Since the last time, I've made an input/bus board.  I proto'ed a version using 5532 op amps, but elected to go with THAT 1200.  It works really well!  It's SO much better since I don't float the Lo input anymore, and have a good way to round up and deal with the grounds.  Also, I'm not running cables all around hell and back to assign LCR via switches, but rather doing it with relays on the board.  I'm rather proud of this part, being the relative noob that I am :)

I actually found that some portion of my noise is coming from the Bo section.  If I go direct out from the 2-ACA, it's much quieter.. actually near to the level of the whole unit just being unplugged.  There's just a bit of hum left, which I'm thinking is in my power supply - not sure how to fix that.  I may actually just leave it this way since without the booster I'm actually at unity, which is all I really need in my application.  I had mine set up so that we get -6 from the 2-ACA to BO (I think - it's grounding the lo output from the 2-ACA as per Jeff's schemo) and then the BO was just making that 6db back up again.  No fader involved.

Although, I'd really like to tear apart the BO and see why it's noisy, just because it's bugging me!

So, my ground scheme looks like this:

input sig gnd -> star ground
input/bus board to 4-ACA -> shields grounded to at output from input board only, not at ACA
4-ACA to 2-ACA -> shields grounded at output from 4-ACA only
2-ACA to Bo -> shield+lo to ground at input side of Bo
Bo to XLR -> shields grounded at output side of Bo

Actually, as I write that all down, I notice that at the Bo is the only place where I ground the shields at the input side, rather than the output side.  I guess it helps to say it out loud!  I'll give a shot the other way 'round.

So, so close :)

Let me know what you end up with, Sintech.  I'd love to compare notes.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 16, 2010, 11:35:11 AM
Hey guys,

Just reading all of this info and I'd like to start up by building a 4 Channel Inverting ACA and a 2 Channel ACA & Booster, and start with only 2 or 4 line inputs.

I was hoping to use Martin's EZ1272 line input boards for the input channels, but the panning and the connection from the output of those into the inverting ACA is what confuses me.  Can someone fill me in a bit on this?

Thanks!
Sig
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 16, 2010, 10:38:51 PM
Jeff, a question for you.. You mention that your bus cables have the shield to ground on both ends.  Is the shield in those cases the actual audio ground?  As in, a single conductor cable using the shield to carry the ground.  In my case, I used a two conductor cable for each channel and have tried running the grounds in a number of different configurations, all with roughly the same effect.  The shields however, are connected to nothing on either end.  I figured the run was so short (maybe 12" ea) that it didn't matter.

I basically have the grounds from all 16 channels bussed together at the LCR assignment switches.  Kinda wondering if this is the wrong approach entirely.  You can see what I've done in the attached picture.  The two terminal blocks on the far left receive the ground for each channel and then you can see it bussed across the bottom to the outputs, which go to the 4-ACA.

It's funny, you can get everything working and then it's the audio-101 junk that trips you up!  I'm hoping that some fresh eyes will see something that I'm not.. one of those things where I need to not think about it for a few weeks and then come back to it and all of a sudden the problem is obvious.

(http://nehpc.com/LCR_back_sm.jpg)

What is this board, and how do I get one...?

Thanks!
Sig
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: horvitz on August 16, 2010, 11:19:07 PM
What is this board, and how do I get one...?

You don't want one!  Although if you're dying for a marginally useless piece of board, I have two extras that I'll be happy to send you for the postage.  Then you can throw them away instead of me.

I'm not familiar with Martin's input board, but it sounds like if it's got a L and R output for each channel, just strap a 47k on each of those, and then bus 8 of each into the 4-ACA inputs.  If you look at my crappy bus board, you can certainly see where it does just that - 8 on the top, 8 on the bottom, and each can be assigned L, R, or both, where they go through a 47k and then bussed out to the right.

  Brian
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 17, 2010, 12:05:03 AM
I think it's just too late for my brain to process anything...

Martin's boards are just line input boards, so they only have a balanced mono out, not L or R...

So you're suggesting that your board is unnecessary?  I am just not understanding at all how or where I would place a pan pot after the (channel ie. line input board), and how that signal would get to the ACA board. 

Please someone help me understand how this all comes together...

Thanks!
Sig
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 17, 2010, 07:11:24 AM
Sig,

I am not sure how Neve use to do it but, if you take an unbalanced signal from Martin's line boards to a dual 10k linear pot, slugged with a couple of 2.2K R's(season to taste for -dB point when at center), connect each wiper to a 47K bus R, then connected all the bus R's to the inputs of the ACA, keeping Left and Right separate. That is pretty much it.

best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 17, 2010, 07:41:37 AM
Ok, so I should NOT be using the Neve line output transformer then?  Too bad, since it's a big part of the sound...would this still work if I did balance it?

Can you please explain what "slugged" means...I've not heard this term before.

There isn't a simple drawing someone has for all the connections, is there?

Sorry, just trying to get this all to make sense.

Thanks!!
Sig
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 17, 2010, 07:55:47 AM
Sig,

Maybe some of the Neve experts would chime in on where to take the signal that you send to the pan pots. API does did it before the output tranny. The output tranny was for Channel Direct Out only, not for the panned-bused signal.

Here is a post with some details on what I have done. I also see some Geoff Tanner and New York Dave info that I found.

http://www.groupdiy.com/index.php?topic=33007.msg402242#msg402242

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 20, 2010, 03:24:38 PM
Thanks for the info!

Is anyone using these relay boards to handle mute (or perhaps even solo?) in their homebrew consoles?

http://classicapi.com/catalog/product_info.php?cPath=102&products_id=195

Wondering if I should pick up a bunch, and how exactly they would be wired up.

Thanks!
Sig
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Siegfried Meier on August 25, 2010, 07:06:33 PM
Thanks for the info!

Is anyone using these relay boards to handle mute (or perhaps even solo?) in their homebrew consoles?

http://classicapi.com/catalog/product_info.php?cPath=102&products_id=195

Wondering if I should pick up a bunch, and how exactly they would be wired up.

Thanks!
Sig

Anyone know?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 25, 2010, 10:32:25 PM
Sig ,

Check this thread out. I posted the skiz for the relay board there a while back. You will find much helpful info from others there as well.

http://www.groupdiy.com/index.php?topic=38094.0 (http://www.groupdiy.com/index.php?topic=38094.0)

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: haima on August 25, 2010, 11:58:10 PM
it's possible to use the one relay per channel for both mute and solo - solo is just "enable mute on all other channels that don't have solo depressed"...

that's how the JLM PM2000 solo in place mod works - it works well on my board. you'll need a "solo bus" etc might take some thinking and legwork.

Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 06:18:48 AM
Hi Jeff !
i'm planning to buy the 2-ACA boards to upgrade my tascam M3500,
and i need to evaluate the costs,
are the 4 transformers needed or can i build the 2-ACA with 4 opamps
and only the 2 2503 ?
As my inserts are unbalanced, i thought it's possible not to use the 2623-4,
is it correct ?
best regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 12, 2010, 09:33:28 AM
Hi Jeff !
i'm planning to buy the 2-ACA boards to upgrade my tascam M3500,
and i need to evaluate the costs,
are the 4 transformers needed or can i build the 2-ACA with 4 opamps
and only the 2 2503 ?
As my inserts are unbalanced, i thought it's possible not to use the 2623-4,
is it correct ?
best regards,
francois

Francois,

Yes, you can build it without the 2623-4's. The only issue you have is that the signal will need to be flipped 180 degrees again. The 2520's in the ACA stage are inverting. This inverting back is typically done with the 2623-4 transformers.

The 2503's could also be replaced with 2623-1's to save a little money. That was the config on the 2488.

IMHO, part of the color/sound of the entire circuit is from the 2623-4's. You will be eliminating some of the API color by not using the 2623-4's. Just a thought...

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 09:47:39 AM
ok,
now i understand that the 2623-4 not only balance the signal before the fader
but also flip phase after the inverting amps,
Ok i will save a few more bucks and order the whole things.
As i would like to order all parts at once from your shop
(BC/vishay eletrolytic caps etc... )
How do you proceed for sending the BOM for 2-ACA ?
regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 12, 2010, 09:53:29 AM
Typically when I ship I send them so I don't forget. The only other things that I have for this build on hand are the DOA sockets and the (4) BC 470uF caps. The rest is pretty simple stuff.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 01:16:45 PM
ok perfect,
DOA sockets and the 4 BC caps
thank you very much jeff !
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 12, 2010, 01:28:19 PM
...thank you very much jeff !
;)  :)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 01:31:33 PM
I also noticed on the pics that there are others BC white axial caps,
do you sell them ?
regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 12, 2010, 01:36:46 PM
Yes, a pair of 10uF/25V and also a pair of 220uF/16V. I don't carry those at the store. You will find that they are expensive. Make sure you get the 138 series.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 01:49:40 PM
ok nice !
i know mouser carries them but they're pricey,
if i remember correctly, you're cheaper than mouser !!!  :D
thnaks for these info jeff,
i think i will order the PCB,2623'S,L-brackets and caps today,
can't wait to install the ACA on my tascam, i hope it will boost my mixes !!!!!!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 12, 2010, 01:56:11 PM
order just made for half of the kit,
please send me the BOM soon !!!!!!!!!!!  ;)
thank you very much for all these amazing projects jeff ,
need to find some work and money totest your new VP312DI !
best regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: sintech on September 12, 2010, 02:20:55 PM
Progress report:

First mix today, for the 40 channel Trident MTA with Classic 2bus summing in buckets of ten, having spent the last three week installing into my studio space.

And the results are very pleasing indeed, massive headroom, infinite punch, great solid tone, no smear, it's a Big Boys 2-bus for sure.

Worth every penny spent., and would highly recommend it as the best way to bring a mid range console to life.  Massive thanks to Jeff :)

Scored a nice 200 segment plasma for the 2 buss metering.. schweeet :)

(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7900.jpg)

(http://i44.photobucket.com/albums/f23/sin-tech/IMG_7893.jpg)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: haima on September 12, 2010, 11:21:01 PM
the new board is looking (and apparently sounding!) great!  8)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 13, 2010, 10:40:39 AM
Hi Guys,
while looking at the 2-ACA block diagram,
and reading this thread,
i noticed that the insert points are before the fader,
On my tascam M3500, the fader and summing amps are before the insert points,
wich are unbalanced,and the insert return goes to the balancing boards,
mayeb i'm studid but someone explain me
the benefit of having the inserts before the fader ?
best regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: hobiesound on September 13, 2010, 10:59:13 AM
Hi Guys,
while looking at the 2-ACA block diagram,
and reading this thread,
i noticed that the insert points are before the fader,
On my tascam M3500, the fader and summing amps are before the insert points,
wich are unbalanced,and the insert return goes to the balancing boards,
mayeb i'm studid but someone explain me
the benefit of having the inserts before the fader ?
best regards,
francois


that way you can fade out your mix without messing up the threshold on your buss compressor.

as far as i know that's normal on every mixing desk....

greetings,

Thomas

Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 13, 2010, 02:42:01 PM
ok,
nice answer,
so my Tascam M3500 might not be a decent mixer..... ::)
hope to receive my 2-ACA soon !!
thanks for your reply,
best regards,
Francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 22, 2010, 11:53:19 AM
Hi guys
i have received my 2-ACA,
i am now trying to install it in my tascam M3500,
i've read and read the thread and studied schematics,
But i have a problem with the summing resistor,
All the summing resistors in my tascam are 22K ,
so after reading the thread,
i guessed i have to changed the summing resistors on the 2-ACA
to 22K and adjust capacitor to achieve same cutoff frenquencies
according to the gainchart xls file linked in the thread,
i'm not sure to understand if i need to add a 22K resistor before the ACA input
or if i need to change R2, R7 and C2,C6 on the 2-ACA pcb,
Any help would be greatly appreciated,
here are some links to the M3500 schematics:
http://img512.imageshack.us/i/tascamsummingamp.jpg/
http://img4.imageshack.us/i/tascaminputa.jpg/
http://img299.imageshack.us/i/tascaminputb.jpg/
http://img825.imageshack.us/i/tascambalancedpcb.jpg/

Hope someone could help,
Francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 22, 2010, 12:43:17 PM
Francois,

I would start with changing R10 and R15 to 22K. Also, C11 and C15 should be changed to 100pF or maybe 82pF. It is just the feedback components of the ACA that you will change.

Cheers, Jeff

Edit: see two post below for correct values.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 22, 2010, 01:59:01 PM
ok cool,
thanks for the reply,
so i guessed it's R10 and R13 not R15,
from 28K to 22K and i will change caps to 100pf,
i was also curious about the mult output on the ACA ,
what did you used it for ?
Regards,
francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 22, 2010, 02:19:41 PM
ok cool,
thanks for the reply,
so i guessed it's R10 and R13 not R15,
from 28K to 22K and i will change caps to 100pf,
i was also curious about the mult output on the ACA ,
what did you used it for ?
Regards,
francois

Wait, hold on a second! I spoke too soon earlier. I just dbl checked the schematic. I should never fully trust the memory anymore.  :-[ I would recommend changing R10 and R13 from 28K to 13K. C11 and C15 from 47pF to 100pF. The values on the schematic give you a -3dB knee @ 121K and the new values will be 122K (for feedback). Close enough I think! The original gain structure is -2dB after the ACA section. The 13K should give you that with 22K bus R's.

I do not use the mults after the ACA for anything myself. It was easy to add so I did. The mult from the Booster section can be used for a control feed or what have you.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 23, 2010, 12:45:16 PM
Ok jeff thanks for your reply,
unfortunatly i don't have 100pF neither 13K available,
I have 56pF and 200 pF and a 10K,12K 15K etc resistors,
I can use the gainchart calculator form bob schwenkler
to achieve same cutoff frequency,
but i don't know how to calculate the interaction with my 22k summing resistors
to achieve -2dB level,
can you explain me a bit or help finding the correct combination ?
best regards,
Francois
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 23, 2010, 01:05:33 PM
See figure #3 here. http://danalexanderaudio.com/ApiInfo/api2520_02.jpg (http://danalexanderaudio.com/ApiInfo/api2520_02.jpg)

Original Rf is 28K and Rs was 47K. Just make sure the end result is the same. Then use Bob's calculator like you say.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 23, 2010, 01:46:17 PM
thanks for the link,
so the formula is gain=Rf:Rs
and with Rf 28K and Rs 47K the result is 0,6 or -0,6 right ?
so as the tascam summing resistors are 22K
i'm stuck with the 13K resistor to achive same gain
right ?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 23, 2010, 02:02:19 PM
thanks for the link,
so the formula is gain=Rf:Rs
and with Rf 28K and Rs 47K the result is 0,6 or -0,6 right ?
so as the tascam summing resistors are 22K
i'm stuck with the 13K resistor to achive same gain
right ?

Yes, correct. Time to place an order at your local electronics supply house.  :)

I'm sure you could temporarily get by with a 12K to just get her going.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: pacemaker on September 23, 2010, 02:22:59 PM
yeah............
but my local electronic shop only have crappy ceramic disc cap,
and i'm not sure to find 1% metal film,
Time for a mouser order ! ;-)
Thanks for the great support !
i'll keep you informed and post pics in the thread
best regards
francois

Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 23, 2010, 02:49:15 PM
...Thanks for the great support !
Haha! It's only good if it works!  :D  Otherwise...crappy support!  :o

BTW, any C0G would be fine for the feedback cap.

Let us know how things go!

Cheers, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: wolfgang on September 23, 2010, 04:40:14 PM
12kfor Rf should not be a problem! Difference to 13k is only about 0.7 dB!!!


regards,
Wolfgang
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gar381 on October 07, 2010, 04:18:59 AM
Hi Guys

I needed a Classicapi 2-ACA for this nice old late 70s 8 channel Tangent 802a
to make a nice old school small GREAT sounding remote mixer out of this old
war horse. (interesting and fun project)

(http://gar381interests.com/Tan_front72.jpg)

The Classicapi 2-ACA PCB was physically to BIG to fit in the space
so I modded a Classicapi JLS Inv-ACA PCB into a 2-ACA
buy doing some creative mods with a little help from Jeff...
(THANKS my friend) to the JLS PCB and using
4--  2623-1-CF trafos.

(http://gar381interests.com/Tan_PBC_Tight72.jpg)
(http://gar381interests.com/Tan_PCB_2_72.jpg)
(http://gar381interests.com/Tan_PCB_3_72.jpg)

I added some P&G 8000 series faders , 10 - Barnett Ind.
7 LED VU meters and changed lots of caps and opamps.

This $50 ebone mixer now sounds like a $5000 mixer..... GREAT!!!! :) :) :)

BTW..Rs for this mixer = 10k
        I used for Rf  6.2k
        and Cf 150pf

I'll post a thread in the next few days in the lab on all the FUN :)
I had Modding this old BAR board.  I am VERY pleased with the
results.

GARY








Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 07, 2010, 07:36:32 AM
Nice work Gary! She is a sexy looking old gal indeed.  :o
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Benny on October 10, 2010, 11:40:50 AM
I'm doing the first listening test right now. 8 tracks of drums line out straight into 2-ACA-Bo. It worked from first power-up and sounds GREAT. Time to order more D-Sub connectors!!!

Benjamin
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: brennyb on October 26, 2010, 11:31:19 PM
this is all exciting,
2 Doa's built and 2 to go,
glad to see people enjoying, and great support here...
keep it up,

Brendan   :o
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: 0dbfs on November 16, 2010, 12:13:00 PM
Question:

Can I fit 2 ACA-OBO's into 1RU for four bus masters sort of like a 7800 form factor?

Thx,
J
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on November 16, 2010, 07:52:59 PM
Question:

Can I fit 2 ACA-OBO's into 1RU for four bus masters sort of like a 7800 form factor?

Thx,
J
The PC mount 2623-4's would be very close after some standoffs are used under the board. The vertical 2503's will never make it. I would suggest just mounting the iron off the board and flat. I would do this will all 4 transformers and use 2623-1's instead of 2623-4's. Then...no problem with everything fitting.

Best, Jeff
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: rrs on November 18, 2010, 01:42:34 AM
Hi Jeff

I am wanting to build a 14:2 channel mixer in which all channels can pan either Hard Left, Center or Hard Right.

Can I use these boards to do this and how would it be done.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JBVries on December 12, 2010, 12:08:16 PM


So, a DIY, all modular, vintage API style mixer. This is so do-able, and ultimately my goal.



I'm just starting to thumb through this thread, but I like the sound of that  :) Sooo many avenues for complete signal path customization.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: haima on December 12, 2010, 07:48:52 PM
Hi Jeff

I am wanting to build a 14:2 channel mixer in which all channels can pan either Hard Left, Center or Hard Right.

Can I use these boards to do this and how would it be done.

Hey David - balanced or unbalanced?
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bluesbaz on February 21, 2011, 12:49:14 PM
I would like to use the aca as a stand alone summing system. I was thinking of summing 8 balanced channels at a time and hitting a transformer before going into the summing card and then to the aca stage. Is there anything I should be concerned with when doing this? Or should I just unbalance the inputs?
I have 8 1731 and 8 2520 waiting to test in this circuit..... Should be fun!
Thanks again!
-s
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bluesbaz on February 22, 2011, 06:25:40 PM
Nothing..... Really?
-s
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 22, 2011, 06:39:21 PM
Well, you could use Don's "Stereotype" boards and have a discrete front end to the summing. That may be more fun than a transformer. He did them in 8 channel units IIRC. It really depends on the device you are getting the balanced signals from as far as just unbalancing them. A simple unbalancing would be the most cost effective way to start. Either the low side to ground or float. If you have problems or are not happy, then maybe you could look at an alternative like Don's boards or maybe transformers.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: herrmann on February 23, 2011, 10:23:18 AM
Hi
I'm very happy with my 13/2 little mixer, I want to upgrade a bit, thinking of adding some busses, maybe aux. Can I do it with your 4 ACA board ? Adding on each a 2623 phase reversed=>balanced insert point=>pot=>47k=>2 ACA Bo board. One board for 4 independent busses.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 23, 2011, 10:27:37 AM
Yes, that should work.
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: funkmuffin on March 19, 2011, 08:26:15 PM
Hi Jeff -- I'm building my 2-aca-bo, and need to get the 2623-4's oriented correctly.  Is the blue dot on the transformer pin #1?  I'm assuming so, but it's easier to ask then to de-solder.  :)

Thanks!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 19, 2011, 08:30:05 PM
Hi Jeff -- I'm building my 2-aca-bo, and need to get the 2623-4's oriented correctly.  Is the blue dot on the transformer pin #1?  I'm assuming so, but it's easier to ask then to de-solder.  :)

Thanks!
Correct you are funkmuffin. Blue dot = pin #1.

Desoldering can be mighty enjoyable with the right tools  ;D  Don't underestimate it!
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: haima on March 19, 2011, 09:37:21 PM
Desoldering can be mighty enjoyable with the right tools  ;D  Don't underestimate it!

+1  :)
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Marcocet on March 20, 2011, 12:42:27 PM
Okay, I'm finally getting started on my headphone cue mixer project. The plan is essentially to build little 10 channel API mixers (8 mono 1 stereo) with built in headphone amps. I've really only got one question but I figured I should run the whole thing by some brains to see if I'm missing anything else.

The plan is to use one of Don's Stereotype boards per mixer. That should give me 8 mono inputs. Instead of the multi point pan I'm just going to use a LCR switch with 5k resistors. Then I'm planning to use an ACA/booster board. The boosters I'm going to use as input amps for the L and R stereo, matching the components to the stereotype boards and bypassing the transformer (also I think I need to reverse the input leads?). The aca will be the left and right summing amps (no master fader, I'm just planning to use the volume on the headphone amp as a master). These are gonna go directly to a Purple CANS headphone amp with no input transformers.

Anybody see any offhand flaws in this plan before I build a prototype? Also does anybody have a good source for 1k faders?

Thanks
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: rhythminmind on September 30, 2011, 06:40:05 PM
Title: Re: classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 02, 2011, 03:34:16 PM
Is the output of the ACA line level?
No, it is -2dB. You could adjust if this is the only stage you are gonna use.

Quote
It seems I can just take the ACA transformer output into an A/D, or do I need the booster?
Yes you can do this. Besides more DOA and x-fo goodness in the path, they are there to buffer the pgm mix fader and insert point. If you don't use these things, you could skip the booster section.

For the rest, you will have to experiment IMO. I have not used one in this way so can't say for certain what needs to be done.

Cheers, Jeff
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: piano on December 02, 2011, 09:16:46 PM
I am building a summing box.

I have a SUMTHING and the 2-ACA with DOA's coming. (I will order the extras which go with this.)

Besides the usual DB25, XLR connections is there anything I am missing?


Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: 3nity on December 18, 2011, 10:47:04 AM
Hi people.
I never been interested in summing stuff but since im working on my console.
do you guys think an Einstein would work well with the ACA??

Im pretty new about summing...

Thanks.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on December 18, 2011, 12:23:19 PM
3nity, I myself am not intimately familiar with the Amek Einstein. Are the program buses balanced or unbalanced? The old API summing is unbalanced. What are the bus R's? It almost doesn't matter as you can adjust the feedback R and C in the first ACA stage to accommodate. Many guys have done that and mentioned here on this thread.

Hope that helps. Jeff
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: tgauge on December 18, 2011, 07:56:51 PM
Hello Jeff,
I have two questions regarding the 2-ACA-BO...

1. Because the 2-ACA-BO is unbalanced and my proposed summing network will be balanced, would you suggest a) that I rework the plans for the summing network to be more compatible (i.e. de-balance every input as they enter the summing box), or b) sum balanced and then de-balance the output signal right before it goes to the 2-ACA-BO?  I'm assuming B would be best, easiest, and cheapest (saves a lot of money to de-balance 2 channels than 32) but I wanted to get your input on it before I started.

2. Do you have a mailing list or anything of the sort to notify your customers of when products arrive (i.e. the EA-2503)?  I was waiting on it to come in, and then I went back to the page and the date was pushed out.  I'm just checking, otherwise it is not problem to just back on the 2nd...

Thank you Jeff!  I'm really looking forward to this project!

-TG
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: brennyb on January 12, 2012, 05:52:52 PM
jeff just a quicky the 2aca board outputs are balanced, the booster channel inputs are unbalanced. To the bo channel do you drop the common and take the + from aca to the BO side as well as the - aca to the Bo side (connecting aca + output to + bo input & -ACA output to the C bo input)?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on January 12, 2012, 06:47:28 PM
Yes correct. If you look at the fader schemo in the support docs, that is basically what it show...minus the fader of course.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on January 24, 2012, 01:14:38 PM
Jeff, wow. I had no idea this was even out there until yesterday. Seems like it would be perfect for my Yamaha PM2000.

I attached a copy of the PM2000 schematics. If anyone is so inclined, I have a couple questions.

I'd like to be summing in total 32 input channels and 6 mono busses.
For the input channels, it appears I would just pick a pair of the existing program (main) buss sends and connect the input channels to the ACA after the main program buss bar.
My summing resistors appear to all be 33K.

For the other six busses in my console (second schematic) I think it would be easiest to take the signal right before it goes into the matrix amplifier. There is a switch right before the output transformer, which would be very convenient, and I don't really use the matrixes on the PM2K anyway.

Do you guys think this is a good approach? What would the adjustments need to be on the ACA to provide for the 33K bussing resistors if any?

This would be SO awesome. It would totally kill  2 birds with one stone in that it would allow me to finally sum my busses to the 2 mix without having to use the matrix amps (this is a strange peculiarity that Yamaha came up with) and also work around the non-discrete IC summing that's in the busses right now.

EDIT:Well, here's a word file w/ the schematics pasted on it. They were too big to upload the whole thing. If anyone wants to host a link, or just wants me to email them a copy of the full PM2K schemos I got 'em.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: brennyb on January 26, 2012, 08:35:53 AM
just a quick question, between the 2 aca channel and the booster should the 10k fader/pot be logarithmic rather than linear?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on January 26, 2012, 10:34:39 AM
just a quick question, between the 2 aca channel and the booster should the 10k fader/pot be logarithmic rather than linear?
Either will function but you will want log.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on January 29, 2012, 05:44:38 PM
I just ordered the 2-ACA board. Can't wait.

Does anybody see any problems with using the +/-24V rails in my console if I use diodes in series on both rails to drop the voltage on the way into the 2520 opamps (down to the +/-16V to  +/-18V operating range?)

Also, Jeff, regarding the Excel chart on pg.7 of the thread, if I type 33K in the RF box (that's what my buss resistors are) and 47pF in the Cf box, I'm getting a Cutoff frequency of about 102K. Does this sound about right? Just making sure I'm using that handy excell chart right.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on February 01, 2012, 12:35:42 PM
Okay, most of the parts are in the mail. Yes!

I'm bumping my last questions though. And asking one more. Does anybody have a recommendation for a really tight tolerance 10K stereo pot? I've decided to just use a pot with a knob since my fader throw length on my console is obscenely long (130mm) and it would require some ugly modifications anyway to use a P&G.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on February 03, 2012, 05:25:34 PM
Jeff,

My above math is incorrect.

Can you tell me if this is correct?

If I'm following correctly, with the equation Gain=Rf:Rs, with Rs at 33K, and Gain at -.6, I'm getting 19.8K for Rf.

If adjust Rf a little to 19.5K, and then use a 68pF cap, I'm getting a cutoff frequency at 120K
Is this correct?

(Edit: Wait, I'm confused as to whether I'm changing R9 and R12 as well? )

Also, concerning my question about dropping the voltage going into the the opamps with diodes in series, I guess I'll just try it and see. How tight does the tolerance need to be between the +/- voltage rails?


Sorry for my question bombardment. I am learning slowly. . . . .
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 03, 2012, 06:27:07 PM
Jeff,

My above math is incorrect.

Can you tell me if this is correct?

If I'm following correctly, with the equation Gain=Rf:Rs, with Rs at 33K, and Gain at -.6, I'm getting 19.8K for Rf.

If adjust Rf a little to 19.5K, and then use a 68pF cap, I'm getting a cutoff frequency at 120K
Is this correct?

(Edit: Wait, I'm confused as to whether I'm changing R9 and R12 as well? )

Also, concerning my question about dropping the voltage going into the the opamps with diodes in series, I guess I'll just try it and see. How tight does the tolerance need to be between the +/- voltage rails?


Sorry for my question bombardment. I am learning slowly. . . . .
I get 19660 ohms for feedback R so I'd use a 19k6 which is a standard value. Yes, 68pF for the feedback caps C11 and C15. You only need to change R10 and R13. Leave R9 and R12 as they are.

I think if your rails are within .75 volts of each other you will be fine. Dropping the voltage is a different subject in itself. I am pretty sure you can find tons of info if you do some searching.

Cheers, Jeff
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on February 05, 2012, 11:11:23 PM
Thanks Jeff.

One more quickie question.

If I understand the schematic correctly, on the 2-ACA-BO, the polarity is being flipped first by the 2623-4 transformer, then flipped back again by the 2503 on the booster side? 

I guess what confused me about this was reading about the implementation (and title) of the 4 Channel Inverting ACA card. I'm not using that card, only the 2-ACA, but it seems that that card flips the polarity as well? Or am I wrong about that? A polarity flip X 3 is obviously going to end up with a reverse polarity in the end.

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 05, 2012, 11:38:19 PM
Thanks Jeff.

One more quickie question.

If I understand the schematic correctly, on the 2-ACA-BO, the polarity is being flipped first by the 2623-4 transformer, then flipped back again by the 2503 on the booster side? 

I guess what confused me about this was reading about the implementation (and title) of the 4 Channel Inverting ACA card. I'm not using that card, only the 2-ACA, but it seems that that card flips the polarity as well? Or am I wrong about that? A polarity flip X 3 is obviously going to end up with a reverse polarity in the end.
Both sections of the card (ACA and Booster) are using the inverting side of the respective opamp. The polarity is being flipped back by each stage's output transformer.

When using the 4 channel inverting board (if combining a large # of inputs) I flip the polarity at the output of the ACA section (post 2623-4), which is essentially leaving it since it was already flipped back to in phase by the ACA's opamp which is the second inverting stage. So, technically 4 flips.

Hope that makes sense! That is some hard stuff to try and type so it makes sense!  :o
Jeff
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on February 12, 2012, 01:35:28 PM
Unbelievable!

Finished installing the ACA in my console yesterday. Easily the best modification I've ever done to anything.
I can't believe it worked perfectly right away, as well. Somehow my grounding scheme worked perfectly on first try.

For right now I'm using my consoles +/-24V rails to power it, and using 4 Hardy 990C's. I haven't even tried the 2520's yet, until I figure a better way to drop the voltage than 1 pair 317/337 regulators.

Anyway, thank you thank you thank you Jeff! I can't believe how alive and defined everything is now. It's really encouraging hearing the emotion/realism of old tracks that I KNEW went down, but somehow was partially lost when summed through the console's previous 2 buss. I realize I actually recorded those tracks pretty well after all!   
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on February 12, 2012, 01:59:54 PM
Awesome news JW! Congrats on your success!

Hey, nothing at all wrong with staying on 24V and running the 990C's. Killer opamps for sure. Who knows, you may go thru all the work to drop the voltage and find out you prefer the higher voltage rails with the 990C's. IIRC, Whistlerock has 918's that will also run on 24V rails.

Best, Jeff
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: TimRandolph on February 15, 2012, 11:17:42 AM
Hello!

I'm new here. Been lurking around for quite a while though.

I'm interested in building some submixers for my unbalanced gear (keys, fx).

Was thinking about using the ACA board for summing, and something like this for the mixer circuit:

(http://i41.tinypic.com/r1wf2t.gif)

( taken from http://www.all-electric.com/schematic/simp_mix.htm )

I would like 16 mono inputs.

I'm getting a fairly good sense of what is required by reading this thread, but I have some questions on the exact values / circuit.

if you take an unbalanced signal from Martin's line boards to a dual 10k linear pot, slugged with a couple of 2.2K R's(season to taste for -dB point when at center), connect each wiper to a 47K bus R, then connected all the bus R's to the inputs of the ACA, keeping Left and Right separate. That is pretty much it.


So the resistors after the pan pot should be 47k...

The pan circuit recommended above specifies a dual 10k linear as opposed to the single 10k in the schematic. I assume the dual-pot circuit lessens the insertion loss? By "slugged" does that mean the the 2.2k resistors go from the "input" of each pan pot to the wiper?

In the schematic shown, there are 10k resistors between the blocking cap and the pan pot... do these remain necessary with the dual-pot pan circuit? If so, what would the proper values be?

I'm guessing that keeping the blocking cap would be a good idea.

And, finally, what would be the proper value for the level pot? Would a linear or audio taper be appropriate?

Forgive all the basic questions. Obviously just learning about all this mixer stuff. Big thanks to Jeff for making these boards available!

Tim
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Jannee on February 15, 2012, 05:35:21 PM
Hi Guys! I thought I'd share with you our exciting project.

I got a MS Audiotron Multimix modular console which was used as a monitor mixer in finnish National Opera during 1992 to 2007. The console has 16 input channel's and 16 aux sends. No channel faders or master bus whatsoever... The Mic Pre's on this are top-notch with Lundahl input trafos and simple eq.
These custom build desks were used in theatres all over scandinavia and europe too. The company went down in late 90's and no one was able or willing to continue to manufacture the se wonderful consoles any longer. You can still find them here for a reasonable price and they are being modified for ob preamps and summing mixers.

The fun thing is that I all so got a huge AMS Neve Logic 2 digital console from Opera's studio too. Now running that thing in a studio these days would be a nightmare and trying to sell that 300 kg of nowadays worthless gear wouldn't make any sense, so I thought we'd tear it apart and use the really solidly build body as a frame for our modular analog MS Multimix console.

Here's some pictures of the parts and pcb's:
www.wolf.fi/multimix

So... I've been thinking of doing the 2 ACA master bus mod for this baby. Other mod will be direct outputs.
We only need 6 auxes so we will have plenty of space in the AMS frame, which luckily happens to take the aux, buss and fader modules just fine, only the input modules need a little metal work.

Allthough I have a technician taking care of the build I would appreciate your input or ideas on the build.

Cheers,

Janne Huotari
Flow Recording Studios
OULU, Finland

(http://www.wolf.fi/multimix/test-fitting.jpg)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on May 21, 2012, 04:15:38 PM
Hello all,
I've been building a stand-alone active summing amplifier based on the JLS-Inv and ACA pcbs from ClassicAPI. I've got a hybrid studio with no console - my goal with this is to be able to sum up to 16 drum tracks through the ACA, to give them some analog vibe, and to allow me to strap a compressor and EQ across the entire drum bus.

Anyone see any issues with this signal path?
DA converter>47K resistor>JLS-Inv(left channel to one side, right channel to to other)>right side of Classic ACA-bo>10k stereo fader>right side of ACA>Left and Right xlr's>monitor controller, AD converter, etc.

I am sending a mult of the final output to a pair of VU meters. Power is coming from a Five Fish PSU kit. I am not connecting the jumper between the two sides of the JLS pcb, so one side cover the L channel, one side covers the R. It all goes in a 2U rack case with DB25 in's and 2 xlr outs.

I was going to unbalance the line in signal by floating the low side. Basically I was going to solder eight positive legs at a time to a turret board post, solder the 47k resistor across to the opposite post, and then send one wire into an input of the JLS pcb. Ditto for the rest of the channels until I have 16 stereo pairs going in.

Anybody see a reason that wouldn't work? Much thanks!
JSmith
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 21, 2012, 07:51:36 PM
If I am following you correctly, it sounds like it should work. Are you buffering the feed to the VU's? You will want to do this with a cheap dual chip of some sort.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on May 22, 2012, 01:45:19 PM
Thanks for taking a look. Yes, I am using a kit from JLM audio to buffer the VU's:
http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=19 (http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=19)

I've found that when you are working semi- in the box, analog summing adds a subtle but noticeable amount of spaciousness and presence. I will probably use this box mostly for drums, and send the drum mix into another summing amp I already have along with other mix elements. It gets me a little closer to having multiple busses in the analog realm like I would if I had a console. Someday...

There are a few good summing amps on the market (Dangerous Music, Tube Tech, Black Lion). I think your ACA circuit would make a great equivalent kit for the DIY world.
JS
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: area8 on June 11, 2012, 08:27:37 PM
I'm positive that some of Jeff's ACA buyers must be building summing boxes to be used with DAWs, etc., as opposed to being part of a larger mixing console.

I'd love to see any pics of your work. They don't have to be pretty, just have to use the ACA board(s). I'm looking for ideas.

I've already built the boards, and keep struggling with how to rack this up - I keep vacillating back & forth between a really simple L & R summing box with few or no controls (simple 2bus, separate L&R inputs) to a (Neve 8816-like) mixer with pan & level controls, etc. I plan to use buffered VU meters on the 2bus, whichever way I go.

Anyway - anybody want to share?

Thanks,
Frank @ Area8
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: wolfgang on June 12, 2012, 05:59:23 AM
Hello!

There is project on the board which uses the ACA-Bo.
Thread is here:
http://www.groupdiy.com/index.php?topic=41430.0 (http://www.groupdiy.com/index.php?topic=41430.0)

If you want to save some money i would build the input stages with IC-LineReciever like the ones from THAT.

If you want Volume, Pan and maybe a Solo/Mute-Function things get more time- and money consuming.
I build a small Mixer with that features based on the ACA but build my own PCB´s. It was a lot of time and not really cheap but i like it alot!!!!
Small thread can be found here:
http://www.groupdiy.com/index.php?topic=48128.0 (http://www.groupdiy.com/index.php?topic=48128.0)

kind regards,
Wolfgang
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: area8 on June 16, 2012, 01:21:30 AM
Wolfgang - thanks for the pointer, and I like your mixer - nice work.  Exactly the sort of thing I was hoping to see.

I've used the THAT 1200 series receivers before with very good results, and the price is right at Mouser, so your recommendation is a good one. I like the 2520 family DOAs as much as anyone and don't mind building them, but seems like a bit of overkill for the application, especially when you follow it with two or three stages of DOAs and iron, anyway. Another tempting input possibility is to take the Black Lion approach, and use a bunch of Edcor 10K/10K transformers for pretty cheap (~$12/ch) and really minimal work.

I already have a decent mixer (Malcolm Toft Trident-like thing), so I'm not ready to embark on something too full-blown, but it is tempting if the sonic results are worth the work. Actually, the ACA would be a much better summing bus for the Toft, but there isn't any room to mount it internally; I'd have to work out an outboard solution. My downfall is really metal work.

I kind of liked the use of simple LCR assignment switches to save money and panel real estate... I think one of the Dangerous boxes do that, don't they? On the other hand, it would be perfectly usable for my application to have dedicated R & L inputs, and do all my panning and levels in the DAW before the outboard summing. I'd likely also use the box to sum a bunch of old Ward Beck preamps I have, as well as some of Jeff's preamps. I sort of have a nasty mic pre fetish, and have far too many for my needs, including a bunch that I've done on perfboard and such over the years.

I'm torn about I/O connectors, though - I'm leaning toward XLRs, instead of going the DB25 route, although I guess I could just run DB25s from a patch panel and still have the same flexibility with the XLRs or TRS. I'll likely just prototype things with a stock XLR panel (like the ones from Middle Atlantic), without any metal work, and mount a power connector in one of the punchouts, instead of mouting a power supply inside.

I like Jeff's new VU meters - they are tempting to use for this, also.

Speaking of VUs, and only slightly off-topic: I'm trying to find which model VUs that Neve uses in their 8816 (I have a blank 8816 panel) - anyone have one you could peek at? I know that they are in a 27mm cutout, and that probably points toward Sifam (along with the fact that they are British and used elsewhere by Neve), but I haven't seen the same model as a stock offering.

Many thanks for the links.

Cheers, Frank
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JayDubrek on June 27, 2012, 11:19:52 AM
Hey Jeff, you still selling these boards...can't find them in your site anymore!
Cheers
Jay
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 27, 2012, 11:29:00 AM
Hey Jeff, you still selling these boards...can't find them in your site anymore!
Cheers
Jay
Yes I am. I ran out last week but have more coming in this Friday. For some reason, the item was "hidden" when the last one was purchased. I just changed that and updated the expected date.

Sorry for the confusion and thanks for pointing it out!  ;)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JayDubrek on June 27, 2012, 11:31:34 AM
Awesome! Still in the early stages of my console build and panicked I'd missed the boat on them!!
Cheers
Jay
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gandhalf3 on August 14, 2012, 06:25:18 AM
Hello, i need some help to accomodate the Rf, and Cf, of my ACA-Bo in a vintage mixing desk ("Saje"). The bus resistors of the mixing desk are 22kohm. the mixer is 30 channels.

I'v dowloaded  the gaincharts.xls by bob Schwenkler. but i dont understand well all of this.

What must be the values of  Rf and Cf on the ACA, to not overdrive its input stage too early ?


regards,

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 14, 2012, 10:55:36 AM
With 22k bus R's, use 13k as the Rf and 100pF as the Cf.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: electrisizer on August 15, 2012, 02:46:33 PM
Hey there,

i have an old 089 studer stereo chanel strip (line in, mic pre EQ) that i want to rack and searching for a line driver modul.

the output of the unit is unbalanced and if ive red the shamtics right @-10db. i want to have balanced output with studio level - so i think about an API solution because i like API :)

ive seen that the api chanel strips have an 325 line driver.

so what do you think about adding this driver to the studer unit?
may there be impedance problems?
and jeff do you still have those 325 PCBs (best in stereo) on sale?

kind regards
nico
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on August 24, 2012, 07:18:24 AM
Hello everybody,

I know this might sound boring but does anyone have a good working solution to get the insert return balanced pre fader?
I find it really important to be on the safe side and don't want to have special patchcords for it.
My setup will often change concerning gear to be inserted.
I read somewhere here that a transformer might be a solution.If so,what specs would you recommend?

Thank you in advance,

Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: wolfgang on August 24, 2012, 07:14:42 PM
What about a line reciever like the THAT 1246 or similar?
I find it a very transparent solution!

regards,
Wolfgang
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on August 24, 2012, 07:31:17 PM
What about a line reciever like the THAT 1246 or similar?
I find it a very transparent solution!

regards,
Wolfgang
Thanks Wolfgang,

but I´d like to keep it all-discrete if possible. ;)
If nothing else works (what I don´t believe) I can still do it like you recommend,have even thought about that as a last possible solution.

Best regards,

Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 24, 2012, 07:39:26 PM
In the modular console project, I am using my DTO5 as a receiver before the fader. Is a very simple circuit not to different from the input channels on the boards you just got.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on August 30, 2012, 09:43:04 AM
Hi Jeff,

2ACA-Bo & Co. received here in germany.Top parts and pcb as always.
Thanks a lot for the L-brackets (EA2503),I totaly forgot to order them!
May I pay them with my next order?
Excellent service here!

Best regards,

Udo. :)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: glazer56 on September 02, 2012, 05:07:24 AM
Hi Jeff,
finally getting around to putting those ACA boards to use that I've bought a few years back!. I am attempting to build a 16 channel summing mixer on steroids, with the provision of adding another 16 channels later. :o I am planning on adding an additional bus or four, and a few sends as well. They say a picture is worth a thousand words, so I'm wondering if the block diagram below would be correct for this configuration? I would need to order a few more boards from you, and want to be sure I know what i'm getting into here! Many thanks for your help, as always!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: glazer56 on September 02, 2012, 05:11:43 AM
Hmm, just noticed that I don't need the two ACA boards for the effects return, as they can feed the master 2 bus directly.... oops!  :o I shouldn't do this at 2am i suppose!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 08, 2012, 04:06:51 PM
Hi folks

I am joining the thread because I just bought this module and I am planning on building a 16 channels summing box.
I am planning on having 16 balanced inputs going to hard left / hard right, this module as the final master section, using its stereo insert if needeed and if possible a pair of nice VU meters.

I am taking any advice, starting with the resistors value... =)

Any help is welcome, and congrats for this cool thread

Thomas

edit:

By sneaking on the forum, I found this http://i52.tinypic.com/21dqvqc.png and I think this is what I am going to aim.
Do you think I can simply grab the stereo out and get into the API module? Do I need to match up the impedance? Or tweak some other value?

Thanks
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on September 08, 2012, 04:47:00 PM
Hello,

the schemo in your link above is just a passive summing network meant to drive a mic preamp.
Don't know if it can be tweaked to work correct with the aca part,at least the shunt resistors should be omitted.Also from what I have seen so far is that the aca is working with 47k bus resistors.

Cheers,

Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 08, 2012, 04:49:57 PM
Thomas

You will need to unbalance the outputs of your proceeding devices. It will be device dependent on whether you float the - side or shunt it to ground. The bus R's for the summing network should be 47k. Also the 237R shunts will not be needed.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 08, 2012, 06:36:07 PM
Thanks for all those informations.
Do you think it is better to unbalance the signal right out of my soundcards, or after the summing and right before hitting the ACA module?

I like the 2nd option better because it gives me the opportunity to pretty easily turn my summing box into a passive one if needed.

When you say that the bus R's must be 47K, does this mean that the whole summing stuff must have a 47k impedance? Because this seems pretty hard if I have to put 10K resistors on each input...

I am a bit lost here...
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 08, 2012, 07:02:00 PM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 09, 2012, 06:27:43 AM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on September 09, 2012, 05:20:15 PM
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
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 10, 2012, 05:46:44 AM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on September 10, 2012, 07:31:25 AM

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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 10, 2012, 02:19:28 PM
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?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 10, 2012, 03:21:44 PM
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?
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on September 10, 2012, 03:29:20 PM
This was not a good example because the 4K has a VCA based master fader, but you see my point anyway :)
aaaah,you meant an ssl 4k.Yes,that's o.k. on vca based consoles,same as on ours,pardon me!

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.
Cool.
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?
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 17, 2012, 09:15:59 AM
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?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 17, 2012, 09:27:24 AM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on September 17, 2012, 09:48:04 AM
Ok, how many amps do you think I need to do this properly?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 17, 2012, 10:04:59 AM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on October 02, 2012, 04:21:07 AM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on October 04, 2012, 11:13:01 AM
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!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Humner on October 07, 2012, 09:38:24 PM
What is the lowest voltage the DOA's can operate? I have a few PSU's I've built off of the 7815 and 7915 chips
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gar381 on October 08, 2012, 02:23:00 PM
What is the lowest voltage the DOA's can operate? I have a few PSU's I've built off of the 7815 and 7915 chips

Hey Hummer

If your using gar2520 or gar1731 DOAs...  a PSU based on 7815/7915 will work fine. (+15v/-15v)

Best..

GARY
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on October 08, 2012, 02:44:14 PM
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?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 08, 2012, 02:46:12 PM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Aniol1349 on October 08, 2012, 03:54:55 PM
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 (http://www.allen-heath.com/uk/Products/pages/DiscontinuedProductDetails.aspx?productId=System8)

Any advice will be much appreciated!

Thanks
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 08, 2012, 04:11:44 PM
Looks doable. I see 12k bus R's on the input channel skiz.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Humner on October 08, 2012, 09:16:01 PM
Looks doable. I see 12k bus R's on the input channel skiz.

Would it just be a matter of changing these to 47k?

Funnily enough I have a allen and heath system 8 as well(MKII though), however mine is in a very sorry state. I've toyed with the idea of stripping out the buss section and making my own 8 channel summing mixer with the 2-aca-bo.

What is the lowest voltage the DOA's can operate? I have a few PSU's I've built off of the 7815 and 7915 chips

Hey Hummer

If your using gar2520 or gar1731 DOAs...  a PSU based on 7815/7915 will work fine. (+15v/-15v)

Best..

GARY

Cheers, I think I'm going with gar2520
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on October 08, 2012, 09:23:08 PM
....Would it just be a matter of changing these to 47k?....
No, do not change what is there. You would just have to adjust the feedback R and C of the ACA stage. There is some talk a few pages into this thread on what to do.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Humner on October 08, 2012, 09:36:24 PM
....Would it just be a matter of changing these to 47k?....
No, do not change what is there. You would just have to adjust the feedback R and C of the ACA stage. There is some talk a few pages into this thread on what to do.

sorry, you are right, I do remember reading about this eariler on in the thread.

Aniol1349, if youh ave the 168 desk, you may have some room above the buss section for the aca boards. I have the 1616 desk and there is no room for anything.

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on October 09, 2012, 03:58:54 AM
Well I have only one PSU here that delivers 16V and a 280hz hum can hardly be PSU related right? The PSU part is located behind a shield that is soldered to the ground... I didn't seem like PSU noise.. More like a leaking cap.
Or maybe a ground loop but if it disappeared it's weird.

Concerning the pot, can someone tell me how to wire it properly? 
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Aniol1349 on October 09, 2012, 04:54:45 AM
Quote
Aniol1349, if youh ave the 168 desk, you may have some room above the buss section for the aca boards. I have the 1616 desk and there is no room for anything.

I do have the 16 16 version, well I'm still waiting for it's arrival so I will have a look into it soon..

meanwhile I'll have a good read of the thread
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Scrappersa on October 20, 2012, 04:05:06 AM
Well I have only one PSU here that delivers 16V and a 280hz hum can hardly be PSU related right? The PSU part is located behind a shield that is soldered to the ground... I didn't seem like PSU noise.. More like a leaking cap.
Or maybe a ground loop but if it disappeared it's weird.

Concerning the pot, can someone tell me how to wire it properly?

Hey Thomas, can you post some pictures or your board or explain in more detail how you wired your summing box? I'm thinking of doing a similar thing. Basically 24 inputs (coming from my soundcard/tape machine), using two inverter boards (6 channels into each op amp), and then going down to the ACA board with the master outputs.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: brennyb on November 24, 2012, 02:40:13 PM
I'm positive that some of Jeff's ACA buyers must be building summing boxes to be used with DAWs, etc., as opposed to being part of a larger mixing console.

I'd love to see any pics of your work. They don't have to be pretty, just have to use the ACA board(s). I'm looking for ideas.

I've already built the boards, and keep struggling with how to rack this up - I keep vacillating back & forth between a really simple L & R summing box with few or no controls (simple 2bus, separate L&R inputs) to a (Neve 8816-like) mixer with pan & level controls, etc. I plan to use buffered VU meters on the 2bus, whichever way I go.

Anyway - anybody want to share?

Thanks,
Frank @ Area8

hey frank i have just finished a build as you mentioned in your post for summing the 8 sub busses of my soundcraft 500 mixer i will be posting pics up later this week after a little snagging and testing. i'm also willing to post up my circuit and block diagrams although a bit rough for some more insparation. Although i can not offer full support for the build i'll do what i can now and then they may be a good starting point.

Just a quick question to all: the soundcraft 500 has a balanced output impedance of 600 ohms i believe. would i need to place termination resistors across pins 2 and 3 (+ & -) on the XLR  inputs to a passive summing network prior to the 2-aca board?

and the same question for the outputs after the 2aca bo implemented in the way of jeff's block diagram for layout?

any help on this would be very much appreciated.

Brendan.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: electrisizer on November 25, 2012, 02:13:17 PM
Quote
Hey Thomas, can you post some pictures or your board or explain in more detail how you wired your summing box? I'm thinking of doing a similar thing. Basically 24 inputs (coming from my soundcard/tape machine), using two inverter boards (6 channels into each op amp), and then going down to the ACA board with the master outputs.

hey there!!!

i have the system 8 too (1616 mkII). i really loved working on this board 10 years years ago especially EQs then it goes into cellar. now im restoring it and upgrades would be great.

first thing is to finish the GDY51 PSU. i have the dual VPR version with one rail +/-15v for the board and the other +/-16v for my GDY51 rack...

im thinking of upgrading the master/summing section too. i dont need the mixers control room, talkback or something else (all done with rme mixer). just EQ, summing and routing the busses will be done on the mixer.

i imagine a ACA summing would be graet  :D

theres really no place inside the board - BUT i dont need the monitoring 16 channels. removing the PCBs is easy. this is enough to fit the ACA thing.

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on December 02, 2012, 05:14:44 PM
Hi all,
A while back I made a stand-alone 16ch summing box basically following the block diagram on Jeff's website for the ACA project. (sound card>47k resistors> JLS-Inv>ACA/Bo>patchbay). Cold side of the signal is floated at the sound card.

Could anyone take a look at this small schematic and proofread it for me? This is my very first attempt at drawing a circuit and having a custom pcb made. Just beginning to learn a little bit about using Eagle...

I wanted to clean up the input to my box a little bit with this tiny board. It just allows me to use a through hole db25 connector and provides pads to solder in the buss resistors. (Less messy wires....) It also allows me to have outputs 7&8 be summed to mono.
I will add channels 9-16 to this circuit by basically duplicating what I have here. My main question is if I handled the mono-ing of channels 7&8 correctly. From what I gathered from this thread, sending the L and R through their own 47k resistors is correct. But what about placing a resistor ahead of these two resistors for a 3db drop? What value would that be?
Any feedback would be really appreciated.
thanks!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on January 08, 2013, 01:58:01 AM
Here's my take on a stand-alone summing amp based on Classic API's ACA circuit...it's an 8, soon to be 16 channel summing amp.

I was having some noise issues with connecting my balanced audio interface into the unbalanced JLS-Inv/ACA circuit. I took a shot at putting together a set of THAT 1200 line receivers on a perfboard, and that made it a lot quieter. Eventually I would like to have a pcb made for that (and lose all the messy wiring...). It's set up for 8 input channels. I would like to do another set of chips for 8 more inputs soon. Channels 7 and 8 are each routed to both channels for mono tracks.

For the fader, I found a balanced stereo 10K Valab 23 step pot (http://www.ebay.co.uk/sch/m.html?_nkw=valab+stereo&_sacat=0&_odkw=&_osacat=0&_ssn=vintage_audio_lab (http://www.ebay.co.uk/sch/m.html?_nkw=valab+stereo&_sacat=0&_odkw=&_osacat=0&_ssn=vintage_audio_lab).
Using another pair of THAT 1200's I was able to send the balanced feed from the 2623-4 transformers through the pot, then out to the 1200's to unbalance before going into the ACA booster stage. That made it quieter still.

Also in the mix are a power supply from Five Fish, VU's from Hairball, VU buffers from JLM Audio, and a handy "ProtoBoard-3U-Conn" from Mouser which comes set up with a set of holes for a DB25 pcb mount connector. I used a 4PDT switch to allow for pre- and post- ACA booster metering. Dan at Collective Cases made the case for me.

Fun.
It sounds sweet. It definitely adds a little spaciousness and weight to the drum tracks I've run through it so far.

(http://)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: EHPro on January 20, 2013, 04:05:58 PM
So I bought a used aca 2 bo racked in a case as a summing bus in varying degrees of condition and after having it for several months am finally getting around to fixing and Rewiring it. I've always loved the API sound and am excited about getting it finished.
I went with 20k bus resistors and with Jeff's help recalculated the FB resistor and caps. I'm self informed from the internets diyer so excuse my ignorance. R3,8,11,14 were not stuffed on the board. Are these needed and what do they do? I was trying to source a good dual deck non stepped pot in the US under $25 and there seem to be a lot of options. I have an alps rk27 dual 50k on hand, could this work if I change r1 and r5 or will my fader throw give less than desirable results. On grounding I decided to use some spade lugs to a central point so I can disconnect one by one for testing. So dsub gnd to star, summing network to aca bus gnd to star and aca 2 bo to star. Where would be the best mounting point of aca 2 bo to use for this or should I gnd all of its mounting points and use one to connect to the other grounds. Seems to defeat the term star ground at that point. Thanks for any help on this old thread.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bubble on February 12, 2013, 08:43:09 AM
Hello,

can i use the 2-ACA in replacement of the summing amp, post fader amp and balanced output amp in the master section of a soundcraft delta 200. The board is powered +/-17V.
Will i keep the monitor section fully functional ? (Regarding to the schem i guess yes, but i'd like to be sure).
What do you think of this mod ? Is t stupid to use 2 really differents electronic designs in a same board ?
This board is usable but in my sense the master section is not good enought to be use to sum my mixes thru. In the other hand i use api-sh style pre's for recording, i really love them, musician friends too (i exclusively record 90's indie rock/shoegaze). would it be an improvement in my api-sh sounding quest ?

Thanks,
Guillaume
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: electrisizer on February 12, 2013, 09:06:10 AM
Hello,

can i use the 2-ACA in replacement of the summing amp, post fader amp and balanced output amp in the master section of a soundcraft delta 200. The board is powered +/-17V.
Will i keep the monitor section fully functional ? (Regarding to the schem i guess yes, but i'd like to be sure).
What do you think of this mod ? Is t stupid to use 2 really differents electronic designs in a same board ?
This board is usable but in my sense the master section is not good enought to be use to sum my mixes thru. In the other hand i use api-sh style pre's for recording, i really love them, musician friends too (i exclusively record 90's indie rock/shoegaze). would it be an improvement in my api-sh sounding quest ?

Thanks,
Guillaume

some posts above ive had the same idea, but havent done it... i dont want to risk my boards health ;) so im going out of my master insert out into a high quality preamp or whatever im patching in there (at the moment its a stereo 1084 neve clone EQ from bluzzis project, im loving very much). i think its the safe way and i like what i hear in comparison to the boards master amp (tl72 i suppose).
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bubble on February 12, 2013, 09:26:51 AM
Its an idea. I do this kind of thing with a passive mixer. But the idea here is to replace the summing amp to improve summing in the desk. The summing amp is before the master insert point.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bubble on February 12, 2013, 09:31:08 AM
And regarding the schematic, in this way u doesn't have the cr section usable cuz you disconnect the output amp that feed the control room section. Right ?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: electrisizer on February 12, 2013, 10:53:57 AM
And regarding the schematic, in this way u doesn't have the cr section usable cuz you disconnect the output amp that feed the control room section. Right ?

yes but perhaps you could feed a master stem of your DAW via the DA converter to the return of the insert. e.g. the RME totalmix can do this without latency if you are on rme system... for sure summing is not improved :(

if the soundcraft has direct outs for each channel you can sum with passive circuit and make up gain amp.

because after hearing some opinions about a system in a system like aca summing in a existing board i found it too dangerous. but perhaps im wrong and its a good improvement... if you try let us know the result! itxs exiting for sure :)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: bubble on February 12, 2013, 06:59:40 PM
Quote
yes but perhaps you could feed a master stem of your DAW via the DA converter to the return of the insert. e.g. the RME totalmix can do this without latency if you are on rme system... for sure summing is not improved

I can do that with my motu system but as you say summing is not improved.

Quote
if the soundcraft has direct outs for each channel you can sum with passive circuit and make up gain amp.
no direct out and in this case, no pan and bus assigns.

Just want to improve the summing quality of the desk to make it usable in a mixing setup. There's a lot of mods for the old soundcraft line, but the aca seems to be a really good way to change the desk in something at my taste. Just d'like to know if it's suitable and if it's a real improvement.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on February 21, 2013, 01:29:18 PM
I'm in a similar boat to JW back on page 11 with a Yamaha PM2000.  Those familiar with the console know the strange signal flow: input channels assignable to->  8 mono programs which can be mixed individually to-> 8 matrix summing amplifiers/outputs.  All programs and matrixes are currently mono.

My wish would be to replace one pair of matrixes (matricies?) with the 2-ACA-Bo as well as 1 pair of programs.  Ultimately I'd like to be able to keep the programs assignable for subgroup duties.  I understand the JW replaced a pair of the program summing amps with the ACA and it worked well.  The downside is that to use this as his 2buss he now has no subgroups.

I don't understand how much gain is being added in each stage that I'd like to replace.  My other concern is that I will have to loose a bunch of switching/functionality to shoehorn these things into an existing circuit. 

If anyone wouldn't mind, it'd be great to have a second, third fourth set of eyes on the schematic/block diagram.  The output buss resistor is 33k which in not on the attached schematics.  It is a 32 channel desk BTW.

Should I be looking at the Inv-ACA for the program (subgroup) duties (to keep gain at unity) and the 2-ACA-Bo for the 2 buss?

Sorry for so many questions... :P

Many thanks in advance!

Josh
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: grubbyliver on February 22, 2013, 01:41:11 PM
Quote
I'm in a similar boat to JW back on page 11 with a Yamaha PM2000.  Those familiar with the console know the strange signal flow: input channels assignable to->  8 mono programs which can be mixed individually to-> 8 matrix summing amplifiers/outputs.  All programs and matrixes are currently mono.

My wish would be to replace one pair of matrixes (matricies?) with the 2-ACA-Bo as well as 1 pair of programs.  Ultimately I'd like to be able to keep the programs assignable for subgroup duties.  I understand the JW replaced a pair of the program summing amps with the ACA and it worked well.  The downside is that to use this as his 2buss he now has no subgroups.

I don't understand how much gain is being added in each stage that I'd like to replace.  My other concern is that I will have to loose a bunch of switching/functionality to shoehorn these things into an existing circuit.

If anyone wouldn't mind, it'd be great to have a second, third fourth set of eyes on the schematic/block diagram.  The output buss resistor is 33k which in not on the attached schematics.  It is a 32 channel desk BTW.

Should I be looking at the Inv-ACA for the program (subgroup) duties (to keep gain at unity) and the 2-ACA-Bo for the 2 buss?
I hear you as I'm also in a similar boat, looking to add 2 bus functionality to an old Allen and Heath mod3 console (16x8, modular, discrete), I'm still weighing up the pros and cons. inv acas would be great as a solution for the busses except that as they are not intended for this purpose there would be no fader or sends on the groups. It might be possible to modify the boards to do this but it starts to get messy with wires all over the place, grounding etc

Right now I'm considering starting with adding Jeff's aca +bo board and working backwards from there - building a new monitor section and perhaps stealing a pair of busses from the aux, (or from power distribution and wire them separately instead) to use as stereo bus feeds. Ideally - 1 aca bo board per pair of groups on our desks!  then sum them through resistors into the master aca. Still working it out but I would like to keep the 8 groups and just add the 2 bus if possible.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on February 23, 2013, 04:07:58 PM
Quote
inv acas would be great as a solution for the busses except that as they are not intended for this purpose there would be no fader or sends on the groups. It might be possible to modify the boards to do this but it starts to get messy with wires all over the place, grounding etc

Right now I'm considering starting with adding Jeff's aca +bo board and working backwards from there - building a new monitor section and perhaps stealing a pair of busses from the aux, (or from power distribution and wire them separately instead) to use as stereo bus feeds. Ideally - 1 aca bo board per pair of groups on our desks!  then sum them through resistors into the master aca. Still working it out but I would like to keep the 8 groups and just add the 2 bus if possible.

Yeah that's what I can't figure out - how do I utilize the group faders with an inv-ACA and then go to the ACA-bo for stereo buss summing.  Or do I need the ACA-bo's for the groups too?  Seems like it'd be way too much gain that way around.  Perhaps they can be run at unity some how?  This stuff is over my head...


That's my plan as well - backwards from the stereo buss.  I'm going to replace two of the matrix busses (7 & 8) with a 2-ACA-bo and send all of the programs to it.  The programs have a "on-off" switch right before they hit the matrix buss so I should be able to pick them off there - right where it says "to matrix post" in the attached schematic above if anyone cares to check it out.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: grubbyliver on February 26, 2013, 12:53:57 PM
Josh,
I don't see any schematic link but what you're describing basically sounds right, if you give up a pair of busses which will become your new 2 bus feeds then when you select bus 7/8 on the channel modules they feed the aca + bo directly.

Now it seems to me that it should be possible to send busses 1 - 6 into the 2 bus also by somehow taking an unbalanced feed from these busses somewhere and running these through some resistors and into the aca inputs also - may require running some wires between modules but should be doable, leaving you with a 32x6x2 desk. Surely overall summing would be improved by using aca+bo boards on the groups as well but that would be a much larger and more expensive task, indeed there may not be room enough inside your desk to do it.

On the old API desks, i think the 2 bus feed from the groups is taken after fader and booster amp but before the output transformer which may provide a less hot signal but I am not certain of this.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on February 26, 2013, 11:33:26 PM
Josh,
I don't see any schematic link but what you're describing basically sounds right, if you give up a pair of busses which will become your new 2 bus feeds then when you select bus 7/8 on the channel modules they feed the aca + bo directly.

Now it seems to me that it should be possible to send busses 1 - 6 into the 2 bus also by somehow taking an unbalanced feed from these busses somewhere and running these through some resistors and into the aca inputs also - may require running some wires between modules but should be doable, leaving you with a 32x6x2 desk. Surely overall summing would be improved by using aca+bo boards on the groups as well but that would be a much larger and more expensive task, indeed there may not be room enough inside your desk to do it.

On the old API desks, i think the 2 bus feed from the groups is taken after fader and booster amp but before the output transformer which may provide a less hot signal but I am not certain of this.

I must be asleep at the wheel as usual...  Hopefully I manage to get it attached this time.

Looking at the docs on ClassicAPI the topology doesn't look that different between the API and our PM2K.  I just can't decide whether to give up the sub-masters 7&8 as you mention above or to keep all 8 submasters (called programs on the schematic) and replace one of the "matrix" pairs with the 2-ACA.

Basically as I see it (from a routing perspective) if I go the way you say, I give up a pair of subgroups and have to do more wiring to get the subgroups (1-6) to feed into the new stereo bus (7 and 8) - but I gain the ability to send the individual channels directly to the stereo bus.  If I instead replace a matrix pair I keep all 8 submasters but have to route each channel through at least 1 of them to get to the stereo bus...

Decisions... 
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ramshackles on March 05, 2013, 07:24:58 PM
Thinking about building this as a simple summing box for DAW output.

I thought about putting on/off switches after the mix resistors so that I could also treat it as an input selector for my monitors if need be.

However having, say, 16 switches for each pair of channels seems a very clumsy and time consuming switching method (consider needing to switch between a mix on channels 1-15 and some other source on channel 16 :S)

Is there a better way to do it??

Thanks..
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on March 05, 2013, 08:00:12 PM
What about one switch and a bunch of relays?  Too expensive?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ramshackles on March 06, 2013, 03:48:31 AM
What about one switch and a bunch of relays?  Too expensive?

How would it work with just 1 switch?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on March 06, 2013, 03:40:14 PM

How would it work with just 1 switch?

Thinking a little bit more about it - it sounds like you just needed to switch between 2 sources in your previous post: 1-15 and 16 (alternate source).  Is that the idea?  If so (and here's where this goes beyond my knowledge) couldn't you switch the inputs between these two sources?  For example a L/R buss rail for 1-15 and a L/R buss rail for 16 (Aux input).  I'm not sure if the relays being on the inputs of the ACA would cause noise since they are before the summing amp - someone else will have to address that one...

Best of luck,

Josh
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ramshackles on March 07, 2013, 01:32:40 PM
I think I will just have another couple of inputs that avoid the summing card altogether & just use a rotary switch between them to select after the summing...

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on March 25, 2013, 12:45:36 PM
Hey Josh,

I think you should try to wire up the ACA in substitution of a pair of programs first so you can directly compare the difference between the original programs on the PM2K and the ACA. I don't particularly feel it's worth it to be running an entire mix through (a pair of the programs?) on the way to the ACA just so you can utilize two more mono busses. If I understand you right? (actually I'm thinking I'm not understanding you right because this would essentially be the same thing functionally, as you lose the independence of those 2 busses by forcing them to be assigned as the mains on the way to the ACA? Hmmmmm.



The way I plan to do it, I think, is to get (3 more?) ACA boards to substitute for the 6 remaining (mono) programs in the PM2K, and make those routable into the 2 buss ACA. You would have to hard wire these outputs on the back of the buss bar (straight into the main ACA-2), because I don't think there is a way to route a program to a program on the PM2K, without using the matrix (right?)

Anyway, you could run the remaining ACA's on the mixers +/-24V and use the existing yamaha opamps, which sound good anyway, and would save some cash, and you wouldn't need another power supply. Actually, you could do that for the main buss as well, but I sure do love those 2520's.  I'd like to know if the PM2K transformers could substitute too, at least at one stage.

I'd like to hear what Jeff thinks about this. Perhaps he will recommend using the inversion PCB instead for the other busses. But I'd like to retain the direct outputs (at full level) of the other program busses in the PM2k for stuff like bouncing (I'm on 8 track most of the time) Anyway, I'm just thinking out loud here. Probably all things you've already considered.

I think once you hear the difference between the PM2K Programs and the ACA, you'll want to be routing the input channels directly to the ACA, even if it means sacrificing two busses.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JdJ on March 25, 2013, 02:38:39 PM
Hey JW-

Yeah - after much cosideration and talking to Fletcher's tech we are going to use Programs 7&8.  The plan is to make it modular - combining 2 used master section frames, a P&G stereo fader as well as a regulator board for the power and some metalwork so the section can be plugged in to the old 7&8 Program spots.  Obviously we will have to route the connectors to the proper outputs & jacks in the body of the console still so it won't be true plug&play... 

I hadn't thought of using the existing DOAs but that is an interesting idea for when we do the other programs.  We already have some red dot 2520s for the first round.  Have you tried the Yamahas in your ACA?

I figure if we really are jonesing for the existing programs for submixing we can patch them in at the patchbay - we'll have to feed them back into channel inputs but it'll give us the option for a work around if necessary.

Thanks for the input!  PM2K's unite!!!

-Josh
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Fuccimain on May 20, 2013, 05:09:30 PM
sorry if I missed this, but what is the ideal buss source impedance that feeds this ACA-Bo card?  I see on the classicapi  page it says signals should be routed thru 47k buss resistors, and the block diagram shows 2 INV-ACA cards feeding the ACA_Bo card.. so with 8 channels out of the INV on 47k buss resistors,. is the ideal Buss source impedance 5.8k?  thinking my buss source impedance will be around 2.35k, so I'm curious if/what I need to change to make the inputs on the ACA-Bo "happy" .is it feedback resistors that need to be modified?

does that make sense? sorry for nebbish question

s
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on May 20, 2013, 06:54:32 PM
A standard 2-ACA-Bo will easily sum 40 channels or so, all thru 47k bus R's.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Fuccimain on May 20, 2013, 07:27:04 PM
cool.

but is there an ideal load it wants on the input?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: globule_655 on June 11, 2013, 03:40:00 AM
Hi there !
Great thread ! Lots of really useful informations.

I still have a few questions though. I'm planning on building 2 things around the 2-ACA-Bo cards.

First, a summing box using the attached circuit for inputs (sorry for my poor drawing skills...). So my first question is : as this circuit uses the inverting input of the opamp too, I guess I wouldn't have to revert polarity at the output of the 2-ACA-Bo, am I right ? Stupid question I know but I just want to be sure I didn't misunderstood anything.

Next question is about my second build. I want to build a sidecar with mic pres (like 12 or 16 API312 pres), EQ based on the 553 schemo on Jeff's website but with 2 or 3 frequency per band (if at all possible, I'll ask when I build it), direct outs per channel driven by 325 cards with a fader, and 8 busses.

So, regarding buss assignement, can I just add a switch per busses on each channel, each one attached to a 47k summing R or does it require additionnal buffering ? Also where am I supposed to wire this ? Right after the fader and before the 325 card of after if and before output trafo ? Or maybe use a mult after the output trafo ?

Thank you very much !
Cheers !
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Chad.saxton on August 04, 2013, 07:42:41 PM
I am building the 2-aca-Bo and I would like to incorporate a pan circuit.  Does this forum have an opinion on whether I use the dual gang pot method or the single gang pot method?

Thanks


Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Coldsnow on August 14, 2013, 08:03:59 PM
I'm using the booster side as makeup for a pultec filter.  With the 10k pot in front, anyone know what the input impedence of the booster side would be?  Would it be better to use a tpad after the transformer output? 
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Cosmonaut on August 16, 2013, 06:27:53 AM
 I'm working in a little sidecar with 8 modules from a Trident 65, and I'm planning on using the ACA board for the main L-R, but I have some doubts...the main one is what is needed for the the summing amp with main insert and master fader? It's ACA board, 4 DOA and 4 TX?

 The second one is about the summing bus resistor, as I see in the schematics, the R from all busses is 12K(groups, main and auxes), but before this in the main, there is a pan circuit with a pot and a resistor in paralel with the wiper, should I take in account this pan circuit for the maths?

the schematic is on google drive, page 63 is the input circuit diagram.

https://docs.google.com/file/d/0B0LxNUBYfNL8OUFrNnYtQVcxaDg/edit
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 16, 2013, 10:21:34 AM
I'm working in a little sidecar with 8 modules from a Trident 65, and I'm planning on using the ACA board for the main L-R, but I have some doubts...the main one is what is needed for the the summing amp with main insert and master fader? It's ACA board, 4 DOA and 4 TX?

 The second one is about the summing bus resistor, as I see in the schematics, the R from all busses is 12K(groups, main and auxes), but before this in the main, there is a pan circuit with a pot and a resistor in paralel with the wiper, should I take in account this pan circuit for the maths?

the schematic is on google drive, page 63 is the input circuit diagram.

https://docs.google.com/file/d/0B0LxNUBYfNL8OUFrNnYtQVcxaDg/edit
The 2-ACA-Bo will be what you need. You will have to adjust the feedback R and C of the ACA stage to work properly with your 12k bus R's but that will be no problem.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Gachet on September 09, 2013, 09:58:00 AM
Hi there

I have a few questions after reading almost all the post here.
What is the purpose of the two 2623 transformers? Looks like providing balanced output for insert and return is unbalanced.
Do I need those if just want an output fader with no insert point?

Can i use the input 2520 as a differential input amplifier(like in the 2520 brochure? I already have hot and cold separately summed in my config. 

Thanks

PS: jsteiger do you know when EA2503 will be back on stock?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 09, 2013, 10:35:31 AM
Hi there

I have a few questions after reading almost all the post here.
What is the purpose of the two 2623 transformers? Looks like providing balanced output for insert and return is unbalanced.
Do I need those if just want an output fader with no insert point?
Besides balancing the ACA output, they also provide 6dB of gain and bring some "API tone". They can be skipped but you will have to adjust to make up the 6dB.

Quote
Can i use the input 2520 as a differential input amplifier(like in the 2520 brochure? I already have hot and cold separately summed in my config.
The PCB is not designed for this. It may be possible but you will have to check it out on your own.

Quote
PS: jsteiger do you know when EA2503 will be back on stock?
Should be today or tomorrow, from what I've been told.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Gachet on September 09, 2013, 11:28:47 AM
The PCB is not designed for this. It may be possible but you will have to check it out on your own.

Of course, I was asking about the topology. transformer or differential input.
I could also use the transformer before the aca input.

Anyway thanks for the quick answer.
Can't wait to place my order....
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on September 17, 2013, 06:43:43 PM
Jeff,

Are the 2503 transformers wired as 600 ohm output? Just curious. I'll need to go back and do another test, but I was feeding an LA 2A with one side of the ACA the other day and it seemed like maybe it wasn't playing nice, but I may be wrong. . . .
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on September 17, 2013, 07:55:09 PM
No, 1:2 so more like 300 ohms. Should be fine driving a 600 ohm device.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: thomasdf on October 22, 2013, 10:31:48 AM
I am in the process of building a second version of my summing box. The summing is passive thru 47K bus resistors and then the stereo mix goes into the ACA, a Alps Blue 10K stereo pot acting as a master fader, and in the booster section.
Only the right side is working properly...

I am 100% sure about the overall wiring (summing to the ACA, ACA to the master fader, master fader to the Booster section, Booster section to the output) as I doubled checked it and everything is fine.

I have swapped the 2520 around, the capacitors between L and R on the ACA module... Resistors look and test OK...

So I am confused here, because that d*** left side of the ACA is not working...

I know that you guys may not be of a big help without actually seeing the unit in front of you but who knows, maybe I have forgotten something...
Still have a 60hz mains hum but that is not my main concern for the moment :)

EDIT : It is now working. For some reason I had to add 2 straps near the output transformer but it is fine now.
Still need to get rid of that mains hum!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: mitsos on October 25, 2013, 08:25:22 PM
Hi guys, I am getting my hands on an old TAC scorpion and have an ACA-BO (the mixer + booster pcb) that I want to "splice" into one of the groups, so that I can use the ACA for mixing and use the stock TAC module for fader/insert/mute/etc.  I think I figured out the patch points ok according to the schematic and will use shielded cable for this, but I noticed the channels have 10K summing resistors.  I assume I should change the feedback R for unity, would this be 10K?  I know I'd have to change the cap as well...

thanks!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: mitsos on October 26, 2013, 09:07:24 AM
hmm, from what I gather, API used 47K bus resistors, so with 28K that gives a gain of 0.59.  To get this with 10K bus resistors I'd need 5.9K feedback R and 220pF cap to keep the -3dB point at 122KHz... guess I'll try this out and see what happens.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Jannee on November 11, 2013, 02:43:28 PM
My mixer runs from 15 volts power rails, do you think it would be ok for gar2520 op amps in the ACA?

Janne
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on November 11, 2013, 03:00:51 PM
Yes that will be fine.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on January 22, 2014, 12:56:09 PM
Anybody got a recommendation for a high quality stereo potentiometer for the ACA? I was using I believe an Alpha pot for awhile, and it's starting to get scratchy. I don't really need a fader, just a nice high quality pot.

And, Jeff I wonder if you might suggest a tweak? I really like the sound of the board, when said pot is opened up pretty wide. The problem is, when I push the inputs on my board, which I also like to do a bit, it starts to clip my converters. Do you have a suggestion as to where to remedy this, so as not to change the sound of the ACA much, but so I can have it opened up pretty wide, and not be clipping my converters?

Maybe a little more resistance somewhere? Perhaps just a different volume pot,? which is why I started this thread.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on January 22, 2014, 02:46:58 PM
Well, I think any changes to the circuit will alter the way is sounds to some degree. It may take some experimentation to see what alters it the least or in a way you can handle. You could use a balanced u-pad after the final outputs. You could also increase the input series R's in the booster stage. The ones following the insert point and fader.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on February 19, 2014, 01:27:53 PM
Just replying concerning my issue a couple posts ago. Sort of an oh-duh moment. I got a new stereo pot for the ACA, one of these: http://www.partsconnexion.com/product7384.html

It solved my gain staging problem. I get the same wide full range sound no matter where the level is set with this pot. I think I had a crappy carbon stereo alpha pot from the parts drawer in there prior.

So, my advice is, don't skimp on your mixers main output pot/fader! I makes a huge difference.

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Olegarich on March 01, 2014, 05:04:13 PM
I bought console where is installed Aca2 summing system. Inventors and booster. Today I've been reparing channels and something happened to summing ( I might damaged it with channel drop or something else). Left channel doesn't work. I need schematics and other documents if there is any. ON web page there is writen that documents are sended to mail with purchase but I've purchased it from other guy (with console) and it's hard to find him now. Could you please send documents to [email protected]
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Olegarich on March 06, 2014, 02:41:28 AM
hey guys. how you guys resolved afl or solo button thing? i mean now when aca installed afl button doesnt work in my case. in my console afl doing 2 things. first it lets sound to pass in threw it routing and secondly it turns on relay on master section that plugs from mix source to afl source. any ideas?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 06, 2014, 11:40:42 AM
You could probably adapt the talkback function of the 2-ACA-Bo card to your solo bus signal. I assume your AFL sends those channels to a separate solo bus or pair of buses? You will need to see about the logic for that. There will be a logic bus for AFL. You will have to see the state of that bus when solo is off and when it is activated.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Olegarich on March 07, 2014, 06:35:33 PM
yeah it sends afl to separate bus. when it off there is no signal coming in to that bus and when its on then signal goes threw that bus and also same switch turn on relay on master section. so how connection should look like?

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 07, 2014, 08:30:43 PM
Well, actually this should probably be done after the 2-ACA-Bo card. This type of switching would be in the control room module part of the board. The 2-mix signal would typically not be interrupted.

Are you using a monitor controller of some sort, after the 2-ACA-Bo?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on March 08, 2014, 03:17:50 PM
A simple question:
What is the purpose of the 47K bus resistors? Are they involved in setting the input impedance, or something else?
I am summing eight channels through my ACA. Is 47K the value I should be using there for such a small channel count?
thanks!
JS
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Olegarich on March 08, 2014, 04:02:34 PM
hi
 no im not using any monitor controller it goes straight back to the convertor.
by the way how you find which input resistor (47k mostly)
is best choise for your console? i mean how this procedure looks like?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 08, 2014, 04:31:18 PM
47k is just what API used in the vintage consoles. I think that was so subgroups could be assigned or switched off with very little load change to the channel booster amp.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gbesouchet on March 19, 2014, 04:43:00 PM
Hi there,

First post on this thread (though I think I read it all):

I'm planning on building a 24 channel summing, 2 inverter boards, 1 ACA-Bo, so, 12x2520s.
Is it possible to use Classic API floor power supply for it? Is it too overpowering?

Cheers!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 19, 2014, 07:37:33 PM
Roughly speaking, twelve 2520's would be in the neighborhood of 300mA per rail. A Dual VPR PSU will deliver 3A per rail so way overkill IMHO. I have a small 2 rail PSU that is good up to 1A. I need to get them listed at the store.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: gbesouchet on March 23, 2014, 01:38:29 PM
Thanks, Jeff!

Please list it!
I'm thinking about making it 8 stereo ins and 8 mono ins. For the mono's I just need to split the input to 2 different 47k resistors, one to each 4-Inv ACA, is that right?

Regards,

Gabriel
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 23, 2014, 01:55:43 PM
Yes that is correct.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: living sounds on March 30, 2014, 08:17:47 AM
EDIT:

Everything works now and sounds great! Turns out the faders were to blame, also fixed the feedback R and C as described here.  8)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on May 06, 2014, 09:24:00 PM
Hey Jeff,

Just hypothetically speaking . . .

Let's say I have 8 channels of Yamaha PM1000 input strips that I want to turn into a simple mixer on the cheap. Now, let's say I have 4 600:600 output transformers, and also a bunch of Yammie discrete opamps (These opamps are from the Pm2000 and run on +/-24V) However, my power supply for the input strips is +48VDC. It's huge though, a 3A supply. So there's a ton of current available.

I've already built the ACA buss for my big mixer, and I love it. I'm just wondering if there's a way I can make it work for a little portable discrete 8X2 with a not so standard B+ and some different transformers.

Hmmmm.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: GVK on June 20, 2014, 09:18:18 AM
hi.

Could I use the 2 ACA Bo to add some analog color to the stereo bus of my ITB mixes?
I'd be feeding it from the balanced output of my DAW's two channel USB interface.

How much color could I actually add to a mix this way? 
I guess I'd have to hit the transformers fairly hard to make a difference... a result that's not perceivable would be pointless.

Could the circuit then directly drive a pair of active speakers & headphone amp, and be suitable to patch back to the interface so I can capture mixes back into the DAW for file export?

Cheers - S
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Dr_J on June 28, 2014, 01:28:09 PM
Hi Jeff,

I just thinking about the next projects going for  :D
I came up with the idea of a little rack mixer, 4 to 2 or two times 2 to 1.
(Pre mixing some mic preamp signals before going into the DAW).

Then i stumbled over your "Classic Inv-ACA", could he do the job?
Is there a way to add some (mixing) pot faders as well?


ROCK-ON!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JayDubrek on June 29, 2014, 02:30:49 PM
Dr-J... Hakanai is releasing a 4 input version of his 'stereotype' board in the White Market. This will drive four faders and is designed to sit in front of the ACA....  Hope this helps!
Jay
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on June 29, 2014, 02:33:58 PM
An ACA-BO might be even better because you can have a master fader (or pot) then.

Best,

Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Dr_J on July 01, 2014, 02:41:04 PM
Hi,

thanks for pointing me to the Hakanai boards; looks good.

ROCK-ON!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: darnell on August 10, 2014, 03:29:16 PM
Hey all,

Just putting the finishing touches on populating my pcbs.  Wanted to ask a couple questions.  I've already bugged Jeff (who is always extremely helpful) but maybe someone has done this already.

I am looking to build a 16 ch summing mixer with the 2aca-bo on the end, and 4 of the 4ch aca inverting boards.  The idea is to have a 2520 on each input that sums to the 2aca board.  I was thinking just populate 4 4ch boards so I end up with 8 left and 8 right.  I think this would essentially be what is going on with the API 7800/8200 without all the panning/level/mutes, which i don't need.  Is that correct?

With that in mind, would I need the 47k input resistors if I'm only sending 1 signal per 2520 on the 4ch boards?  Or can I just go straight out of my Lynx to a TRS jack with the - floating (or grounded)  to the input of the 4ch aca? Jeff said balancing the inputs might be unnecessary if I'm not doing long runs, and my PB for my Lynx will be a few inches above this summing mixer.   

Also, should I just input my 4ch ACA boards (ch1-4)output into the other 4ch ACA board (ch5-8) via the aux in area to get 8ch per side? it seems like that would tie all the 47k summing resistors to 1 buss point to send to the input of the 2aca-bo. 

Anyone who did this, please feel free to chime in.  I have 2 of the 4ch boards populated and my 2ch aca-bo is ready too, so im going to try to get things going in the next couple days. 

Thanks in advance.

Daryl
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 10, 2014, 03:44:17 PM
Yes you still need the bus R's. They can't be eliminated.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: darnell on August 10, 2014, 06:05:43 PM
Yes you still need the bus R's. They can't be eliminated.

Thanks Jeff!!!

I was trying to avoid bugging you again with more questions. Thanks for once again helping out.

Ill be ordering more 4 ch boards in a couple days.

Daryl
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: skidmorebay on August 25, 2014, 12:56:01 PM
Hi,
I configured an ACA board with THAT line receivers as an eight-in/two-out summing amp, using four gar2520's. It's worked fine for a while. I just acquired four API 2520's date-marked 2010. Strangely, I get frequent intermittent left or right channel drop outs and occasional pops with the API's. I've checked the power supply rails, and both are at +/- 16V.
I re-installed the gar2520's one at a time, but the problem didn't go away until all of the API's had been removed. Hard to believe that all four API's would be defective. Is there any reason that gar2520's would work fine in this circuit but API 2520's wouldn't?
thanks!
JS
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on August 25, 2014, 01:15:44 PM
Not to my knowledge. They should be interchangeable. I would go thru the real 2520's one at a time and see if some or all are bad. Maybe someone sold you some faulty ones?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: AUDIO-ON on September 02, 2014, 05:12:37 AM
Hi there!
I want to build a basic Mixer with the Hakanai Input Boards, 16 channels, and the 2 aca Bo as Summer. My question is about implementing a Monitor controller and headphone amp. The booster has 3 outputs. 1 output as master output. The other output could feed the monitor controller. Is it suitable to feed an passive attenuator without compromising the main output? I think the outputs are transformer isolated? Where can I feed the headphone amp and a VU meter? The -6db output? Or shall I feed the monitor fader from the mult output from the aca board and feed another booster for the monitors?
Thanks,
Rafael
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: living sounds on November 05, 2014, 08:10:04 AM
I love my 2-ACA with APP992 op amps on the mix bus.  :)

But I've got a question regarding the circuit: What's the role of the parallel resistor and cap before the transformers? A cap by itself would be obvious - blocking DC - but the low value resistor kind of defeats that purpose, doesn't it?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on November 07, 2014, 06:57:53 PM
I love my 2-ACA with APP992 op amps on the mix bus.  :)

But I've got a question regarding the circuit: What's the role of the parallel resistor and cap before the transformers? A cap by itself would be obvious - blocking DC - but the low value resistor kind of defeats that purpose, doesn't it?
I would be interested too,maybe Jeff can shine a light on it?
Meanwhile a little question on the APP992: Do you run it from +/-16vdc or the higher +/-24vdc?
I'd like to do some experiments with them too since I made some very good experiences in my other builds.
Wondering if the ACA/BO is safe to use with higher supply voltages.


Thanks in advance,


Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on November 07, 2014, 09:59:03 PM
But I've got a question regarding the circuit: What's the role of the parallel resistor and cap before the transformers? A cap by itself would be obvious - blocking DC - but the low value resistor kind of defeats that purpose, doesn't it?
Well, keep in mind that the 2-ACA-Bo is a replication of what API did in my console. From what I have gathered, the R in parallel with the output coupling cap forms an RC filter to help flatten out the bottom end. Also from what I have found, this was first added to the 550 EQ by Wally Heider in the early '70's. Wally hacked in a 47R in parallel with the 400uF coupling cap before the 2503. This RC then started showing up in the output stage of many other API circuits. Typically, there is very little DC offset especially in the ACA or booster circuits. The actual DC voltage at the opamp's output will drop over the parallel R (easy to measure). It is typically less than 80mV so will be even less when it reaches the output transformer's primary (Ohms law). If there is a major problem and you have a spike in DC offset, the 47R will usually smoke due to the uber high current across it so the output trafo will still be protected. Many of the 512C's and EQ's have charred evidence of this burnt 47R.  :)

If you are using something other than an API style 2520 or 1731, I would suggest measuring the DCV after the RC to make sure you don't have anything higher than 80-100mV.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on November 08, 2014, 02:49:53 AM
Aha,great,thanks for the explanation Jeff!


Best regards,


Udo.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: ppa on November 20, 2014, 08:07:52 PM
But I've got a question regarding the circuit: What's the role of the parallel resistor and cap before the transformers? A cap by itself would be obvious - blocking DC - but the low value resistor kind of defeats that purpose, doesn't it?
Well, keep in mind that the 2-ACA-Bo is a replication of what API did in my console. From what I have gathered, the R in parallel with the output coupling cap forms an RC filter to help flatten out the bottom end. Also from what I have found, this was first added to the 550 EQ by Wally Heider in the early '70's. Wally hacked in a 47R in parallel with the 400uF coupling cap before the 2503. This RC then started showing up in the output stage of many other API circuits. Typically, there is very little DC offset especially in the ACA or booster circuits. The actual DC voltage at the opamp's output will drop over the parallel R (easy to measure). It is typically less than 80mV so will be even less when it reaches the output transformer's primary (Ohms law). If there is a major problem and you have a spike in DC offset, the 47R will usually smoke due to the uber high current across it so the output trafo will still be protected. Many of the 512C's and EQ's have charred evidence of this burnt 47R.  :)

If you are using something other than an API style 2520 or 1731, I would suggest measuring the DCV after the RC to make sure you don't have anything higher than 80-100mV.

APP992 has an input offset voltage that rarely goes over 15mV and it is however under 25-30mV
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: magnified on March 19, 2015, 03:39:51 PM
Not an electronics genius here, but would it be ok to put a 10k Alps motorized K fader in the place of your 1k fader?

Thanks!

-Joshua
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on March 19, 2015, 03:48:11 PM


 :o
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 19, 2015, 04:37:44 PM
Not an electronics genius here, but would it be ok to put a 10k Alps motorized K fader in the place of your 1k fader?

Thanks!

-Joshua
Yes it should work ok
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: magnified on March 19, 2015, 04:39:06 PM
Sweeet thanks!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: XAXAU on March 20, 2015, 04:16:55 AM
Not an electronics genius here, but would it be ok to put a 10k Alps motorized K fader in the place of your 1k fader?

Thanks!

-Joshua
Yes it should work ok
Will it perform the same as a 1K? Is it just about impedance matching?

Also no electronic genius here! :D
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Humner on March 25, 2015, 01:36:38 AM
Hi Jeff,

How many of the axial Vishay capacitors should I order with my ACABO PCB?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 25, 2015, 09:36:06 AM
Hi Jeff,

How many of the axial Vishay capacitors should I order with my ACABO PCB?
Four of the 470uF's
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Humner on March 27, 2015, 01:13:00 AM
Thank Jeff, I put my order through.

Excited to start playing around with one of these.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: darnell on March 30, 2015, 03:16:35 PM
Hey again,

Got my summing mixer put together, just now hooking up to my lynx out.  I'm wiring stuff up right now and wondering if there may be something that needs addressing. 

So, i've been doing some comparative listening between opamps and seem to be finding that no matter what combo i use, there is a slight high freq roll off going on when i send out a stereo drum track to ch 1/2 on my summing.  Send levels are matched and there isn't anything weird happening aside from cymbal "shimmer" really not being there.  I've been sending a drum bus out Lynx 1/2 and back in to my lynx 1/2 input, which sounds almost exactly the same, and then out Lynx 1/2 to the summing input 1/2 into a 47k resistor on the +side through ch1/2 and out the main outs to the lynx.  I have gar2520 on the ACA board and hardy 990's on channel 1/2 on the main 4ch input board.  In order to have an unbalanced input to my input board, the - on my send from the patchbay to the summing mixer is floated at the db25 on my summing mixer (so basically, i am not attaching anything to the - pin on my db25 that goes to the 2x4 channel inverting ACA input boards.)

I haven't connected any grounds to chassis or tied xlr/db25 to ground and putting a cover on the case def cuts down on noise, but doesn't really help with the high freq loss.   I have Cinemag Cmoq2s outputs on the booster out, and Jeffs 2623-4 PCB transformers on the ACA side. 

Is this an impedance issue? Or do I need to start grounding things and see what works? Or does this summing mixer just inherently roll highs off.   This is my first crack at assembly without some sort of build thread, so please let me know if i missed something obvious.  I can post my comparative audio files and pics if you guys need them.

d.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 30, 2015, 03:21:54 PM
The typical feedback cap in this circuit has a HF rolloff set so its down appx .5dB @ 20k so nothing you would really hear IMHO. I think you should connect your grounds before looking elsewhere.

You might wanna try connecting the - output to ground on the outputs of whatever is feeding the bus R's.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: darnell on March 30, 2015, 04:59:57 PM
What kind of grounding should i be using?

I'm assuming that on the ACA main board, I would tie a star point from where it is labeled "ground" to chassis ground.  That will ground all connections on that board and all boards jumpered off the power "links", correct?  By doing that, i get continuity to chassis from the "ground" point on the ACA board, from pin 1 on both xlr outs and from the db25 ground and - side of the input which are tied together. 

With this setup, it still has a slight rolloff.  In comparison, I can send the same output from the lynx to an old studiomaster board and back into the lynx.  While there is a slightly different color coming back it, the highs stay intact.

I have also tried bypassing the 2x4 ch input boards and just plugging straight from db25 input to the ACA summing section.  Still a little dull.  Would the Cinemags on the output make that big of a difference, of is it probably something else?

d.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: darnell on March 30, 2015, 05:41:39 PM
Jeff,

I tied ground and - together on the db25.  High Freq is restored!!!!  Thanks for the help.

D.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on March 30, 2015, 05:53:36 PM
Jeff,

I tied ground and - together on the db25.  High Freq is restored!!!!  Thanks for the help.

D.
Great, I actually went back to edit my last reply to make that more clear but didn't have the chance to tell you. Glad you got it going!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on April 18, 2015, 02:34:35 AM
Jeff,

I have been looking for a simple, elegant way to sum four channels for live monitors and I think I believe I can do it with this board, but wanted to double check my thinking before I began. I'm looking to sum four channels, a left and right (stereo) and two mono sources, (artist vocal and instrument). Can I do this passively and then use the booster side of the 2-ACA or do I need to run each source into your 4 channel inverting summing PCB and then the booster? At some point I would have to "Y" the mono sources to both the left and right sides. Everything is going to go in a single rack space chassis that will be just a power button and XLR in and out. No switches, knobs, or faders as the mixing levels will be performed by whatever is feeding the summing PCB. I'm trying to figure the best way to do this while taking into consideration all the relevant audio jargon.

Also, I would like to build an 8 or 16 channel version for my studio later this year. I'd love to hear what the difference would be of a real API summing mixer over my SPL Mixdream XP. I have bunch of op amps I've built that I need to do something with.

Thanks!

Paul

Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 18, 2015, 10:11:46 AM
Paul, you would not need the INV PCB for this, just the 2-ACA-Bo.

Are the device that will be feeding the inputs balanced or unbalanced?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on April 18, 2015, 10:29:08 AM
Actually Paul, if you don't need the insert point or master fader, you could do this by only populating 2 channels of the INV-ACA board. In addition you would need 2 off board output transformers.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on April 18, 2015, 10:43:55 AM
Jeff,

It would be balanced. The Left and Right would be coming from a console and the mono channels from some sort of channel strip. It would be feeding an wireless in ear monitor transmitter and also return back to the console for the monitor engineer to cue it.

I'll order the parts next week. This is very exciting!

Thanks!

Paul
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Eliani on May 15, 2015, 06:02:03 AM
I've been reading this thread for the last few days and still only made it through half of it. I just couldn't hold myself any longer so I thought I get a head-start, post my current questions and read the rest of the thread later today. If I happen to grasp what I need to do before anyone willingly answers my questions I'll take the hit and die a graceful death!! As a reference to what else I'm doing to my console here's my thread: Another TAC Scorpion overhaul (http://groupdiy.com/index.php?topic=59170.0), where I've used 2520 based differential line-drivers to replace the original pre-amps.

To implement the 2-aca-bo in my little scorpion I consulted with Mitsos, as he installed one in his TAC Scorpion too. I got this little hookup circuit from him. This image represents the S4000 master mix-bus and fader booster. This seems right to me besides he doesn't use the balancing and inverting 2623-4 output I guess, for this wiring schematics uses the original insert-point. I rather use the 2-ACA-Bo as designed and do as little damage to the original circuit. I Rather leave it as is so I can easily revert the output stages to the original.

(http://groupdiy.com/index.php?action=dlattach;topic=59170.0;attach=34473;image)


The S1000 input channels have 10k summing resistors and from what I've read in this thread I would get away with replacing Rf with 6.2k and Cf with 150pF. Although I did not check this myself, maybe it's better to do so and at least understand what I'm about to do. There's a link to a resistor calculator somewhere in the first few pages, but that doesn't lead me anywhere...

I would be rather pleased with anyone confirming or helping me with errors on this attack-plan...

EDIT:
So to calculate Rf (feedback resistor) I would need to multiply the desired gain with the value of the summing resistors? Then how do I know what Gain value I need to bring the summing amplifier towards -.5dB?

Original setup: Rf=28k, Rs=47k Gain=Rf/Rs=0.59
Scorpion setup: Rf=?, Rs=10k Gain=0.59 Rf=Gain * Rs=5.96k
With a 6.81k (That's what I've got for now) I get a 0.68 gain (is this -0.68dB?)
I've left the 47pF in there for now, but still looking for the right way to calculate it's value...

So I've got it working so far, with a slightly off gain setting, no calculation for the feedback capacitor, and not so logarithmic behaving fader... But at least I don't have to die that graceful death just yet!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jonbstevens on May 22, 2015, 02:47:01 AM
Thanks Jeff for this great project. Last week I finished installing the 2-ACA-bo in place of the master section in my Soundcraft 200b -- everything works and sounds great, the only change I made was the feedback resistors and capacitors as the Soundcraft uses 22k summing resistors. 

Not content to stop there I'd like to replace the mixers 4 buses with 2-ACA-bo boards but i'm a little unsure of how to connect the ACA-bo which replaces the bus into the ACA-bo on the master fader.  I like the idea of having some extra gain on the bus outputs to drive the input of the Master ACA even harder, so I'm wondering if it's wise to take the booster output on the BUS ACA-bo and run those through 22k summing resistors into the master ACA-bo? Or am I better off using the -6db Booster output from the BUS ACA-bo and feeding that into the master ACA-bo via summing resistors?

Any advice would be greatly appreciated. Thanks!
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 04, 2015, 12:29:44 AM
Jeff,

So I've finally  acquired all the parts I need to build a simple summing mixer with the INV ACA minus a case and some VU meters (I read on the Interwebs that it had to have meters or it wasn't cool). But before I fire up the iron I wanted to see if there was a simpler way to do what I wanted to accomplish before I cast myself headlong into this project. As stated in my previous post, I'm building a box that allows me to mix a vocal from a channel strip with a stereo mix from a monitor console, allowing me to keep the vocal chain purely in the analog domain (minus the RF transmission) minimizing any latency with in ear monitors that creates a disconnect between a singer's vocal and their chest resonance. In the past I would just use a separate mixer, but that is always way over kill since I just need something that does four inputs maximum.

I was going to take the vocal signal and "Y" it to a pair of the INV ACA channels and then add the left and right signals from the monitor console (minus vocal) to their respective sides of that same pair. But I'm afraid that the split vocal signal would actually tie the LR channels of the ACA together and effectively give me two mono summed outputs. So where I've landed is to split the vocal to channels 1 and 3, the LR mix to 2 and 4, then use the JP points to merge 1 with 2 and 3 with 4. Obviously this means building the entire INV ACA board, which I don't mind doing, but my limited knowledge is preventing me with coming and understanding a simpler way to accomplish my goals. I just want to make sure that whatever I do the output is a stereo mix with vocal down the
center.

Also, since all the lines going in are balanced, would it be best to use a transformer to do the unbalancing or just tie the "-" with the ground and that be good enough.

Lastly, if I use capacitors with higher voltage ratings than what is on the BOM, could I run this at 24V? The op amps I have picked out for this can handle as high as +/-25V.

I'll post pics when done.

You and your products are super mega awesome. I'll have you a minimum of one beer next time both of us are in Nashville.

Thanks!

Paul
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 04, 2015, 11:39:04 AM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 18, 2015, 08:49:41 PM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 18, 2015, 09:19:17 PM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 19, 2015, 09:32:29 AM
Correction, it is the EA2623-1 transformer and not the 2622.

Paul
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on June 19, 2015, 10:25:08 AM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 22, 2015, 06:10:13 PM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 22, 2015, 06:10:38 PM
One more pic.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Potato Cakes on June 22, 2015, 09:36:10 PM
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
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: kante1603 on June 23, 2015, 12:41:20 AM
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.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: JW on July 06, 2015, 04:05:31 PM
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?
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: jsteiger on July 06, 2015, 06:03:28 PM
Yes this sounds like the way to go. You should not need any other boards.
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: XAXAU on July 10, 2015, 10:03:27 AM
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! :)
Title: Re: [BUILD] classicapi.com *2-ACA-Bo* Official Support Thread
Post by: Gwen on August 25, 2015, 06:20:05 AM
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



Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: coldwar on September 26, 2015, 01:32:28 PM
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?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on September 26, 2015, 10:20:01 PM
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
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: coldwar on September 29, 2015, 11:19:46 AM
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?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on September 29, 2015, 11:38:07 AM
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.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: coldwar on September 29, 2015, 12:47:03 PM
gotcha!  already swapped opamps same result looks like we will be checking of those cold joints.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on September 29, 2015, 01:06:07 PM
Did you swap your "insert" or fader wiring between channels?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: coldwar on September 29, 2015, 02:41:38 PM
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?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: ilfungo on October 13, 2015, 07:28:05 AM
Hi to all!
I've just ended my Aca booster board with APP 992 Doa and need some help...
I want to use the Aca as alternative master for my Amek M2000 board ( 47k summing resistor as API console).
On Amek There are 2  - Summing board GL80C
I just nedd to patch the Aca Boster in same place of GL80C?
Thanks!!!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on October 13, 2015, 10:36:44 AM
Yes it appears that way.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: ilfungo on October 13, 2015, 01:35:31 PM
Sorry,  if I want to build a completely new master, where I can find some info about a possibly monitor section and aux input (some for Daw L/R Master )?
All the suggestions are welcome!
THANKS!!!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: fragletrollet on October 15, 2015, 02:50:54 PM
A question about the 2S-LA: how much gain can it be setup to give? I`m planning to use it as makeupgain for a couple of line-units.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on October 15, 2015, 02:57:14 PM
A question about the 2S-LA: how much gain can it be setup to give? I`m planning to use it as makeupgain for a couple of line-units.
How much do you need? I have never experimented with max gain but it should be capable of an easy 40 if need be.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: fragletrollet on October 15, 2015, 04:08:51 PM
That is more than enough! I`m going to use them as makeup-gain for some boutique guitar-pedals I intend to inject into my modular synthesizer. So I was planning to use them without transformers, merely as line-boosters. No need of  balancing the signal. The guitar pedals have a line outputs, so I was planning to use the 2s-la without transformers, just for gain control. So I just wire it up with an attenuator in between the stages?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: fragletrollet on October 15, 2015, 04:37:32 PM
and what power is it expecting?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on October 15, 2015, 06:05:29 PM
...So I just wire it up with an attenuator in between the stages?
Yes that should work. Just a pot or fader. The card uses 2520 style opamps so +/-16VDC.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: stuartpre on January 10, 2016, 02:28:31 AM
Hi,
I've build and mounted the CAPI Mixbuss in my Yamaha m1516.

Now I need to decide how I am going to power it?

The Yamaha has +_ 25 vdc rails for audio.

What is the max safe operating voltages for the CAPI mixbus?

Do I just drop the +-25vdc through some diodes to the safe operating voltage of the 2520's, +- 20v dc??

10 diodes for each rail?

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Humner on January 10, 2016, 04:20:21 AM
I would assume its depends on the opamps used. If you are using Yamaha NE80200 then you can supply the CAPI board with that voltage feed, provided you use 35v caps where appropriate.

Otherwise you should find the m1516 also supplies -+16v voltage from its PSU as well, as the EQ section of the m1516 are using DIP8 opamps. So use this voltage feed if you are using DOA's which are happier under -+20v...
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 10, 2016, 10:37:52 AM
Yes it mainly depends on the opamps used on the 2-ACA-Bo board. There is not much to gain by running 2520 style DOA's beyond 16V.

Keep in mind the voltage of the PSU caps used on the 2-ACA-Bo. IIRC, 47µf/25V are in the BOM. They should be ok for 24V use but if it were me, I would increase them to 35V parts.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: r2d2 on January 13, 2016, 09:42:17 AM
....same , but different diy layout of original Api Summ "set" )
as in image?

r
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 13, 2016, 10:22:09 AM
....same , but different diy layout of original Api Summ "set" )
as in image?
That is not DIY but products from API. They are discontinued now.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Guitardude57 on January 16, 2016, 05:34:20 PM
Hi all!

I am considering building up an ACA-BO and a 32 channel summer, and a way to get audio out of my DAW.. into the analog world, and back into the DAW.
There will be times when I will only used 4-8 sums, and most often none...  maybe a switch network to cut off unused inputs, with different resistor values switched in and out?

At this point, the summing will be secondary to having an analog stereo set coming out of the DAW, with some inserts, and a stereo fader to go back to a A/D converter, back into the DAW.

Has anyone done a table top set up with the ACA-BO using db 25 sum ins/outs as well as insert jacks, meters, and a fader, etc?

This will be used primarily for Mastering.

Any thoughts, or ideas welcome.  I would like to start this sooner, rather than later.


Peace,

Mike
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: stuartpre on January 18, 2016, 02:44:33 AM
Hi Jeff,

I have powered up for the first time. No smoke. But no audio. All I have is a high frequency oscillation, which the faders seem to modulate up and down a bit.

I ended up providing the +- 16v by making up a little board using two 16v zeners, some resisters and caps, as per the Yamaha m1516 schematic (for eq section).  I tested the power supply prior to connection to the API board.

I used the existing pair of 10K faders, I just de-soldered the existing wire and individually shrink wrapped them to prevent any shorts.

Also I broke the Buss jumpers on Master (Program 1 and 2) boards 1 and 2 so no signal is going to the old master section. I then took my LR feed from the Master board 1 (where the jumpers can be, but are not now) I did remove one ceramic cap from the old master section so as to use one of the pcb pin holes which goes to earth. This was my shield point for the feed to ACA input.

The outputs of the new booster amp I wired up directly to the existing xlr outputs for program 1 and 2 (Main buss). I made sure to remove the old connections and again shrink wrap them individually.

Finally I connected the mute input to an earth point on the API board (as advised on the schematic), I choose the shield input of T/B as it was available.

I have measured the DC voltages at the input DC on the CAPI board. That is wrong for sure. around +-7vdc, should be +-16vdc. I have measured the voltage feeding the zener board and it is as it should be at +-25vdc. I measured the output of the zener board as +-16vdc  (correct) before i attached the CAPI board. But now it is wrong.??

I have now disconnected the Zener +-16vdc board and tested the unloaded voltage. It is once again correct at +-16vdc. 

Schematic for Yamaha m1516:

http://elektrotanya.com/yamaha_m1516.pdf/download.html

Could someone please have a look at the resisters in the +- 16 zener distribution? Do I need to change these based on the current usage of the CAPI? I have 4 x GAR2520 installed.  An6522 x 1.5 vs Ga2520 x 4,   current difference?

Or should I build a separate +-16vdc power supply for the CAPI board? I have a build JLM ACDC, i just need a transformer and stick it in a box. Will this lead to hum issues?

Thanks
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 18, 2016, 12:02:45 PM
Sounds like a PSU issue. I couldn't see the zener schemo but can only imagine that the series R's would need to be adjusted for current draw. I don't know if this is the best solution for powering a master summing circuit.

Also, have you tested all of the opamps in something so you know they are working?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: stuartpre on January 18, 2016, 10:18:21 PM
Good Idea Jeff.

I tested all 4 Gar2520 in my VP312, all working fine.

So If I go ahead now and build a dedicated power supply for the ACA-BO, are there any special earthing considerations?

Should I tie the ov to chassis of the console and do the same with the earth point on the ACA-BO?

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 19, 2016, 10:20:02 AM
Good Idea Jeff.

I tested all 4 Gar2520 in my VP312, all working fine.

So If I go ahead now and build a dedicated power supply for the ACA-BO, are there any special earthing considerations?

Should I tie the ov to chassis of the console and do the same with the earth point on the ACA-BO?
I am not sure how the grounding scheme is carried out with your board. It may take some experimentation to get the most quiet grounding scheme with the 2nd PSU.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: stuartpre on January 19, 2016, 06:22:05 PM
Well all modules have a fat green wire and/or an aluminum mounting bracket that run to an aluminum cross member. One member for the channels and one member for the master section. These alluminum members have a fat green wire running back to the rear panel and mount a screw located about one inch from the power distribution, a small 3 by 2 pcb that is mounted to the rear panel via a strip of angle copper. So if I earth my additional power supply at the same point and run a fat green wire from earth of the CAPI board to the same rear panel earth, then finger crossed?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 19, 2016, 08:07:02 PM
Well all modules have a fat green wire and/or an aluminum mounting bracket that run to an aluminum cross member. One member for the channels and one member for the master section. These alluminum members have a fat green wire running back to the rear panel and mount a screw located about one inch from the power distribution, a small 3 by 2 pcb that is mounted to the rear panel via a strip of angle copper. So if I earth my additional power supply at the same point and run a fat green wire from earth of the CAPI board to the same rear panel earth, then finger crossed?
You can start that way and see how it performs. You may want to connect the shield for the main bus feeds to the bus bar that the consoles master section uses.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: stuartpre on January 22, 2016, 12:14:33 AM
Hi, It now works but has hum. After much trial and error I found that when I disconnected the inputs from the buss the hum and noise disappeared.

I had found a point on the old master module where the L R buss (1 2 ) entred and disconnected that from the cct. But as I said it did not work. How do people usually go about tapping the buss? Should I take the feed after the buss resistor on an input module instead? How important is shielding at this point? Must L and R be independently shielded?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on January 22, 2016, 10:07:31 AM
Hi, It now works but has hum. After much trial and error I found that when I disconnected the inputs from the buss the hum and noise disappeared.
This sounds like a ground issue of some sort.

Quote
I had found a point on the old master module where the L R buss (1 2 ) entred and disconnected that from the cct. But as I said it did not work. How do people usually go about tapping the buss? Should I take the feed after the buss resistor on an input module instead? How important is shielding at this point? Must L and R be independently shielded?
I am not sure how your console is but if there is a backplane, you should be able to just tap into the L/R bus tracks somewhere near the mid point of all of the channels. This will be basically right after the channels bus R's. I would keep the L/R cables separate if possible and shield them.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Drumbreak on March 04, 2016, 05:18:33 PM
Hello,
To Jeff, or anyone else who has the knowledge:
I have a Trident Trimix which I want to add this board to.  My question is about the bus resistors.  On my board, the pan outputs feed all the buses and mix bus with 12k resistors.  Can I just swap those out with 47k for the ACA or should I modify the ACA itself?  And if so, I know how to solder and follow instructions, but I don't know the math to adjust the R C values...a little help in that direction would be awesome!  Also, the Trident supply runs on 18v, which should be good for all the DIY DOAs out there (planning on building some 990s), but how will that affect headroom/ response?  I imagine it will be better than the three TLO 71s the trident uses in it's summing blocks...
Thanks,
Brendan
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on March 05, 2016, 10:30:56 AM
Hello,
To Jeff, or anyone else who has the knowledge:
I have a Trident Trimix which I want to add this board to.  My question is about the bus resistors.  On my board, the pan outputs feed all the buses and mix bus with 12k resistors.  Can I just swap those out with 47k for the ACA or should I modify the ACA itself?  And if so, I know how to solder and follow instructions, but I don't know the math to adjust the R C values...a little help in that direction would be awesome!  Also, the Trident supply runs on 18v, which should be good for all the DIY DOAs out there (planning on building some 990s), but how will that affect headroom/ response?  I imagine it will be better than the three TLO 71s the trident uses in it's summing blocks...
Thanks,
Brendan
I would not recommend changing the bus R's. Just adjust the feedback R's on the ACA section of the 2-ACA-Bo. For 12k I would go with 7k15 and 200pF or 220pF for the feedback cap. The increase in voltage rails will slightly increase headroom but its negligible.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Drumbreak on March 05, 2016, 07:31:43 PM
Cool, thanks Jeff!
Cheers!
Brendan
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Drumbreak on June 25, 2016, 05:39:35 PM
Ok, so I've got the ACA up and running and it sounds great!  Well, out of the main outputs...
My problem now is integrating the new ACA into the monitoring path of my board.  When I take the signal off the + side of the Booster Out Mult, it sounds like the whole frequency response is shifted up: it has no low end above about 200 and the high end is piercing and noisy.  My uneducated guess is that there's a impedance mismatch happening between the ACA and the monitor amp section...?
The ACA replaces a similar circuit in my master section that uses two TL071s for summing amps and another as a post fader booster.  What's now missing in the new ACA is the monitor buffer and line amp.  The buffer, which mults right off the main XLR output is a TL071 at unity gain followed by a TL071 that adds gain (6db, I think) and feeds the monitor section which, surprise! is a few TL071s...I should mention that the whole internal busing in the Trimix is unbalanced and I might not be making the proper connection by just feeding the monitor bus with the + side of the Main Out, but that's my understanding of the unbalanced input of the internal bus.  The solution I'm thinking is to make a small board that replicates the monitor buffer circuit as is done in the original master section, but I'm hoping that's not necessary- there was plenty of gain in the monitors, it just sounded sh*tty.  Do I need a bus resistor?  The original buffer has a 12K feeding the output to the monitor amp.
Thank you all for your time and help!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: punk on September 26, 2016, 11:42:57 PM
just getting around to building this. My fader is 5k, so what value should I use for R1 and R5?

byron
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: critterkllr on October 19, 2016, 04:50:37 PM
I'm running into a problem when I installed this in my TAC Scorpion II. I only have the ACA section hooked up right now for summing. The left side is much louder and the right side is much quieter than it should be. I've swapped in 6 different opamps with the same results. The low end is completely gone as well. It sounds like a high pass at about 500hz.

My PSU is +\-17V, but a DMM reads +16V -17v at the pcb.

Not sure where else to go here. I've spent around 11 hours checking the wiring and component placement over and over. No cold solder joints.

Both sides are unbalanced with the + connected, shield connected at one end, and the - disconnected.

Feedback resistors and caps changed to 5.9k and 220pf to work with the 10k summing resistors.

I've verified that it is the summing stage by recording directly from an insert (before the monitor section).


EDIT:  The strangest thing is happening. When I connect the negative out of the right ACA to ground, the left side of the stereo tracks goes to normal volume and the right side gets really loud. It no longer has a big lack of low end.

Connecting the negative left ACA out to ground makes no difference  is right is already connected. If it is not, then it lowers the volume of the left channel to be correct, but the right stays small.

I'm also noticing with this latest update that panning works in the opposite direction than it should, but it is definitely wired correctly on the left and right sides.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Humner on October 21, 2016, 03:31:40 AM
Are you sure you don't have any shorts?

I remember when I finished my ACA-BO and found I was frying one of the 10ohm power resistors because I had a solder bridge on one of the 47uf caps (that come after the 10ohm resistors). I remember the pads for the 47uf caps being quite close, so a solder bridge shorting one(or more) power rails to GND is a possibility. The 10ohm resistor was doing its job (otherwise I may have fried my opamps/PSU instead!).

It could be that you have fried one of the resistors the first time powering it up and didn't notice and now the error continues?

Eitherway, check your 10ohm resistors, look for any black soot to indicate its been fried(but also check the resistors, with a multimeter). if you find one then check your soldering for you 47uf caps.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: yosh on October 31, 2016, 05:49:04 PM
Hi,

I just bought a Speck M72 line level console and I'm working on a switchable summing design using inverting ACAs and the 2 ACA BO. I'm hoping to do API, Jensen and Neve style summing on a 2 pole 3 way switch. I'll be making a new master front panel with the three faders and switch which will go next to the existing master section which I will still use for the Aux returns, and Bus 1-16 outs. I have questions about how to get the right impedance for the Neves, but I'll post in a different thread with those questions. I've attached a diagram of what I'm thinking. Just wanted to run it by some people to make sure that I'm on the right track. Thanks!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Fsharpminor on November 01, 2016, 02:41:00 AM
I am very interested in this as well!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: JW on December 04, 2016, 02:16:08 PM
Hi Jeff,

I really appreciate you continuing to check in on this thread. I installed the ACA buss into a 32 channel Yamaha PM2000 console. It sounds great but. . .

I'm noticing after using it for a while that I'd like more gain. I'm summing 32 (actually only loaded with 24 right now) through 33K buss resistors.

Here's your recommendation for the feedback resistors and caps for my situation, quoted from back on page 11:

"I get 19660 ohms for feedback R so I'd use a 19k6 which is a standard value. Yes, 68pF for the feedback caps C11 and C15. You only need to change R10 and R13. Leave R9 and R12 as they are.

Cheers, Jeff"

Anyway, I'm finding that there's a few occasions that I'm having to push my inputs too hard to get the level I want on the final 2 track. I've returned to using my console's original output busses because the increased output level allows me to have my input strips down one more click which makes the total sound a little less pinched sounding. I attached a schematic of my Yamaha PM2000 output buss for reference.

My question is this. Would changing the feedback caps/resistors be a good way to get (an estimated 3-6 dB) more gain?

Or is this the whole reason that the inverting ACA board was created in the first place? Perhaps this is what I need.

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on December 07, 2016, 02:44:05 PM
You can temporarily put a trimmer in place of the feedback R to get the level up where you want it. Pull the trimmer and measure. The feedback cap should then be adjusted for a similar rolloff as stock.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Whoops on December 10, 2016, 02:00:26 PM
Hi Jeff and fellow members.

I have an Alice 828 mixer that I really like although I would love to implement a Discrete summing section and balanced output with transformers.

The desk has 8 channels plus 1 stereo echo return and summing is done originally with 33k resistors, then the Master has a really cool Stereo Limiter, Master fader, makeup gain with IC and unbalanced out.

Could you please help me out on how I could incorporate the 2 ACA BO circuit in this layout while maintaining the Limiter?
I would like to replace the original summing to API style and get rid of everything in the Master section with the exception of the Limiter Circuit.



here is the schematic:

(http://i1124.photobucket.com/albums/l579/ilcaccillo/Alice%20828%20Summing%20schematic.png)

thank you so much for your help and guidance.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Whoops on December 11, 2016, 07:43:48 AM
Can I get rid of IC1 or it's part of the Limiter Circuit?

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: JW on December 11, 2016, 05:04:21 PM
Thanks Jeff,

I used a pot for the feedback resistor to get the level where I want,  I'm getting 44.2K for the feedback resistor.  (Had a 19.6K in there prior)

I have a 68pF cap in there now, which was in conjunction with the prior 19.6K feedback resistor.

What's the feedback cap size I need for the proper roll off?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Humner on December 11, 2016, 06:03:22 PM
30pf should keep it in the same range which is ~120khz
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: JW on December 11, 2016, 07:12:10 PM
Thanks Humner!

Where is the calculation you're referencing? Page 7 had a calculator from somebody named Bicycle Bob, but that link is gone.

Also, I'm guessing it's gonna be 27pF or 33pF. Haven't gone looking for caps yet though.

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Humner on December 11, 2016, 10:18:56 PM
Thanks Humner!

Where is the calculation you're referencing? Page 7 had a calculator from somebody named Bicycle Bob, but that link is gone.

Also, I'm guessing it's gonna be 27pF or 33pF. Haven't gone looking for caps yet though.

I use this - http://www.muzique.com/schem/filter.htm

So you punch in

44000 ohms
0.00003uf (30pf)

And then it gives you the corner frequency. For some reason that calculator doesn't like determining the capacitor value, so I just get things in a ball park and go from there.

You can check the frequency with either 0.000027 uf and 0.000033 uf  to see the results from those PF caps you have access to and decide which way to go, but either will do fine.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on February 26, 2017, 10:58:12 PM
Hello,

I'm using the CAPI ACA & Booster on my summing system. I'm having the ACA feed a patchbay and return into the Booster side, but with no master fader. I just want to be able to insert a buss compressor there. Do I have to change anything if I skip the master fader?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on February 27, 2017, 10:10:48 AM
Hello,

I'm using the CAPI ACA & Booster on my summing system. I'm having the ACA feed a patchbay and return into the Booster side, but with no master fader. I just want to be able to insert a buss compressor there. Do I have to change anything if I skip the master fader?
You can just put a 1k shunt R to ground where the fader would be.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on March 01, 2017, 11:21:32 PM
Thanks, Jeff.

Another question for the community? In the spirit of using some parts I already own, I have a bunch of new Jensen JT-112-LPC line output transformers. I was thinking of using them on the output of the right side of the card (ACA outs). This is feeding my patchbay to provide and insert point for stereo buss compression/processing. Here is a link to the specs:
https://www.yumpu.com/en/document/view/22838301/jt-112-lpc-jensen-transformers (https://www.yumpu.com/en/document/view/22838301/jt-112-lpc-jensen-transformers)
These should work well. Or, can anyone see a potential problem with them? Thanks.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on March 02, 2017, 12:37:03 AM
Looks like those should be fine. Give them a try and see!!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Potato Cakes on March 11, 2017, 03:20:32 AM
Hello, everyone.

I made another one of the 3:2 versions for IEM mixing for another monitor engineer friend of mine, except this time it was requested to have 2 channels with panning and a stereo pair feeding two sets of outputs. I used 4 differential input boards from DIYRE with INA137's. For the panned inputs, I took those to a DPDT switch so I could select between mono (bypass pan knob) or stereo pan. The poteniometer is a 10k linear with center detent that I got from Jeff. I would like to find a little beefier pot as this one has solder pins that require some care when handling. But that's what I had and the Bourns pots do feel nice. With the switch at mono position, it splits with the prescribed 47k bus resistors to sum with the stereo input. With the switch at the stereo pan position it feeds the pan knob with the signal split across two resistors as shown in the Orban panning schematic. The values I landed on are 10k to feed the wipers and 15k as the bus resistors that sum with the stereo input. I started off incorrectly as I misplaced in my head where the 10k resistors in the schematic were, and I didn't actually know this till I started typing this. Even so, it does work as expected.

Thanks!

Paul
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Potato Cakes on March 11, 2017, 03:22:33 AM
And the unit itself.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on March 26, 2017, 02:21:55 PM
Hello,
I'm using CAPI's passive panner feeding my ACA card. I've wired the panner as per Jeff's recommendations off the CAPI site:
http://www.capi-gear.com/catalog/images/gallery/pots/BI/Passive-pan-pot-network.pdf (http://www.capi-gear.com/catalog/images/gallery/pots/BI/Passive-pan-pot-network.pdf)
I'm using 2k2 resistors in the RS position. According to the notes, this should get me a -4.5dB pan law, but I'm getting an almost 7dB drop at center. If I change the RS resistors to 4k7 ohm, I get about a 6dB drop. Wracking my brain here.  Can anyone shed some light on this? Thank you.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on March 26, 2017, 02:47:23 PM
It may have something to do with the value of Bus R's (if they are dif) or whatever you are feeding the pan network from. There will be some interaction so adjustments may need to be made. Its easy enough to try with no slug R's to verify and then just adjust the slug R until you get the pan law drop you want based on your exact circuit.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on March 27, 2017, 01:50:07 PM
Jeff,

I'm coming out of my pro tools interface (mytek 8x192) as a temp source. Feeding + into the pan, - and shield (ground) to the panner's ground. When you mention Slug R, are you referring to RS on your schematic? Currently, I'm using your pan pot,  RB = 47k, RL =3k3.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on March 27, 2017, 02:05:27 PM
Jeff,

I'm coming out of my pro tools interface (mytek 8x192) as a temp source. Feeding + into the pan, - and shield (ground) to the panner's ground. When you mention Slug R, are you referring to RS on your schematic? Currently, I'm using your pan pot,  RB = 47k, RL =3k3.
Yes Slug R = RS. It may have something to do with unbalancing the Mytek outputs. I would not bank on this if you are changing the source. I saw "temp source".
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on April 17, 2017, 08:16:38 PM
I have two Cinemag CT-2385 line output transformers.  They looks just like the output transformers from the CAPI store and fit on the Booster board. Can any of you pros have a look and see if the color code match between the Cinemag and the CAPI Booster output section? Thanks for the help.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on April 17, 2017, 09:58:41 PM
I have two Cinemag CT-2385 line output transformers.  They looks just like the output transformers from the CAPI store and fit on the Booster board. Can any of you pros have a look and see if the color code match between the Cinemag and the CAPI Booster output section? Thanks for the help.
http://www.capi-gear.com/catalog/images/gallery/2503/2503-specs.pdf
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: supafuzz99 on May 15, 2017, 09:25:49 PM
I have a 1974 Allen & Heath Mod 2 that has 8 output busses
that I mix into protools. I would like to be able to get more headroom by adding line amps with output transformers for each of the 8 busses the busses go into seperate channels of lynx aurora and get summed  in protools. This way I can compress each channel differently with outboard.

So what would I need to do this?
2 capi's?or 4
or do i just need booster amps?

I am electronically challenged so please bear with my confusion.

thanks

Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on May 16, 2017, 10:36:19 AM
If you do not plan on replacing the summing amps in your board then it sounds like just a single stage line amp would work for you.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: madbeavis on May 19, 2017, 03:03:50 PM
Hello all,

 I am trying to re purpose the Classic 2-ACA-Bo Rev B.1 into a simplified 536 input module replacement. I read on this thread that several traces would need to be cut on the ACA side. The difference in the schematic is clear but im not sure if I should just leaving those thruholes unpopulated or actually cut the traces. From what I can tell this is only needed on the ACA side, the booster side appears to be similar to the 536 already. If anyone has attempted this before please let me know.

Thanks,

Chris
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Sinkia on July 20, 2017, 09:23:18 AM
Hi everybody !

I just have finish my 2-ACA, and after several testing, it appears I do have one side with ground noise, and the same side is distording too..

It seems to be a grounding issue, but I don't really know where it could be wrong...

Any ideas..?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on July 20, 2017, 10:45:04 AM
Hi everybody !

I just have finish my 2-ACA, and after several testing, it appears I do have one side with ground noise, and the same side is distording too..

It seems to be a grounding issue, but I don't really know where it could be wrong...

Any ideas..?
Have you ruled out opamps? You can swap left for right to see if the problem follows. You can also do the same for the wiring to and from the board to see if the fault is truly on the ACA card. You can next isolate if it is within the ACA section or the Booster section the same way.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Sinkia on July 20, 2017, 11:45:34 AM
Have you ruled out opamps? You can swap left for right to see if the problem follows. You can also do the same for the wiring to and from the board to see if the fault is truly on the ACA card. You can next isolate if it is within the ACA section or the Booster section the same way.

I already have swap the op amp in it, but still have the same issue.. I will keep looking on tomorrow... I'll come back here on tomorrow to let you know!
Many thanks for your help !!! Jsteiger
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Sinkia on July 20, 2017, 03:14:29 PM
Atention - Weird -

So I made a couple test and here are my result :

The summing do not have any noise when nothing is plugged in. slightly a reaaaaaaally small noise like Voltage issue that we an ear.

Here is the main point : I have plus my mpc straight into the sub d input of the summing. no noise, no distortion, everything is smooth.

then  have plug my digi HD interface in it, and here it happen again.
I guess it all come from the 192... seems weird no? cause it do nt distort when I plug in other gears..
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Sinkia on July 20, 2017, 03:31:22 PM
INVESTIGATION - PART 2 :  8)

So I'm checking the calibration of my 192, eveything is great. there's a slightly 0,5 db less on one output, but otherwse, everything works as it should be..

I arrive with different question now :

- How many 47k resistor h-should there be in the signal pass? I mean, when this s a line lvl conneced, everything is smooth and go as it should be, but when this is the otut of my interface.. BADABOOM

So here is my question :

IN 1-16 -> 47k bus resistor -> INPUT L/R ACA 

ORRRRRRRR

IN 1-16 -> 47k bus resistor -> 47k bus (L&R busses) -> INPUT L:R ACA?

My question seems stupid, but we doin't know.. what bother me is that everything works fine with the MPC...
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on July 20, 2017, 08:36:16 PM
It may be easier to understand a quick sketch rather than your circuit description.

Its possible that the 192 does not like being unbalanced? Maybe using an INA134 as a unity gain balanced to unbalanced receiver might be a better solution.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Sinkia on July 22, 2017, 06:26:53 PM
It may be easier to understand a quick sketch rather than your circuit description.

Its possible that the 192 does not like being unbalanced? Maybe using an INA134 as a unity gain balanced to unbalanced receiver might be a better solution.
I'm not really into It This week, but i'll have à Closer look on next week and come back here..!
Many thanks for you help!!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Paul Tong on August 02, 2017, 02:44:29 PM
Hi Guys! I would like some help trouble shooting.
I finished building the 2 Channel ACA & Booster.
I tested the output of both channels going onto a RME FF800 interface.
the right side is very quiet but the left side is hissing, even when there is no input.
I have shorted the talk back FET. Still the same. is it suppose to hiss due to aplification?
Should I use 28K ohm for feed back? please help.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on August 02, 2017, 10:38:00 PM
Hi Guys! I would like some help trouble shooting.
I finished building the 2 Channel ACA & Booster.
I tested the output of both channels going onto a RME FF800 interface.
the right side is very quiet but the left side is hissing, even when there is no input.
I have shorted the talk back FET. Still the same. is it suppose to hiss due to aplification?
Should I use 28K ohm for feed back? please help.
There should generally be very little noise and both stereo channels should behave the same.

When you say "left side" do you mean the 2 left channels on the PCB which are L/R ACA's or do you mean the 2-stage Left channel circuit as opposed to the 2-stage Right channel?

Either way, the very first thing to do would be rule out opamps...if they were built from kits.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Paul Tong on August 02, 2017, 11:39:43 PM
ok let me recheck the opamps.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: orangerec on August 09, 2017, 02:17:11 PM
Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on August 09, 2017, 02:27:16 PM
Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks
What is the part # and how are you measuring? I don't think they made a 4k fader.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on August 10, 2017, 12:38:31 PM
Hi guys,

I'm building the CAPI ACA card. I'm utilizing a stereo Penny  & Giles fader between the ACA and Booster side. I've measured the fader and it reads 4k ohms. Jeff or anyone, can you tell me what value resistors to use in R1 and R5 on the Booster side?

Thanks
Per the pics you emailed me, the P&G part # is 1122C. The "C" designates a  5k value. That said, I think you are fine using the R's suggested for a 10k fader.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: grahamsound on October 05, 2017, 10:40:29 PM
Hi Jeffrey and all,

I just ordered the ACA-BO, and I have a few questions.  Thanks for indulging me.

I have read this entire thread, and gleaned lots of good information.  To help myself and others learn, it might be nice to write out a more conceptual, step by step overview of upgrading the Summing Buss in a mid level console:

Soundtracs Topaz

Topaz Power Supply is +/-17V, and I just totally rebuilt it.  I'm hoping there wont be a problem with using it to power the ACA-BO.  It is rated 1.5 Amps for 24 channel and 2.3 Amps for 32 channel.  Thoughts?

Looking at the channel LR assign section on the input PCB schematic, I appears the Topaz's buss resistors are 22K.

As per your suggestions on this Build Thread, with 22k bus R's, I will change R10 and R13 from 28K to 13K, and C11 and C15 from 47pF to 100pF.

Wiring-wise, as far as I can tell, I want to grab the Left Buss and Right Buss signal off the ribbon cable at the Submaster PCB.  This will be after the console's 22k summing resistors, but before the master sections insert driver, insert, fader, and fader driver.  Is there a best technique for patching in to a ribbon cable?  Or is it better to get it from the PCB somewhere?

I still want to use the other features of the master section like Control Room, Studio and Headphone outs.  I assume this is where the Mult out on the Booster section comes in to play?

Is the best practice to wire ACA-BO Booster Main outs directly to the LR output jack, and wire Booster Mult outs back to LR circuit after the now-bypassed Topaz fader amp?

Additionally, what are common applications for the ACA stage Mult Outs, if any?

Thanks for your time.

Graham
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on October 18, 2017, 12:10:13 AM
Possibly a stupid question but one I thought I’d ask before proceeding...

The + and - sides of both the ACA and Booster outputs are shorting together, is this a bad sign?

I’ve got my board stuffed and installed in a Soundcraft 200b and noticed this as I begun wiring it in.
Currently all I have wired is the Booster to Main output XLR connections.

It’s shorting with and without DOAs installed.

Thanks
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on October 18, 2017, 10:57:22 AM
The + and - sides of both the ACA and Booster outputs are shorting together, is this a bad sign?

It’s shorting with and without DOAs installed.
These output pads have no connection at all when the PCB is unloaded. What you are measuring is the DCR of the output transformers that you have installed. It is likely not a direct short but a very low resistance. This is normal and expected.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on October 18, 2017, 08:30:49 PM
Hey Jeff,
Thanks for the reply.
To be more specific I was using a continuity (Buzz) test on my DMM and getting straight continuity between the + and - pads for each output (though not say between the main and mult outs).

My PCB is loaded, power is hooked up and reading as it should on the DOA sockets, the only off board wiring I put in before seeing this was the Booster our to 200b Main XLRs...
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on October 18, 2017, 09:05:19 PM
Hey Jeff,
Thanks for the reply.
To be more specific I was using a continuity (Buzz) test on my DMM and getting straight continuity between the + and - pads for each output (though not say between the main and mult outs).

My board is stuffed...
Yes I get that. The only component that will alter that reading will be the output transformers, nothing else. A continuity "beep" on a DMM usually sounds off well above 0Ω. If you want to check for sure, set your meter to read DCR and below 200Ω if its a manual range type.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on October 18, 2017, 10:09:05 PM
Ah ok, great. Thanks Jeff!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: grievousangel on October 19, 2017, 01:12:35 PM
Shouldn't the fader be 1K if using 48K isolation resistors and 2025 DOA? Working from memory so might be wrong.

Try this: Buy a cheap audio signal injector and inject audio tone from outside most circuit inward toward the DOA. When you lose signal or its severely degraded, the problem is mostly likely the section just in front of signal lost.

Billy
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on November 12, 2017, 08:32:04 PM
I have successfully installed this into my Soundcraft 200b.
All's working well and strewth it sounds incredible, such a step up from the 200bs master section.
It's got such clarity and heft to it!

On strange thing I have going on is that there are several points in the travel of my master faders where the signal jumps suddenly and then settles back quite quickly. Not unworkable in general but odd.

Any pointers as to what would be causing these sudden spikes?

Thanks.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: living sounds on November 14, 2017, 05:12:14 PM
I have successfully installed this into my Soundcraft 200b.
All's working well and strewth it sounds incredible, such a step up from the 200bs master section.
It's got such clarity and heft to it!

On strange thing I have going on is that there are several points in the travel of my master faders where the signal jumps suddenly and then settles back quite quickly. Not unworkable in general but odd.

Any pointers as to what would be causing these sudden spikes?

Thanks.

Must be incorrect wiring of the fader. What op amps are you using?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on November 14, 2017, 06:11:10 PM
Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: living sounds on November 14, 2017, 07:34:32 PM
Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).

I think I had the same problem. Measure the faders to make sure which lead ist the whiper. Intuition may be misleading.

Are these GAR1731? Which op amps did you put on the summing section and which on the buffer? I'm still experimenting with mine...
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on November 14, 2017, 09:50:32 PM
Would wiring the fader incorrectly cause that strange issue?
I'm using a couple of red dots and a couple of 1731s (that I built from a kit).
It could because this behavior is not at all normal.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on November 14, 2017, 11:29:24 PM
Re. Opamps I can't remember which way around they are now, I've swapped the positions once or twice and have a bunch of others I'll perhaps swap in and out... Yes they are the GAR1731 kits, pretty sure I've now ordered several of all of the available DOA's from CAPI to try out.

I'll investigate the fader wiring, I'd kind've thought if it was wired incorrectly it'd be a Working or Not Working deal. Not so much this strange issue.
I did get a bit of guidance from this thread: https://groupdiy.com/index.php?topic=54847.0
The OP in that mentions a similar issue though no resolution is offered.
All this being said it's not an unworkable situation, just a few VERY narrow spikes to pass over before settling into a usable level for mixing.
And again Jeff, killer project you've offered! Really improves things!
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on November 14, 2017, 11:38:47 PM
What fader is it and how do you have it wired?
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: lachlan.vercoe on November 15, 2017, 12:44:06 AM
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
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: jsteiger on November 15, 2017, 09:15:03 AM
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...
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: punk on August 27, 2018, 09:14:34 PM
installed, finally, into a soundworkshop SW34. very easy mod and sounds great.
thanks Jeff!!
byron
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: a_wachtmann on September 21, 2018, 02:50:38 PM
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
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: boji on January 24, 2019, 04:16:26 PM
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
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Math5461 on February 08, 2019, 06:58:30 PM
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



Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: Potato Cakes on March 26, 2019, 06:54:05 PM
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.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: MrBlomski on May 06, 2019, 03:36:15 PM
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.
Title: Re: [BUILD]CAPI 2-ACA-Bo~Official Support Thread
Post by: TubeMonkey on June 04, 2019, 02:36:33 PM
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.