Adding a "B" buss to a CAPI-ACA summing amp
« on: October 23, 2019, 09:34:09 AM »
All,
I'm gathering my thoughts for a 24 into 2 API-style summing box, based around the CAPI 2-ACA-BO cards and some various parts I already have on hand. I would like to have a way to send some (but not all) of the inputs back out to a processor for parallel compression and then back in to blend with the main mix. It's a lot like a cue send output that returns to the mixer.

For each of the 24 input channels, the signal path would be:
DAC output>47k buss resistor>ACA input>ACA Output>Booster Input>Booster Output

Where would it would be best to mult the signals selected for the B buss? After the 47k buss resistor, or before?

All of the selected channels would need to be summed and sent out as a stereo feed to a compressor. (I've got a CAPI JLS-Inv board I could use to sum the selected channels.)

What about this?:
Select channels in pairs via 12 toggle switches>47k buss resistors>JLF-INV input> output to  THAT 1646 IC's (or even unbalanced), stereo compressor>back in through THAT 1200 IC's, > a 10k Elma Stereo rotary switch I already have, >47k buss resistor>ACA board?

Or maybe I should mult all of the signals to the B Buss, and just have a toggle switch in line to interrupt the signal for those channels I don't want to send there?

The CAPI SumBus project has a lot of these features, but I'm hoping to do this on the cheap with parts I already have. Anyone know how it works on the SumBus, or have a better idea of how to accomplish this?

thanks,
JS


Floti

Re: Adding a "B" buss to a CAPI-ACA summing amp
« Reply #1 on: November 06, 2019, 10:58:43 AM »
Under Mixers/Monitoring Systems I have a post where I explain how I´m modding my Toft Console into an API style console. There is in POST 1 a pdf file with the schematics for my input channels. Look on page 4. I think that should help. That´s how I send the channels to the groups or the Mix bus.

Rocinante

Re: Adding a "B" buss to a CAPI-ACA summing amp
« Reply #2 on: November 06, 2019, 01:40:17 PM »
Under Mixers/Monitoring Systems I have a post where I explain how I´m modding my Toft Console into an API style console. There is in POST 1 a pdf file with the schematics for my input channels. Look on page 4. I think that should help. That´s how I send the channels to the groups or the Mix bus.

I've been reading and going through your documents on this. It is awesome man.
If there's a harder way to do this, I haven't found it yet.

Re: Adding a "B" buss to a CAPI-ACA summing amp
« Reply #3 on: November 10, 2019, 06:48:39 PM »
I just got back to this and am absorbing your schematic now. Thanks a lot for posting it. I think it's going to be a big help.

Lately I've been contemplating doing a Neve style summing mixer instead basing it on the CAPI, using passive summing into 1272-style amps. Lots to figure out still.

Re: Adding a "B" buss to a CAPI-ACA summing amp
« Reply #4 on: December 01, 2019, 11:37:29 PM »
Floti,
Thanks for posting your schematic. I see how you are switching the different buses into the left and right outputs on page four of the Toft input schematic you mentioned.
What is the purpose of R82 and R83 (47k resistors to ground on the legs to the left and right bus)?
thanks,
JS


 

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