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

[beezer4]

Hi all,
Wanted to share an update on the MCI JH-618 upgrade. Installed everything yesterday and it's working great! Leveraging a pair of Sphere/Quad Eight transformers for the booster amp, Quad Eight AM10 style opamps and adjusted for 10K summing resistors. Wired it as I had laid out in an earlier post with the schematic. Thanks @Brian Roth for the input! It made a fairly substantial difference in the sound of the master buss, super happy with it. I was able to find space in an empty slot and mount the board next the patch bay. Luckily, didn't have to cut any traces on the master module (just remove some components/opamps) and was able to easily run cabling to and from the new PCB. I was able to find the cable runs for the master sends on the patch bay, bring those directly to the CAPI board and balance them. Noise floor is actually lower than before.

One last item is figuring out the mute piece with the voltage drop vs presence.

I'll also be updating our blog as I continue working on the console: https://downbeatstudio.com/2024/05/28/upgrading-our-mci-jh-618-console-part-1/

Thanks all the for help!

 

[Brian Roth]

@beezer4 Cool! I was going to figure out a simple way to trigger that FET but I've been in and out of town so not near my 600 manual. Did you just "ground" the FET gate to keep it in the on mode?

Bri

 

[beezer4]

@beezer4 Cool! I was going to figure out a simple way to trigger that FET but I've been in and out of town so not near my 600 manual. Did you just "ground" the FET gate to keep it in the on mode?

Bri

Yep for now it is just grounded to keep it in on mode.

 

[Brian Roth]

Yep for now it is just grounded to keep it in on mode.

Yep, makes sense. MCI uses "0 Volt-ish" to mute. We need to add a inverter.

Bri

 

[Sukane]

Hello. I have aca booster board that i would like to use as output of a gssl compressor. I have connected output of vca to input of a aca booster and it works but i get unwanted distortion at high levels. Should i use buss resistor or opamp between gssl’s vca and aca booster? In pics i have drawn red circles around points that i have connected between gssl and aca.

Link to gssl schematic

 

[skidmorebay]

Question about using JLS-INV>2ACA BO as a summing amp to approximate an API console:
I have a 32 in/2 out summing amp, configured just like Jeff's block diagram:

The first stage ACA's feed a pair of 2623 transformers. The second stage feeds a pair of 2503's, followed by Bourns 600R attenuators.

My question is about calibration. If I send a +4dbu tone through this it comes back a lot louder, due to the 2:1 transformers. In a real API console, would the correct calibration approach be to send a +4 tone and adjust the fader between the two stages for a +4 return from the final output (attenuators wide open in that case)?
Or, would it typically be to get +4 output from the first stage, then reduce the attenuators on the output for a +4 return from the output? (That means hitting the 2623's a lot harder.)

Any API console users care to comment on which approach is traditional?
thanks!
JS