Talkback modification on console

[Travis1000]

Hey all, I have an old Audioarts 8X console. I just moved into a new space and one of my partners is very adamant about having a foot switch to engage talk back. This seems pretty easy. Just piggy back the foot switch over the switch I use for talk back (the studio button).

While I am in there I would also like to make the talk back dim rather than mute. As I have looked at the schematics, I am guessing (and it's a big guess), that I need to change the value of either the capacitor feeding back in to opamp Z, or the resistor feeding back into opamp AA.

Once I figure that out, I need to put the right value of passive component to dim the output of the console rather than mute.

I was hoping someone could point me in the direction of how to calculate that, and give insight into which amps are affecting that level.

Attached is the schematic. This is a link to a higher resolution PDF.https://www.dropbox.com/s/3blvewbt3pjblu7/RT%20Output%20Module%20pages%20merged.pdf?dl=0

As you can tell, my knowledge is limited but growing. Have I left any info out?

 

[zamproject]

Hi

You need a DPDT pedal switch, or a relay paralleling BOTH throw of "studio" switch.
One function is to send mic audio to studio out
Other is to light a LED and change logic state of mute FETs at CR buffer amp (O and J)
The mute is at those FET (1 and 3 from top), not at Z and AA
you can try a simple passive dim with two resistor or a pot  at  the FET S and D
BUT you will have another new problem, solo function will non longer cut audio coming from 2TK or stereo mix...

Best
Zam

 

[Travis1000]

Thanks zamproject! that is extremely helpful! Can anyone point me to the direction of calculating the correct resistor values?

 

[ruffrecords]

The mute seems to be operated by the solo logic, which makes sense because when sosoling a channel you do want to mute all the others. I cannot see where the TB switch gets involved in this.

Cheers

Ian

 

[zamproject]

The mute seems to be operated by the solo logic, which makes sense because when sosoling a channel you do want to mute all the others. I cannot see where the TB switch gets involved in this.

Cheers

Ian

hi Ian

link 35, also come from all TB signaling throw switches

Thanks zamproject! that is extremely helpful! Can anyone point me to the direction of calculating the correct resistor values?

You can try to just put one resistor paralleling drain to source of FET
the buffer have gain of 1 (10K/10K)
by putting 30K you have 12db att
FET passing --> 0ohm still g=10K/10K=1
FET cut --> 30K you have the g=10K/(10K+30K)=10/40=0.25=-12dB
for -20 dB you need g=0.1

--------

the solution to keep the solo function muting the mix return, it's to cut wire (or track) 35 between TB and solo sens (don't cut solo bus signaling), then cloning + paralleling everything around opamp Z, including 2 mute FET (not AA and solo FET). And then just reconnect your TB 35 to this new circuit.
You should have:
1- keep the solo sense driving 4 FET when soloing
2- the new circuit with 2 new FET(+resistor dim) just dim the mix and 2TK return when pressing any TB button

Best
Zam