Help me Choose Between A and B

[card9inal]

Hey there guys and gals,

I'm working on an IFB project that will feed headphone amps. Normally, the headphones get a straight program feed, when the talkback button is pressed, the feed is now a dimmed program feed mixed with the output of a mic preamp for communication.

I'd like to be able to switch between two (or more) different program mixes in case someone needs to hear a different feed. So I've come up with a solution that I KNOW will work, and one that I'd like to use, but not sure if it's the right way to do things. Before I spend time breadboarding the circuit (and I can't because I'm on the road right now and can't get to my workbench!), could you guys give me any opinions on whether the B drawing will work, or do I have to stick with the A drawing?

This drawing only shows 1 channel, but there are several in the box, which is why I'd like to use the B circuit, to save space and components.

(EDIT: The A drawing is the first one with more components. The B is the simpler one.)

Thanks!!!

 

[Frank Berry]

"B" looks good to me. "A" seems to be overly complex. Before retirement, I designed an IFB system for a TV station. My design was similar to your "B" design. My inputs were LINE, AIR and TALKBACK.

 

[card9inal]

Thanks Frank.

I thought that it should be fine, but I just wanted to run it by some people who had some more experience in this world than I! I'm just getting started in designing systems (and component level electronics in general!)