2+ source priority mixer

Thread Starter


Joined Oct 8, 2019
Hello all!

The Preamble:
I'm new here, so this is my first post. Incidentally, I'm really excited that there is a community alive in well around these subjects. I'm a software engineer, so don't be afraid to speak technically to me, but I'm also certainly not an electrical engineer, let alone know much about analog/digital signals.

I read the "Please Read" at the top of this forum, but I'm in a little bit of a grey area. I found a topic that came pretty close to my project/needs, however, it abruptly ends around 2010 with no further development. I'm more than happy to revive that thread and post my question there, but I'm not certain that's the best move. Let me know!

I'd like to make my title very succinct and accurate, so (hopefully) I can update it as we go, and I learn more appropriate lexicon.​

The Project:
The goal of my project/idea feels simple to me: I'd like to build a circuit that can take two audio inputs, and fade the first one when a signal is detected on the second.

To put in more specific terms, I'd like to build a device that will pass through my car (aftermarket) stereo audio to the car speakers, however when signal from another source (CB transmission in this case) is detected, it reduces the volume of the stereo audio (ideally adjustable via a knob, but this can be optional for now) and passes through the CB (voice) audio.

Essentially building a priority switcher, but I'd like to be a little less drastic than just shutting off the audio entirely from the stereo, and rather "blend" the two sources, with the stereo at some fraction of its original volume.

Bonus points/stretch goal would be to shutoff/reduce the speaker audio volume (source #1) when the "push-to-talk" is triggered for transmitting over the CB.

I'm sure I should be using a more technical term than "volume", but I don't know enough yet at this point to even pretend like I know what I'm talking about. Happy to learn as I go and I will modify my language accordingly!

So ultimately, I'd love some help/guidance on how to design this circuit, and what would be needed. I think it would be pretty cool to have a compact set of plans that folks could use to build this project as I believe a lot of folks would find it useful. What are the next steps? Let me know if I can provide any more clarity or information around the idea/project.

As you can imagine, my limited exposure to this world leaves me without the right words to zero in on solutions that may already exist. I'll post some of the references I have dug up in a show of good faith that I've tried looking and I'm not asking someone to just hand me the solution on a silver platter (however there's a cold beer/drink of choice if you do! haha)



~ Dale

P.S. I work for an IoT company and ran the idea by a few of our hardware engineers, and they think it's quite doable, but I didn't have a chance to bend their ear so far as to help me design something. (yet?)