Hi!
I'm working on a simple 2 channel stereo mixer product that needs to mix USB audio with either SPDIF or a TRRS connection. The idea is to play audio back to one headset from two sources, while still sending microphone capture back to both playback devices (effectively connecting a headset to two devices at once).
My current plan is to use two separate USB and SPDIF codecs that both produce analog outputs, and then use a simple op-amp based analog mixer (with volume and tone adjustment potentiometers of course) to mix the two stereo pairs. Finally, I'd pass the mixed audio signals through an op-amp based headphone amplifier to the headset.
I would also like to optionally accept a standard TRRS connection instead of SPDIF. I figured I would just add a switch to bypass the SPDIF codec to accommodate this.
Take a look at the attached "simple_topology" image for the basic idea.
So far I was thinking I’d use the PCM2912A for the USB codec, and one of your headphone DACs that accepts SPDIF input.
But here’s my first question: is there a way I can simplify this topology? Am I overlooking any of your products that can mix USB input with SPDIF input? It seems like mayyyybbe the PCM5906C can do this (but I think not)?
I’m also a bit concerned about the audio quality of a simple analog mixer at the end, which brings me to my second question: Do you have any simple digital mixing solutions? Perhaps I could use USB/SPDIF to I2S codecs and then a digital I2S mixer before converting the final output to an analog signal. I’m still looking for a relatively simple plug and play solution, but I could add a microcontroller to issue basic I2C configuration and tone/volume control commands if needed.
Thanks!
-Peter
