My problem is that I know enough to be dangerous, and not enough to do much practically. I keep fantasizing about going back and getting an EE degree or something, but after 15 years of taking university classes, I don't want to start that grind again.

I've built small arduino projects, such as PIR sensor controlled under-cabinet lighting and a foot-controlled "prev/next" buttons for a slideshow display, but I'm now lost in working with audio.

I'm wanting to build an audio mixer next, but audio is proving to be difficult for me to reason about. The rest of this post will talk about my idea, so skip it if you're not interested, or read it if you want to give me any ideas! :)

Here's the full idea (for which I have not been able to find a commercial alternative): I want my home automation (RPi and Home Assistant) to integrate with my house's current speaker system and be able to mix audio on demand. For example, if an audible alert needs to be played, then the volume of whatever is currently being played will be reduced so that the alert can be heard, and then restored when the alert is finished. So if I'm watching a movie and my garage door opens, I want to know about it! Additionally, music should be able to follow me from room to room, and I should be able to send audio to one specific room if I desire. Finally, my digital organ has multiple audio channel outputs in order to replicate the pipe placement in different parts of an auditorium, and I would like for this system to support that as well (make the far-away pipes play from the next room, for example).

In order to accomplish this, I want to build a zigbee-controlled audio mixer (with on-device fallback controls) for making use of my house's audio system (pre-wired when I bought the house, but the seller took the audio system with them and left the speakers!!) in conjunction with Home Assistant. Personally speaking, I don't like any solution that relies on a 3rd party to still be in business and be supporting my product a decade later, so self-hosted it is!

I assume that I need a lot of ADCs for the inputs (14 channels in... yes, I have a reason for that many... and 18 channels out). I would want the mixing to be "any input channel can go to any output channel", so using a CPU for the mixing would undoubtedly be better than trying to do it all with discrete components. The thought of building an 18-channel amp is a bit daunting! 7 stereo inputs (3 of which are really the 5.1 audio input) and 9 zones (3 of which are really a 5.1 speaker setup that is currently not being used at all) is a tall order for any commercial solution. Generic mixers do exist, of course, but they usually don't support that many outputs (and they definitely don't integrate with HA!).