A builder here in the Phoenix area offered the OnQ A-Bus system is thousands of homes about 10-12 years ago. They are now all dying, with no replacement parts. Most of my clients have opted to replace the various technologies in that system - cameras, doorbells, etc - with new technology rather than a new A-Bus system.

I have retrofitted many homes with Ring doorbells, replacement camera systems or wireless Eufy cameras, etc. and am now replacing the distributed audio with small digital amps in the OnQ box. Arylic makes a wonderful, inexpensive amp that can be managed with their terrific app. I pull out the OnQ guts, build a mounting board to fit the box, put on as many amps as they have zones, install an ethernet switch to connect the amps to the Wifi system in the house (more reliable that way) then build a quick adapter for inside the box and behind the wall controller (replacing the control with a blank faceplate), essentially converting the Cat-5 into speaker cables. I measured an increase in resistance of about 0.4 to 0.6 ohms depending on the length of the Cat-5 run.

While I would not recommend this for folks who want rave-level volume from their in-ceiling speakers, this setup works beautifully for low to moderate listening levels that most of my clients want. In a few cases I have run new speaker cable from the wall plate to the OnQ box because it was quick and easy enough, but it is very cost effective and adequate to simply make adapters and hook up an appropriate amp. It also leaves the original wiring intact in case someone wants to convert back to A-Bus.