Most of the big manufactures have phone apps that multicast and allow control from a phone. Most allow you to play off USB. The big problem is that these manufacturers all have their own proprietary multicast systems (IMO an attempt to tie you into their system). These systems don’t play nice with each other.
The saving grace is that all of them support airplay … but that just allows you to multicast to these AVRs/prepro from iTunes server or device. You still need the manufacturers app to control each unit.
But you knew that … right
