I was having the same issue with my pi3 and noticed that when I rebooted without my ds4 controller plugged in, I had sound. I'm not sure if it is just a coincidence but it has already worked for me twice.
@Bradley-Cable I had the same problem, I was using berryboot to boot the system, I installed the direct recalbox on the SD and it worked, if you are using berryboot or another system for multi-boot, try installing directly on the sd card
@Antiheld 20 Mb/s isn't slow. The Pi can't handle more than that.
There has been a lot of discussions about SD cards... sometimes it is just a mistery... sometimes we just don't understand, others we make something wrong without being aware... who knows!