I've been testing out a number of audio options, and with Max2Play and Volumio my brand new Amp 2 + RPI4 worked no problem.
But I tried going over to a pure Raspian install, following these instructions: https://www.hifiberry.com/docs/software/configuring-linux-3-18-x/. The Raspberry Pi sees the Amp 2, but I don't get any sound out of it. I'm running at 19v DC.
`aplay -l` looks good:
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dacplus], device 0: HiFiBerry DAC+ HiFi pcm512x-hifi-0 [HiFiBerry DAC+ HiFi pcm512x-hifi-0]
Subdevice #0: subdevice #0
My volume is at 100%. I put a voltage meter across the speaker wires, and I do see some very small variations in voltage when I play sound (and only when I play sound), which is why I was checking on volume. Very strange.