I'm using a Raspberry Pi 2 as an AirPlay receiver connected into an external amp via the headphone socket, and running
shairport-sync. I am seeing a low volume on the headphone output socket, such that I need to turn the input gain on the amp up far more than any other signal source, and have the RPi's output gain on 100% to be able to get a decent signal. I have eliminated
shairport-sync as they cause by just using
aplay and the various samples. So this this is a Pi issue.
Here are some observations:
When I change the output device between headphones, HDMI and auto using
amixer cset numid=3 N(where
2), the output volume does not alter. I am wondering if it's always coming out the HDMI port and I'm just hearing bleedthrough of the audio.
When I reduce the playback volume using
amixer, not only does the sound get quieter, but I also get distortion, exactly as set out in this (unanswered) question.
If left at 100%, apart from being quiet, the sound is of reasonable quality I suppose (I'm guessing it isn't a HiFi DAC).
All the shairport tutorials (which are mainly based on the RPi 1) seem to suggest the volume is too loud at 100% and should be turned down. Is this a common issue? Or is there some hardware-esque setting I can use to fiddle with the gain?