Most of the posts on ALSA mixer settings seem to be a couple of years old, so hoping to get some info.
I'm using DietPi Linux version 4.9.62-v7+ with Roon Bridge and the DAC+ Pro. When selecting the audio interface, I set defaults, so all volume controls are at 0dB (see amixer output below). What I've found is that when plugged into my amp, the DAC is quite a bit louder than my turntable. Since I cannot trim volumes for different amp inputs, I figure that I should adjust the DAC volume through ALSA mixer. I had thought that I would want to adjust the post-DAC analogue volume, but the Analogue dB Gain and Analogue Playback Boost parameters are either "on or off". The only gain control that is fine grained is the Digital dB Gain but I thought that adjusting this would essentially lose resolution. So my question it what should I adjust to trim volume but not impact sound quality?
Finally, should the DSP Program setting be adjusted from the default of "FIR interpolation with de-emphasis"?