Hi all,
Just my 2 cents: I had the exact same issue, that is when installing RA version 0.4b on a Pi3, which is much better and stabler in every respect than 0.3, PLUS accepts the fantastic which 0.3 does not,
the max sound output was very low, either on the integrated soundcard or on a Hifiberry Dac+.
Going to the Alsamixer (
http://<your Pi IP>:8080), choosing the "sndrpihifiberry" card and setting all sliders to 100% fixed this. What did it for me are the "Digital Playback" sliders, that were at 47%. Note that these levels are independent from the RA/Dac+ software or hardware volumes.
RP