Popping sounds when playing mp3 or flac

Pretty much anything I play through my DAC is popping and driving me nuts… The same DAC on a raspberry pi 2 is OK and the raspberry pi (b+) that has the problems works fine through HDMI, but the combination of the raspberry pi B+ and HiFiBerry DAC+ causes lots of popping when playing audio through volumio 1.55

Any suggetions to try and resolve this as I don’t feel the HDMI produces as good a sound and I only borrowed the pi 2, have to give it back… :laughing:

This is the exact DAC I have - geekroo.com.au/products/1482