I have bought the excellent Pi-DAC+ to use it with Volumio in an old radio I have. In this radio, the speakers are marked as 6 ohms impedance. This radio used to provide a rather good sound. But with my Raspberry 3 and Pi-DAC+, I only get a minimal volume (around 40dB of sound). So, is there some software configuration in Volumio to boost the sound ? Or should I use a bigger sound card amplifier ?