Since 2 weeks I hear music over a PI2B and a Hifiberry DAC+ with Volumio as Software. The most seems to be fine, the sound is quite good. But compared to my CD-player and the HDMI-sources it has much fewer deep bass then them. So I build a little line driver with an OPA 2134. Gain is 1. Now the bass is as expected.
Is it possible that the DAC+ can't drive the input impedance of 10k from my Amplifier? The cables are from Sommer and short as possible. The Amp is an old (but well working) Myryad MI-120. Even my cheap HDMI-Dac from China has no problem to serve the Amp.