I use minijack - rca/phono lead from the headphone socket to the amp. It has got the advantage of letting me use the remote for volume adjustment. To ensure the right impedance for the headphone output, I have soldered two 150 ohms resistors on the input socket on the amp.
I`ve got four cheap dacs from ebay, in different versions (just to try out). No problems, except for one wall-wart that broke down. I like the sound of the old multibit-dacs.

