Yes, you can still use the B1 with the original A5 model! With this kind of setup, you'd just need to use either an RCA to mini-stereo adapter (like the one that was included with your A5s) or an RCA to mini-stereo cable. You would just connect the RCA end into the RCA outputs of the B1 and the connect the mini-stereo side to either the top or back mini-stereo inputs of the A5s.