Recently bought RA-03 amp and trying to connect to my existing avr3802 where the pre-out for main L/R from denon connects to one of the line input of RA-03, however, there's a very low audio coming out. Setup is DVD player to AVR then main L/R pre-out from avr to RA-03 amp. Main L/R speakers are in the amp.

Any advice? Do you have diagram on how to setup the AVR with the amp for both music listening and movie watching?