Home Theater Questions? Ask a Technician for Answers ASAP
Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, is the 3.5 mm plug inserted all the way into the headphone jack?
Is the connections using a 3.5mm plug to twin RCA plugs similar to the product shown HERE? ...and plugged into any unused red & white input RCA jacks of the AVR-1604?
Still, perhaps you can try the Denon in AM or FM? ...or even consider a RESET?