: Ensure the correct digital input (Optical or Coaxial) is assigned to your source. If the channel indicators on the display flash, it means the digital signal has been interrupted. Harman/Kardon AVR-51 - Classic Audio
Download the PDF and save it to your phone. When you are behind the receiver with a flashlight, searching “digital input assign” on your phone is faster than flipping paper. harman kardon avr 51 user manual 134 better
Press button – disables bass/treble, shortens signal path. Good for critical CD listening. : Ensure the correct digital input (Optical or