I have an issue with my Yamaha RX-V567 amp. When powering the unit on from standby the audio will not output for 30 seconds to a few minutes, the unit appears fine otherwise and displays correctly. It doesn't matter which source; analouge/digital/tuner. After a random period of time audio cuts in as if it had only been on mute.

Has anybody come across a similar issue with this or another amplifier and what was solution?