JBL SSA660 Integrated Amp, Why must it be switched to MONO

[Choatpadda]

for both channels in AUX input? I don't have the manual, any feedback would be greatly appreciated!

[BMWCCA]

Why must it be switched to MONO for both channels in AUX input? I don't have the manual, any feedback would be greatly appreciated!
You could search this site, but search using the correct model number: SA660.

You'd find such tidbits as a copy of the service manual for download:
http://www.audioheritage.org/vbulletin/showthread.php?p=170903

I assume you've swapped leads from your source device?

Good luck. I enjoyed those amps when they were new.