Dennis,

I run the PSR-3000s left channel into the L1s channel 1 and the 3000s right channel into the L1s channel 2. This seems to produce a fuller sound, at least to my ears, when the two channels are combined within the L1. I believe much of this is due to Yamaha's pseudo mono output, which is not really a true combination of both audio output channels.

As I've stated many times in the past, the audience really doesn't know or care whether you are playing in mono or stereo--they just want to be entertained.

Good Luck,

Gary