Originally posted by zuki:
I don't understand what SUM means. Please explain how I'd hook the 800 into one Bose.
"SUM" the signal to mono simply means connecting both L and R outputs together into one mono input.
This can be accomplished with use of a simple Y cable adaptor if your keyboard does not have a MONO output, which most do. Use of the Mono output is the same thing exactly, it adds the two signals mathematically into one, yielding the SUM of the two signals, amplitude-wise.
--Mac