Of coarse you can use the keyboard's onboard effects Just plug the mixer into the mic input on the keyboard. Turn down the volume knob on the back of the 1000 and make sure you don't overdrive the input. By the way just send the 1000 a mono signal from the mixer not a stereo signal the mic channel is mono.

Mel
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KORG PA1000, KORG PA900, 2 BOSE S1 PROS, 2 BOSE L1 COMPACTS, YAMAHA STAGEPAS 500, ROLAND VP7