Originally posted by travlin'easy:
If I recall, the last hot out of the box arranger keyboard made by Yamaha was the PSR-2000. The PSR-3000 was a bit subdued in comparison. When questioned about this on another forum, someone stated that most of the tweaking and tuning of the overall keyboard or synth sound was usually done with a stand-alone, powered mixer--not in the keyboard. However, because Yamaha also had a relatively large contingent of home users that did not use external amps they improved their onboard effects system and expanded its capabilities beginning with the PSR-2000. It has improved dramatically with nearly every ensuing model over the past decade. Made perfectly good sense to me.
Gary 
Correct Gary...and also there are several presets in the MIXER/EQ section to allow for various setups, and to provide a good base to start tweaking, if you so desire.
Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.