I use the Z2300 as well with my keyboards / PC / TV

you can run it through a small mixer which will have EQ settings.
I use a behringer XENYX 1002 with my Korg PA 500 and Motif XF.

you can get much better results this way...

Nick
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Roland G70 / Roland BK9 / Roland GW8-L / Yamaha Motif XS / Technics KN6500