I would think that to have a 20 band eq, you'd only be able to have a mono output...
I'm guessing this from the current setup :-
4 channels of 5 band eq for front and rear stereo output
2 channels of 10 band eq for stereo output

Jazz
(List 112, Mk2 12 gig #40. Mk1 4 gig #30. Mk3 1.6 16v)
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Jazz (List 112, Mk2 42 gig #40. Mk1 4 gig #30. Mk3 1.6 16v)