Roel,
the main problem with the SD1 is the noisy DSP; the noise is evident in the "cyclic" effects, like chorus, flanger, rotary, etc.
When Ketron will have fixed this problem the SD1 will be a keyboard worth buying; until then, like I wrote some time ago, you have to consider the possibility of routing the SD1 outputs to an external DSP.
With sympathy and friendship,
Andrea
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.