hmm. I've never used the expression pedal with it. I use one on my moogerfooger lowpass filter. I know that 10, 11 IIRC, don't allow the hold feature. Perhaps the expession pedal is tied to the hold feature. That might explain why it's not working too. Still, I can't imagine that being the case. It would be kind of awkward having to hold the pedal with one foot and use the expression with the other. Still worth eliminating the possibility for the piece of mind. Another thing you could check is the little polarity switch on the expression pedal. Mine can flip flop the sounds made on the up and down position. (if that made any sense to you

). I heard that not all pedals that take expression pedals like that. The SYB-5 has a significant learning curve. Just have systematic approach to your troubleshooting and I'm sure you'll figure it out.