Hi @alexpikkert –
WRT your second observation, I suspect that the sequencer as some timing requirement on its gate signal. I can’t remember if I passed this suggestion to the littleBits folks, but it would be great if they published the timing requirements for the gate signal. This bit of info would eliminate a certain amount of trial and error. It would also help to publish a set of requirements and guidelines for using the Arduino buffered outputs (D5 and D9) with everyday digital circuits. The OP AMP slew rate affects timing when driving CMOS logic.
All the best – pj