Great little project with an amazing sound!
For 808 Kick Drum Clone PCB
This is a great and easy little project with amazing sound! Also there is loads of room to experiment (changing the decay resistor for longer decay times etc.).
As the previous comments said, either connect the trigger tip to accent jack switch via 1N4148 diode (black band on the diode towards the accent) or connect +12V to the accent permanently. The sound is a bit different in either case so try both and pick the one you like.