TTSH Mod Sync Option
from Muffwiggler thanks to all supporters specially "Altitude" and "sduck"
pcb order from Oshaprk: https://oshpark.com/shared_projects/q9qiqYIa
i prefer Sync: for syncing VCO 3 to VCO2 and VCO1 jumper (set a bridge) JP2, V1 = out from VCO3(61k9 resistor), S1 to VCO1 sync input, S2 to VCO2 sync input (at input = 1k5 resistor)
its very important needed to use shielded cable for VCO I/O connections to the sub vco boards (dont forget to ground the shield)
for wiring to switches dont drill the cables, otherwise you get softsync issues.
Thanks to Steve (sduck) for sharing this helpful picture: