Flash Trigger Multiplier V1
I built a small flash trigger multiplier (1 in 4 out) on a small perf board. This has the same electrical connections as the Y Connectors and has the addition of a test fire button which comes in handy. Since the circuit is basically the same as for the Y Connectors the same cautions should be noted. This joins all the flashes together and should only be used when the flash guns are all the same make and model (or have the same trigger voltage).
Flash Trigger Multiplier V1 PCB
I later extended the flash trigger multiplier to have 6 outputs and created a PCB in KiCAD.
KICAD 5 PCB files for a 6 port trigger multiplier are available here. (4MB zip file).
Works with 1 to 6 flash guns.
Parts List
PJ-307 3.5mm stereo socket x 7
12mm momentary push button switch x 1