Wiring the M4

Grand Central M4 Wiring

Get the cables from the panel mounted components ready to wire into the Grand Central M4 Express. 2x toggle switches, 2x potentiometers, 8-way rotary switch and the perma-proto pcb. Use the following hardware.

  • 8x M3 x 6mm screws
  • 4x M3 x 20mm standoffs

Install M3 Standoffs

Place an M3 screw through the mounting holes in each corner of the Grand Central M4 PCB. Insert and fasten the M3 standoffs onto the threads of the screws. Finger tighten all four standoffs.

Label JST Cables

Take a moment to label the JST cables. This will help connect components together once it's been installed into the body of the guitar. I used the following letters to reference these components.

  • X – LIS3DH
  • A,B,C – MX Switches
  • P1, P2 – Potentiometers
  • W – Potentiometer for Whammy 
  • 1-4, 5-8 – Rotary Switch
  • S1, S2 – Toggle Switches

Wire Prema-Proto

Solder the perma-proto PCB to the ground and 3V pin on the Grand Central M4. Reference photo for best wire placement.

Wire Potentiometers

Solder the white wires from the 2x potentiometers to pin 2 and 3 on the Grand Central M4.

 

Pots Ground and Voltage

Solder the voltage (red) and ground (black) wires to the pins on the perma-proto PCB.

Wire 8-Way Rotary Switch

Solder the eight wires from the rotary switch to the following pins on the Grand Central M4.

  • 24-31

Wire 8-Way Rotary Switch to Ground

Solder the 2-pin JST cable to the ground pins on the perma-proto.

Wire the LIS3DH

Solder the green wire to SCL on Grand Central M4. Solder the white wire to SDA on the Grand Central M4.

Wire LIS3DH Ground and Voltage

Solder the ground and voltage wires to the ground and voltage pins on the perma-proto.

Wire Micro Switches (Strum)

Solder the 2-pin JST cables from the two micro switches to the following pins on the Grand Central M4.

  • Pin 22
  • Pin 23

Wire MX Switches

Solder the 3x 4-pin JST cables from the MX switches to the following pins on the Grand Central M4.

  • 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 14

M4 Wiring Mounted Components

Get the bottom half of the guitar body ready. The panel mounted components will be wired to the Grand Central M4.

M4 Wire Whammy Pot

Solder the white wire from whammy potentiometer to Pin #1 on the Grand Central M4.

Wire Whammy Ground and Voltage

Solder the ground and voltage wires from the whammy potentiometer to the ground and voltage pins on the perma-proto.

Wire Toggle Switches

Solder the 2-pin JST cables from the 2x toggle switches to the following pins on the Grand Central M4.

  • Switch 1 – Pin #52
  • Switch 2 – Pin #53

Wire Toggle Switches Ground and Voltage

Solder the voltage and ground wires from the toggle switches to the voltage and ground pins on the perma-proto.

M4 Wiring Check Point

Take a moment to thoroughly inspect the wiring.

Unplug Components

Begin to disconnect the various JST connectors. The components will need to be unplugged in order to install the Grand Central M4 into the body of the guitar.

This guide was first published on Mar 18, 2020. It was last updated on Mar 18, 2020.
This page (Wiring the M4) was last updated on May 25, 2020.