LMI DIY DI BOX PCB. This project uses an LMI 50600BRN transformer, which is modeled after the vintage transformers used in the classic Motor City and West Coast direct boxes. This DI box has massive character and “tone for days.”

Features a built-in special ground scheme as used in the Motor City Big Block DI, with the option to add a ground lift switch that shorts XLR pin 1 directly to ground, using the G and P1 pads.

This DI will work well with guitar, bass, keyboards and drum machines. The transformer is strapped for 12..5k to 600 ohms.

All components are labeled ((1) .1uF 50V ceramic capacitor and (1) 51 ohm ¼ watt resistor. Both the TS input and the XLR output solder pads are oversized and easy to solder wires to. Any enclosure that’s at least 2 inches tall, 3 inches wide and 5 inches long should work. There are plenty of options on Amazon that can work for this application. 2 mounting holes (M3, will also fit #4-40 screws) are provided for mounting to a chassis.

This pcb is designed to allow you the freedom to use your own choice of XLR and TS connectors. You select your XLR and TRS connector style, then wire your connections, attach them to the chassis and then solder to the respective pins on the PCB.

To complete your project, you will need to obtain an LMI 50600BRN transformer.

Please purchase the LMI50600BRN here on the LMI Reverb Account. https://reverb.com/item/55811395-lmi-lmi50600-2025

BOM here: https://docs.google.com/spreadsheets/d/14vAdzhV3EEVIOffHBeNZ8IWbqsLcJyjiV8buVmBmESw/edit?usp=sharing