This pcb is for the LMI DIY Transformer box project. This board utilizes 2 LMI10 transformers, using a special internal balanced circuit that extends transformer bandwidth while offering gorgeous tone and character.

This board will work for a mono channel. You will need 2 boards and 4 transformers to make a stereo set.

This PCB also features an optional chassis ground connection and an optional T attenuator output level control. This attenuator allows you to drive the transformer harder while dropping the output level so that the next device won’t be clipped.

A great use for this design is with a set of converters where the user is looking for extra tone and vibe on their mixbuss or the output of a drum machine that needs some extra oomph.

There are only 6 total components per project, 2 LMI10 transformers, 2 resistors and 2 capacitors. The bill of materials (BOM) has links for all the necessary parts.

A standard 10K potentiometer that can be wired is all that is needed to attenuate the output level.

All solder pads for wires use larger hole diameters and pads for ease of soldering. Ground pours are on both sides of the PCB with large thermal reliefs for ease of soldering to ground pads.

2 M3/#4-40 holes are available for mounting. These pcbs are small enough to install into a small enclosure that is at least 4 x4 x 4. Allow some space for jacks and controls.

BOM: https://docs.google.com/spreadsheets/d/1M-N4P-SpkIswmtWpCIupFmdYMQl_-m3DdI2L2ANYfMg/edit?usp=sharing

Reverb link for LMI10 transformers: https://reverb.com/item/91690905-lmi-lmi10-1-1-transformer-2025-black

Thanks -L.