Zero Loss FX loop kit


The original and still the BEST!

Since Steve Miller discovered the LND150 FET in 2005 and  created the circuit that passes full preamp signal to/from external FX, with ZERO loss.  This has set the standard.


Newly updated Rev 4 adds integrated level switching to the exceptional Zero Loss loop. On board switch allows selection of pedal level or line level (-20db or +4bd) to accommodate anything from pedals to high end rack gear at the flip of a switch.

We officially support this loop when installed in Marshall 1959, 1987, 2203 and 2204 models, and authentic replicas of these amps. The installation instructions are specific to this style of amp, with the long tailed phase inverter circuit. The loop will also work great in many, many other tube amp circuits, but we do not supply specific instructions. Please download the instructions from the link below to determine if the loop is compatible with your amp. Also, any good tube amp tech/designer can tweak this loop to work in most applications. It has been used successfully in tube amps from 18 to 200 watts.

Loop dimensions are 3 3/8" x 1 3/4".

Included in DIY kit:

  • loop pc board - loaded and tested
  • mini toggle
  • 22g wire
  • shielded coax
  • shrink tubing
  • ground lug and screw
  • various power supply resistor values

Download the instructions here: Zero Loss Version 4.1

Link to more info on the Metropoulos forum: FX Loop thread


Facebook group dedicated to the loop:  Zero Loss group

Also available as an assembled and tested board only for OEMs and those who don't require the extra parts (switch, wire, ground lug etc). Contact us.