Passive Ring Modulator Assembly Instructions

The Synthrotek Passive Ring Modulator is one of our simplest circuits to build, but yields the biggest payoff.  It’s great for a beginner’s first project or the experimental musician. Retro sci-fi weirdness, crazy modulation, and unlimited sounds are possibile with this project.  One of the best features is that this circuit requires no battery power at all – everything is passive.

Parts Layout

Before you begin building your Passive Ring Modulator, make sure you have all the parts to complete your project.

Ring Modulator Kit

1x Ring Modulator PCB (Printed Circuit Board), 4x 1N34A germanium diodes, 3x mono audio jacks (1/8″ or 1/4″), 2x 42TM018 transformers, and wire; that’s it!

Let’s get started building!

PCB Components

Soldering diodes to the PC board

When soldering the diodes to the board line up the black (-) lines with the thick white lines on the PCB.


Before inserting the transformers into the board, bend out the side mounting pins so they will be flush with the board.

P side S side

Also, each transformer has a P (Primary) side and a S (Secondary) side. Make sure to match the sides up properly with the indications on the board

Transformers on board

Nice! Now for the wired components!

Wired Components

Choose your length of wire, strip it, then solder the wire to the tip (where the tip of your guitar cable would make contact) and sleeve (ground) of your jacks.

wiring, Synthrotek
Wiring to the board

When soldering the wire from the jacks to the board, make sure it goes in the correct place! T is for Tip and S is for Sleeve Complete Ring Modulator If you are using 1/8″ jacks with your Passive Ring Modulator,  here are some extra pics to help you hook it up right: 1/8″ Mono Jack The middle solder terminal is not used, so you can cut it off if you want. Complete Ring Modulator With 1/8″ Jacks

That’s it!  Now go and make some crazy music!




  1. Bill J. says:

    I’m sure that I’m not the first person to try this. I ran my stereo guitar rig through this circuit as the input and carrier. The result with 20dB gain on both, and Fuzz on the input only was a step towards an Electroharmonix Octavia. It’s still really gnarly sounding but definitely something for me to experiment with. 🙂
    Great little kit! Thank you!

  2. Jean-Sebastien Nicol says:

    Can it accept euro levels?
    How many hp’s if I mount it on a euro panel?


  3. Jean-Sebastien Nicol says:

    Would it be practical to have attenuaters on the input signal and on the carrier’s input?

    If so, 100k log pots?


  4. Jean-Sebastien Nicol says:

    Could it be mounted on a 1u 12hp?

  5. Steve Harmon says:

    Hey Jenz,
    It’s .85mm too big to fit in the 1u row :/ I suppose you could dremel down one side a bit, though!

  6. Steve Harmon says:

    That would definitely get you a bit more control of the experience! 100k log are what I’d give a whirl with to start. You can always fiddle about if the response is too little great for you 🙂

  7. Steve Harmon says:

    You bet it can handle them hot euro signals!
    The Ring Mod board is about .2mm bigger than a 6hp panel.

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