RM4014: Oakley Ring Modulator Module

Constructional difficulty: Small module with some simple setting up

The Oakley RM4014 Eurorack Ring Modulator module in a 8-hp faceplate.

This is a vintage ring modulator design with bags of character. It is based on the classic 4014 sub-module which was used on the 2500 modular and 2600 semi-modular synthesisers. The design has a fully discrete core but uses two op-amps for input and output amplification.

A ring modulator has two main inputs, usually called X and Y, and one output. The output voltage is the product of the two input voltages. In other words it multiplies the two input signals together to produce a new and different sounding output. If you have two sine wave input signals then the output will have both the sum and difference frequencies. For example, if X is a 440Hz sinewave and Y a 40Hz, you would get a 480Hz and a 400Hz sinewave from the output. However, this is only really true in a perfect ring modulator... And this ring modulator is not that. Each input has its own differing non-linearities or imperfections. This greatly adds to the character of the resultant output.

The Oakley Ring Modulator features three rotary control pots. Each input has its own attenuator, and there's also a offset control for the Y input. In conjunction with the Y attenuator, this third pot effectively acts as a wet-dry control for the X input. But because of the non-linearities inherent in the design it also acts in more subtle ways.

You can also use the Oakley Ring Mod as a standard VCA. Just use the Y input as your CV input and X will be shaped accordingly.

Each input can be either direct coupled (DC) or high pass filtered (AC). The former allows DC and low frequency signals to be processed. While the latter provides a DC block to process only alternating frequencies. The standard panel design makes both types of input available with each having its own socket. However, you can use a one socket on each and then use a switch to select between the two modes if you prefer.

This is a Euro sized module is designed to be run from +/-12V with the usual Euro 2x5 power header. The pots are Alpha/ALPS 16mm types with special matching brackets. The pot spacing on this module is 1.45" (37mm).

The current draw is approximately 35mA when run from +/-12V with no signal output.

The PCB is 86mm (deep) x 97mm (height).

As with all Oakley projects the PCB is double sided with through plated holes, has tough solder mask both sides, and has bold component legending for ease of construction.

The fully populated issue 3 ring modulator module behind a 8-hp Scheaffer panel.

Sound Samples

The following sample set was obtained using the ring modulator with an Oakley VC-LFO as the modulator (Y-input). The first of the three sounds uses a stable sine output from an Oakley VCO as carrier whilst the VC-LFO's frequency is manually swept with the frequency pot - this shows the huge range of the VC-LFO's frequency pot. The second sample processes the output of two mixed saw VCOs and sweeps the frequency of the VC-LFO from high to low. The final sample uses the same two saw VCOs but triggers the VC-LFO with the gate thus each new note always fades up from nothing.

This time we have an Oakley VCO sine which feeds the carrier (X-input) and a VC-LFO triangle wave as the modulator (Y-input). The X x Y out is going to an SVF filter whose low pass output goes to the master VCA. The SVF and VCA are controlled by an ADSR and the whole thing is sequenced from a P3 via a midiDAC.


Click here for how to order.

Ring Mod issue 3 (Euro) PCB .......................... 16GBP

Ring Mod pot bracket kit ................................. 0.75GBP

The Pot Bracket Kit contains three Alpha pot brackets.

All prices include VAT at UK rates. Shipping and postage is additional to these prices. See also the FAQ page.

Ready made modules are normally available from Krisp1.com.

Project Downloads

Builder's Guide

User Manual

Construction Guide Our handy guide to building Oakley DIY projects

Parts Guide Our handy guide to buying parts for Oakley DIY projects.

Schematics are available to purchasers of the PCBs and will only be sent via e-mail when the board(s) are shipped.

Front Panel database

A Schaeffer front panel can be made in either the 10HP or 8HP versions:

ringmod-10hp.fpd 10HP module in standard natural finish. The socket hole sizes are for Cliff 3.5mm sockets.

ringmod-8hp.fpd 8HP module in standard natural finish. The socket hole sizes are for Thonk PJ301 sockets.

To read, edit and print these files you will need a copy of 'Frontplatten Designer' from Schaeffer. Panels can be ordered via the program using its secure online ordering system.

Schaeffer are based in Berlin, Germany and can send panels to anywhere in the world. Delivery to the UK normally takes around ten days. For North American users you can also order your Schaeffer panels from Front Panel Express.

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Copyright: Tony Allgood.
Last revised: June 27, 2019.