Oakley Sound Classic Ring Modulator Module

"This is a vintage ring modulator design with bags of character. It is based on the classic ARP4014 sub-module which was used on the ARP2500 modular and ARP2600 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."

http://www.oakleysound.com/ringmod.htm