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Ring-Modulation Demo

This simple demo implements a classic ring-mod effect, famously used for scaring small children in the 1970s with Dalek voices.

It also demonstrates how to build a simple GUI that sends custom events to the patch and uses them to trigger sample playback.

The samples included are taken from the BBC’s web-audio example

DSP Overview

Ring Modulator

A ring modulator multiplies two audio signals together, resulting in a sound that is a combination of the original signals. A simple ring modulator is achieved by multiplying the input signal with a carrier signal, such as a sine wave.

The ring modulators from the TV show Dr. Who also had a characteristic distortion. This is due to the diode blocks within the analogue ring modulators of the 1950s/60s. They result in hard clipping of the signals, creating the classic distortion.

Simplified Digital Model

For this demo, we use the simplified ring modulator research from a paper by Julian Parker.

This contains a block diagram and a branch equation we can use to model our example.

Block Diagram for the Ring Modulator

We use a sine wave as the modulating signal (Vin) and audioIn from the user (Vc). Two distinct diode blocks are created, each utilising a phase invert signal that is combined with the distorted signal. Both diode blocks are then summed back together to complete the ring modulation effect.

Click here to view the source code.