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Ring Modulator By Paul White
Published September 1998


If you're after sonic strangeness, ring modulation is a good place to start. Paul White finds out whether the ColOSCIL sounds as big as its name.

Ring modulators have long been an essential ingredient in electronic sound design and advanced analogue synthesis — you only need to listen to some of the more creative dance records or sample CDs to see that it still rates pretty highly on the weirdness stakes. However, they're not often found in stand‑alone form; DACS apparently made their versions because a reggae musician asked them for something that would "f*@k with the sound". The result was the FwS series of ring modulators, of which the ColOSCIL 2 is the first in production.


Housed in a 1U rackmounting case, and with front and rear panels that look like a stomach's‑eye view of an hour‑old pizza, the ColOSCIL 2 comprises two independent ring modulators, each with a main input, a modulator input and a mono output, all on unbalanced jacks. (See the 'Ringing The Changes' box if you're not familiar with how ring modulation works) There's a single oscillator with a five‑position switchable frequency range, plus both tune and fine‑tune controls, and the main input passes though an equaliser (controls labelled Weight and Edge) before it hits the modulator circuit. The oscillator has a range of from around 0.2Hz to 16kHz, and it can be routed to the modulation input of either or both ring modulators by means of buttons on the front panel. These have status LEDs, as does the EQ, and there's also a power LED, but no power switch. When the EQ is switched on, the Edge control produces brighter harmonics, while Weight produces a warmer, deeper sound.

There are no input gain controls, no meters, and no clip LEDs — all signal level control must be done at source, and as the manual recommends input levels of between +4dBu and +12dBu to get a sensible output level, you'll probably need to use the device in conjunction with a mixer or other suitable preamp. Taking the input from a conventional keyboard's output jack results in virtually no output at all — you have to remember that this is a multiplier type of circuit so both signals need to be fairly large to give a sensible output.

Modulate What?

So what can you get out of it? The answer depends on what you feed into it, and the manual provides several useful suggestions. Feeding a sustained keyboard sound into the main input and a drum loop into the modulator input produces the kind of weird, grungy sound you get on a number of 'industrial' dance music sample CDs, and the nonharmonic elements often make the sounds seem distorted in unusual ways. Feeding the two outputs of a stereo keyboard into the two inputs produces something more like the old analogue synth ring‑modulation sounds, and is particularly effective for turning limp bass sounds into FM basses from hell! Using the supplied oscillator as the modulator can produce strange bell‑like tones at higher frequencies, whereas at lower frequencies it creates an unusual modulation effect that adds both chorus and strange harmonics at the same time. Most of the time, harmonically simple inputs produce the most musical outputs, with complex sounds or chords resulting in audio chaos. Often you'll hit on two inputs that produce something quite stunning, but you must experiment to give serendipity time to do its s tuff. The result is rarely musical in the conventional sense, unless you're feeding the same pitch into both inputs, and even then you may find one note sounds great while another sounds awful. This is definitely a tool for creating one‑off sounds that you can sample for later use.

Lord Of The Rings?

This is a particularly good ring modulator with no audible breakthrough when either input is removed, but I found the lack of input metering rather awkward, especially as the unit is pretty critical about levels. Similarly, the requirement for signals of up to +12dB cries out for a variable gain input control. Those comments aside, this device worked perfectly and enabled me to create an endless succession of fascinatingly weird sounds from the most innocuous of input sources. I feel it's a little on the pricey side considering its lack of facilities (though it isn't cheap to build), but its technical quality should endear it to serious sound designers, dance composers and anyone engaged in creating sounds for sample CD libraries.

Ringing The Changes

A ring modulator processes two inputs such that the output comprises the sum and difference frequencies of the inputs, but with the fundamental pitches of the inputs removed. This requires a balanced modulator circuit that in the old days was based around a couple of centre‑tapped transformers and a ring of four diodes — hence the term 'ring' modulator. In up‑to‑date designs the process is more likely to be undertaken with four 'quadrant multiplier' chips. The important things to know are that the output is only present when both inputs are present, the sum and difference output frequencies will most likely be nonharmonically related to the input, and the original signals will not form a part of the output. Modulating a voice or instrument with a simple oscillator produces anything from robotic voices to atonal, bell‑like timbres, while putting the same pitch into both inputs provides a harmonically changed sound that's one octave higher than the original.


  • Excellent technical performance.
  • Easy to use.
  • An endless source of weird sounds.
  • Two independent channels for creating two different weird sounds at the same time!


  • No input level metering.
  • No input gain controls.


A basic but high‑quality pair of ring modulators suitable for serious sound design and electronic music experimentation.