Ring- and amplitude modulation

Author: Roland Kuit

Reworked by Wout Blommers

This Workshop has two parts:some basic explanation of Amplitude and Ring modulation and a practical part, without comment, but surely fun for analyzing sounds.

Feel free to skip the first part to go right away to the experimental Workshop. Be sure to check the Knobs.

Amplitude modulation and Ring modulation are both multiplicative ways to create musically interesting sounds in electronic music. Amplitude modulation is commonly done by a low frequency signal modulating an audio signal (tremolo). In scope of this workshop Amplitude modulation and Ring modulation are done with audio signals The difference between the two modulation types is Amplitude modulation contains the two original signals at the output, while using Ring modulation these are suppressed.

To understand the Amplitude/Ring modulator the term side band is very important. These side bands are found by the sum and the difference of both signal frequency values (Hz), e.g. a carrier signal of 200 Hz and a modulating signal of 300 Hz will result in two side bands of 100 Hz (M-C) and 500 Hz (C+M).

Amplitude modulation

 Ring modulation

Amplitude Modulation

A way to create the modulator in the Nord Modular is using the GainControl. This module multiplies two signals.

Opening this Patch both signals are heard, together with both side bands. Typical Amplitude modulation. Turning Knob 4 will make the carrier signal disappear, resulting in Ring modulation. Tweaking Knob 2 and 3 the changing side bands are clearly audible. Set in Ring modulation (Unipolar button 'none') turning the Modulator frequency up will result in a side band rising and in case of to a lower value as the carrier one side band will rise and the other will fall, which should be mathematical right. In case both inputs have the same frequency, only C+M will be at the output (C-M = 0).

Another way to use Amplitude modulation in the Nord Modular is done by the AM input on most Oscillators (Osc C, OscSlave A, OscSlave E and OscSineBank) and all Envelope Generators. And of course the RingModulator module, which has an Amplitude setting.

For which purpose can Amplitude modulation be used? It is an elegant way to create harmonics in a controllable manner. Take a look at the next example:

In situation A Carrier and Modulator are both 200 Hz and in the output will be C, M, C+M and C-M, which result in 200 Hz, 200 Hz, 400 Hz and 0 Hz. In reality the carrier and an octave. Situation B gives the next output: 200 Hz, 600 Hz, 800 Hz and 400 Hz, a harmonic range of a tone with its octave, a 5th and its double octave. Example C has an output of 200 Hz, 1000 Hz, 1200 Hz and 800 Hz. By using the Master/Slave setup (capable of precise settings of harmonics) and Amplitude modulation interesting sound can be created.

Using complex wave forms containing more harmonics will result in more frequency sums and differences, so more side bands appear.

The following Patch looks complicated, but the Amplitude modulation is done by a wave form, generated by the X-Fade/LFO connection and the Amplitude of the modulating signal can be changed by the two Constant modules.


Ring Modulation

 

 A side band of a third

Creating a perfect fifth

Ring Modulation and metallic sounds

Mostly Ring modulation is used for creating metallic and bell like sounds. In the early electronic studio's this delivered complex enharmonic textures, which could be filtered. 

Other effects created by Ring modulation

Echo by Ring modulation

It's important to notice if there's no signal on any input in Amplitude modulation or Ring modulation, there's no sound at all. In this Patch an Envelope Generator will silence the Modulation input on the RingMod Module. Every signal can be used to archive this, e.g. an extern audio signal.

 The echo

Complex timbre examples

Wrapped sine waves

 The Ring Modulators and filters

 Filtered Ring Modulator Feedback

Coloring Noise by a Ring Modulator

More control by the Ring Modulator

Colored echo with the Ring Modulator

Pitch control by Ring Modulation

 Ring Modulation controlling Timbre

 

 

 


Post Script

The Ring Modulator of the Modular looses small amounts of 'electro current'. Clavia reconstructed this strange behavior of the analogue module into the Virtual Analogue Nord Modular.

As shown above there couldn't be any signal at the output if one of the inputs isn't connected. Never the less a sine wave is noticeable. After connecting the VoltageProccessor to the Modulation input, the signal is silenced.