Ring Modulator
Last Edited: Dec 23, 2023
Analog Telephony
The ring modulator's original application was in analog telephony, where it was used for frequency-division multiplexing to carry over telephone cables. Frank A. Cowan invented it back in 1934 and in 1935 to improve the invention of Clydl Labs. IKeith's design has since been applied. Since then, it has been used in voice inverters, ions, radio transceivers, and as an effect in electronic music effects Ring Modulators.
A ring modulator is quite an old effect. However, it was not until diodes were used in the circuitry that ring modulators were found to be helpful in sound synthesis. One of the first synthesizers to use the ring modulator effect was the Melo-chord, built-in 1947 by Harald Bode. Due to the success of Bode's ring modulator, he went on to design a designated, stand-alone ring modulation. The Bode's ring modulator was a later built-in module format for inclusion in Moog modular systems. Buchla, Oberheim, EMS, and Yamaha followed and began including ring modulators in their synthesizers. Today, you can find a ring modulator in virtually any synthesizer. Ring modulators have become a synthesis staple. For that reason, they are abundant in numerous synthesizers, both analog and digital based.
Metalic Sound
The ring modulator effect sounds ear-opening, metallic, or robotic. The overtones produced by the ring modulator tend to be inharmonic. Furthermore, the effect can help sound "out" or play with music with no prominent tone center. In a ring modulator, the multiplication of a carrier signal and an input signal (guitar, for example) occurs. Consequently, the effect's character depends on the carrier signal's frequency. If the frequency is very low (below the range of human hearing), you will hear a tremolo effect instead of overtones.
Mixing Waveforms
Ring modulators frequency mix or heterodyne two waveforms and output the sum and difference of the frequencies present in each waveform. This process of ring modulation produces a signal rich in partials. Additionally, neither the carrier nor the incoming signal is prominent in the outputs, and ideally, not at all. Two oscillators, whose frequencies were harmonically related and ring-modulated against each other, produce sounds that still adhere to the harmonic partials of the notes but contain a very different spectral makeup.
Inharmonious Sounds
When the oscillators' frequencies are not harmonically related, ring modulation creates inharmonics. This produces bell-like or otherwise metallic sounds. The ring modulator includes an input stage, a ring of four diodes excited by a carrier signal, and an output stage. The input and output stages typically include transformers with center taps towards the diode ring. It is important to note that while the diode ring is similar to a bridge rectifier, the diodes in a ring modulator all point in the same clockwise or counterclockwise direction.
Bidirectional Flow
The ring modulator's particular elegance is that it is bidirectional. The signal flow can be reversed, allowing the same circuit with the same carrier to be used either as a modulator or demodulator, for example, in low-cost radio transceivers.
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