Episode 20 – One Band Modular Vocoder

Vocoders are complex machines but working with a simple principle. They take two inputs and put them through filterbanks. After each filter of one filterbank are envelope followers that sort of detect the amplitude of that signal. This is called the analyze section of the vocoder. After each filter of the other filterbank are VCA’s that get controlled by the CV from the envelope followers. This is called the synthesize section. Thus the frequency spectrum of one signal is imparted on the other but only if that signal contains those frequencies. Usually vocoders sport filterbanks with at least 10 filters in each, expensive if you want to do it with a modular. Also, really good vocoders allow you to rerout the envelope followers CV’s to other VCA’s so that e.g. a high frequency filter in the analyze section controls a low frequency in the synthesize section.

This video is a demonstration of the principle of the vocoder but using just one bandpass filter. Since the filter is voltage controlled it opens up for a few extra benefits and it actually works pretty well as a vocoder.

Video link:

~ by 7thdansound on November 16, 2010.

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