Chorus is one of the most essential effects for synthesizers and the chorus unit on many classic poly synths created much of their sonic signatures. This card for the Tiptop Audio zDSP Voltage Controlled Signal Processor offers 8 different algorithms inspired by some of the most classic effects in the genre.
Chorus effects use one or more delay lines which are modulated to produce a ‘doubling’ of the sound as if more voices are present. Programs vary from two to six delay line ‘taps’ or voices. Generally, the more voices the thicker and more complex the sound.
The delay times of these programs tend to be in the 18-24 millisecond range which is com- mon to most of the high end studio devices. Analog pedals are more in the flanger < 10ms range in order to use cheaper BBD parts, but there is also a Dual Flanger program with shorter times on the card.
LFO modulation provides a way to not only break up the comb filtering of a static delay, but also creates a sense of movement in stereo. Several of the programs use one or more methods like multiple LFOs, quadrature LFO, random walk and phasing to produce even more movement in the stereo field.
LFOs have both Rate and Depth controls: Rate is simply the speed of the LFO, and depth is how wide the LFO sweeps through the delay line.
Adding external Feedback can make the Chorus sound more intense and high levels of fee- dback can add a small room ambience. The Dual Flanger program has an internal feedback for the classic Flanger swoosh.