SDD-320 Dimension D

Roland's SDD-320 Dimension D stereo chorus rack was an instant studio legend upon its arrival in 1979. A subtle spatial enhancer, the Dimension was the go-to sweetener for vocals and piano in the early 1980s, used extensively by Brian Eno (who else), the Talking Heads, Kate Bush, Peter Gabriel, etc. In many ways the 320 is a predecessor to Empirical Labs' Distressor, which is increasingly ubiquitous and likewise revered as an "AWESOME" switch for its elegant compression and gain routines.
FEATURES:
Only the Roland SDD-320 Dimension D and Boss DC-2 Dimension C pedals produce a chorus that is more spatial and lacks typical pitch modulation. It achieves this through the use of dual sync'd delay lines that are driven by a trapezoidal LFO - key to avoiding warble.

LFO shape has a very noticable effect on chorus tone because the shape defines how the pitch moduation will occur - will it always be changing, will it hold for a time, how is the slope of the waveform, etc. In using two lines with a trapezoidal LFO (and companders, etc), Roland achieved the (lovely) psychoacoustic effect that is the Dimension.

Other chorus units have varying degrees of pitch modulation. Base delay time defines the chorus "color," the depth of modulation, or time delta, defines the pitch modulation - the deeper the mod, the more warble - and the LFO shape contributes to the effect character. This is true of both analog and digital units.