That's the objective of the Chorus/Delay: it can provide the classic doubling effect of a chorus, that simulates the presence of two guitars playing together, but as a delay, it can also give dynamics and depth by using very short echo sounds (within the 200ms range).
The Chorus/Delay was issued with the Sustainor 100, in January 1986. This second blue-face Rockmodule was produced until the last quarter of 1987, and was replaced by two units: the Rockman Stereo Chorus and the Rockman Stereo Echo. These new items didn't make the Chorus/delay obsolete - just different.
Inside the Module
The heart of the Chorus/Delay is the MN3005 BBD chip. A BBD is the basis component of all the analog chorus effects (25ms delays with an excellent Signal to Noise ratio). It can be pushed up to 200ms delays, at the price of a S/N degradation: 75dB only at the longest delay setting.
In order to improve this poor S/N ratio, SR&D has included in the Chorus/Delay a noise-reduction circuit, based on the same principle as the Dolby System: a "compandor".
A compandor is a dual circuit composed of 1) a compressor before the source of noise (the BBD in our case), 2) an expandor after the source of noise.
The expandor increases the level difference between the sound signal level and the noise level. The signal-to-noise ratio is highly improved, but the dynamics of the sound signal is of course altered. That's why there is a compressor placed before the BBD: the combined action of the compressor and the expandor is neutral for the sound signal, while the noise level is highly reduced.
This compandor system is too expansive for the common chorus and delay stompboxes, and are found only in costly units. It is clearly one of the qualities of the Chorus/Delay, that makes the difference with its competitors.
Back to what the Rockman Stereo Chorus/Delay does: Stereo, Chorus and Delay...
The chorus effect is achieved by sending the original sound through a 20 to 40ms delay, slightly modulated (e.g. 20 to 25ms) then mixing that with the original sound. The result sounds like two guitars playing together.
The two following samples allow comparing the stereo image of a Rockman chorus with the TC Electronics Stereo Chorus-Flanger, which is supposed to be an excellent pedal. You will make your opinion by yourself...
SR&D added another feature in the Chorus/Delay: the delay of the BBD, usually 20 or 25ms in a chorus, can be doubled and be set at 40ms. This is the limit between doubling (when the ear cannot separate the two sounds) and a delay (the human ear clearly hears two disctinct sounds). This Long-Chorus mode provides a deeper effect than the normal mode.
As for the delay section of the Chorus/Delay, we have here a conventional delay/feedback/level set of sliders. The delay time, as said above, can go up to 200ms: coupled with the output stereo mixer, this allows building all sort of reverbish or slap-back stereo sounds.
Usage, samples and limitations
The main usage of the Stereo Chorus/Delay is of course the classic Rockman chorus sound (for a guitar, a keyboard or even connected to a mixer). The following samples illustrate the wide panel of possibilities of the unit.
The only limitation of the Chorus/Delay is the lack of footswitches: it has only a bypass, a chorus/delay selector and an output mix selector. The other features (long chorus, long delay) are not remote controled.
Collectibility and conclusion
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