E-Mu Ultraproteus, Operation Manual

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49 Chapter 5: Effects Section
EFFECTS SECTION
Stereo Chorus
The function of a chorus device is to thicken the sound or to make one voice
sound like many. The way the effect is achieved is by mixing one or more
delayed versions of the signal in with the original. The delay times used are too
short to be perceived as a an echo, but long enough so that comb filtering does
not occur. In addition, the delay time is varied to simulate the random differ-
ences which occur when multiple instruments are playing together. A slight
amount of feedback improves the effect by creating multiple images of the
sound as it recirculates again and again. The delay times are slightly different
for each channel and the LFO phase is inverted on the right channel to help
contribute to the overall chorus effect. The LFO Rate and Depth settings are
critical to achieving a realistic effect with faster LFO Rates generally requiring
less LFO Amount and vice-versa.
The stereo chorus in the UltraProteus is very similar to the stereo flanger except
that the delay time is longer. The delay times for the stereo chorus range from
13 milliseconds to 52 milliseconds, compared with the 26 microsecond to 6.5
millisecond range of the flanger.
Chorus simulates the effect of multiple instruments playing by creating multiple
copies of the sound using a varying delay time and feedback.
LFO
LFO
Depth
LFO
Rate
R Output
Feedback
Amount
R Input
L Output
Minimum
Delay
L Input
+ -
Delay
13-52 mS
Delay
13-52 mS