7-14
Rev 2.2, 10/31/94
will fall by 8 dB for every 1 dB of input change below threshold. A release time of 1000
milliseconds says that it will take 1000 milliseconds for the output signal to decay from its
initial value. The
R
ATIO
parameter deals with the slope of the input vs output gain relationship,
independent of time and the
R
ELEASE
parameter deals with the rate-of-change (in time units) of
the output signal when it transits the two points (initial attenuation and ultimate attenuation)
as determined by the ratio setting.
7.5.11 Delay
The delay section of the 601 uses two delay lines having separate inputs and separate outputs.
The outputs drive a lowpass filter that feeds the output mix and the feedback controls. Each
feedback signal mixes with the input signal at the delay line input of the opposite channel (the
feedback is cross-coupled). A signal flow diagram may be found in Figure 7-3.
The delay times of the delays may be adjusted independently or ganged together. The feedback
factor, lowpass filter frequency, delay time rate-of-change, level-related rate-of-change, and the
wet-dry mix are independently adjustable. Finally, the delay time of the two delays may be
modulated with the rate, waveform, and depth parameters being adjustable.
The delay modulation source is either a sine-wave generator, triangle-wave generator or a
random number generator. The
R
ATE
parameter sets either the sine/triangle-wave frequency.
or the random number generator's update rate. The depth control limits the range of the delay
time modulation. Holding down the
R
ATE
button changes the delay modulation source.
All of the previously mentioned parameters may be programmed via MIDI.
7.5.11.1 Echo effects
Creating an echo consists of delaying the input signal by some amount, then adding the
delayed signal back to itself. This creates an echo having one repeat. To create this type of
sound, set the
M
IX
to 50%, set the
D
ELAY
to 330 ms for both channels, set the
F
ILTER
to 18
kHz, and finally set the
F
EEDBACK
to 0. You (into mic): "Hello." 601: "Hello Hello." Experiment
with different delay times. What does it sound like when the delay time is quite short, say
around 10 ms? What does it sound like when the delay time is mid-range, say 40 to 80 ms.
Now experiment with different mix settings. Listen in stereo and make the two delay times
slightly different. Now try making them radically different. Try using
duAL
mode to sweep the
different delay times.
You create repeating echoes by recirculating the output of the delay line back to its input. On
the 601 set the
F
EEDBACK
to
P-10
, set the
D
ELAY
time to 330 ms. Now speak into the mic. You:
"
Hello
." 601: "
Hello
Hello
Hello
Hello
Hello
Hello
..." Higher feedback settings increase the
number (and duration) of the echoes. Be sure that you try varying the wet/dry mix as well as
the feedback and delay times.
7.5.11.2 Flanging
It's Audio history time. The term "flanging" came about because the effect was originally created
by using two three-head tape recorders (30 years ago, that was how we created delay), inputs
paralleled, outputs mixed. Then the engineer held his thumb on the reel flange of one machine
to slow it down slightly (which changed the time delay). Varying the pressure on the reel flange
changes the effect. That's more or less what happened when The Small Faces made "Itchykoo
Park," about 25 years ago.
Flanging is nothing more than comb filtering. The modulation oscillator replaces the thumb on
the reel flange. On the 601, you create flanging by choosing a very short
D
ELAY
time, 0.5 to 2
milliseconds, set the
M
IX
at 50%, set the modulation
R
ATE
at 1, set the modulation
D
EPTH
at
100. You should hear a hollowness (the jet plane sound) that changes with time. Increasing the
amount of
F
EEDBACK
makes the effect more pronounced. Changing the
F
EEDBACK
polarity/phase shifts the comb frequencies. Increasing the delay-time Rate-of-change (
rt
) by
holding down the
D
ELAY
button until the display reads
rt
smooths out the transitions and
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