Resonance - Lexicon Prime Time 93 Owner's Manual

30
RESONANCE
Higher levels of delay taps A and B in the INPUT MIXER cause longer durations
of recirculated delay. At some point the levels become high enough to cause
resonances, the frequencies of which are determined by the delay times used.
Turn up just one of the delay taps until the resonance effect begins. At
this point resonances will be activated by the audio signal information, be-
ing heard at peaks but otherwise decaying. It is possible to increase the
amplitudes until the
additional stimulus.
runaway tendency but
resonance
11
runs away
11
,
increasing in level without any
The ROLLOFF frequencies can be lowered to minimize this
it can still happen and should be avoided. Resonances
can be used in conjunction with other effects such as doppler pitch shifting,
double and triple tracking, and flanging to create more exotic sounds.
FLANGING
Flanging and, more generally, comb filtering is effected by the PHASE INVERT
·-,
function. Set up a flange with DELAY SELECT A and B at 0 and 1 msec respect-
~
ively: monitor equal levels of both delay taps through the MASTER OUTPUT and
adjust the VCO for obvious effect. Broadband noise can be used as a source
to make the effect even more obvious. Now switch the phase of one of the
delay taps using the INVERT function. Notice the change in tone quality of
the effect resulting from this phase inversion. This can be explained in
terms of the comb filter (which is implemented like the flanging in section
3.2 except without varying the delay with the VCO).
In the first case with no phase inversion, the delayed signal simply adds to
the undelayed signal. This reinforces low frequency components, since the
short delay time represents only a small phase shift. The phase shift in-
creases with frequency until at 500Hz it is 180 degrees causing a null which
is repeated at 1500Hz and at 1kHz intervals thereafter. See FIG. 3.9.
In the second case, the
phase inverted
delayed signal adds to the undelayed
signal. This cancels out low frequency components, but there is less can-
cellation as frequency (and phase shift) increase until a peak at 500Hz is
reached after which nulls occur at 1000Hz and every 1000Hz thereafter. The
inverted comb filter is in effect a low freq. filter which has a higher
cutoff frequency as the delay time gets smaller. This is the reason for
-
-
-
-
-
-
......