Kurzweil K2661, Musician’S Reference Manual

Page: 142 / 500

10-60
KDFX Reference
KDFX Algorithm Specifications
the realm of chorusing, where the ear begins to perceive the audio output as nearly two distinct signals,
but with a variable time displacement.
Figure 10-21 Comb Filters : Solid Line for Addition; Dashed Line for Subtraction
The heart of the fl anger implemented here is a multi-tap delay line. You can set the level of each tap as a
percentage of the input level, and the level may be negative (phase inverting). One tap is a simple static
delay over which you can control the length of delay (from the input tap). Four of the taps can have their
lengths modulated up and down by a low frequency oscillator (LFO). You are given control of the rate of
the LFOs, how far each LFO can sweep through the delay line, and the relative phases of the LFOs. (i.e.
Where is the LFO in its sweep: going away from the input tap or coming toward it?)
The fl anger uses tempo units (based on the sequencer tempo or MIDI clock if you like), together with the
number of tempo beats per LFO cycle. Thus if the tempo is 120 bpm (beats per minute) and the LFO Period
is set to 1, the LFOs will pass through 120 complete cycles in a minute or 2 cycles per second (2 Hz).
Increasing the LFO Period increases the period of the LFOs (slows them down). An LFO Period setting of
16 will take 4 measures (in 4/4 time) for a complete LFO oscillation.
You can set how far each LFO can sweep through the delay line with the excursion controls (Xcurs). The
excursion is the maximum distance an LFO will move from the center of its sweep, and the total range of
an LFO is twice the excursion. You set the delay to the center of LFO excursion with the Dly parameters.
The excursion and delay controls both have coarse and
fi ne adjustments. By setting the excursion to zero
length, the LFO delay tap becomes a simple static tap with its length set to the minimum tap length. Note
that modifying the delay to the center of LFO excursion will result in a sudden change of delay length and
consequently, a discontinuity in the signal being read from the delay line. This can produce a characteristic
zippering effect. The Dly parameters should be as long as the Xcurs parameters or longer, or else changing
(or modulating) the excursion will force the center of LFO excursion to move with the resulting signal
discontinuities. The static delay tap does not suffer the zippering problem, and changes to its length will
1 0
0
1 0
2 0
Amp
(dB)
Frequency