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| This
module is a dual utility LFO offering manually variable
wave shapes. Standard waveshapes are falling ramp variable
through triangle to rising ramp, and variable pulse
width. A fixed square wave is also available, as is
a combination waveshape that is variable between the
TRI/SAW output and the SQUARE. This is a MIX not a morph.
Two switches allow the variable outputs of the two LFOs
to be intermixed. |
The
Utility LFO is based on the standard integrator/schmitt
trigger oscillator core. Two pots in the integrator
charge path allow for the adjustment of speed, and along
with two diodes, for the adjustment of
charge versus discharge time. Changing this ratio will
allow the TRI/SAW output to be adjusted from a falling
ramp through triangle to a rising ramp. At the same
time, the output of the schmitt trigger will reflect
this in the length of its output pulse. |
A
0-volt referenced comparator connected to the output
of the integrator generates a square wave as there is
always an equal portion the ramp/triangle wave above
the 0-volt reference, though adjustment of the shape
of the ramp/triangle wave does change the phase of this
square wave.
Following the comparator is a buffered voltage divider
to bring the square wave down to a more suitable level
and also to drive one side of the variable output mixer
pot. The other side of the variable output mixer pot
is connected directly to the integrator output. The
variable output is buffered and used post mixer by another
op-amp. |
| The
JOIN switch interconnects the two VARI outputs by swapping
their ramp outputs with each other, so that each output
is a combination of that LFO's square wave with the
other's ramp. |
The
SWAP switch reverses the outputs of the second LFO so
that (when JOIN is on) one VARI output
is a combination for both square waves while the other
is a combination of both ramps. When JOIN is off, SWAP
merely reverses the direction in which the second LFO's
VARI knob works. |
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