Data
21.
TECHNOBABBLE
e Multiwave Mega is a analog / digital hybrid.
On the analog side with got the preamp, sample and hold and
the resonant lowpass lter. On the digital side we have a
microcontroller that handles the oscillators, lter control, the
LFOs and the buttons.
It uses a CMOS based preamp stage that converts the guitar
signal into a square wave and then multiplies the frequency by
64 using a Phase Locked Loop together with a binary counter.
is is needed so that the microcontroller doesn’t have to do
anything too demanding using timers. It simply uses an
external interrupt to cycle through the waveshape arrays.
e oscillators are wavetable based, which means that every
waveshape is stored as an array of numbers that represents
pwm duty cycle (voltage levels) for a single waveshape cycle.
It has a 6-bit resolution (64 steps) for the oscillators and the
LFO, and a 7-bits resolution (128 steps) for the envelopes.
It has a total of 35 wavetables stored on the microcontroller
for the dierent waveshapes (and one for each detune setting)
with a few unique wavetables for the envelopes and the LFO.
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