IN SUM
(mixer) SPIN
(OSC/FILTER CORE)
GRIND -> SPIN
(FILTER IN)
IN
OUT
FM1 FM2
SPIN
(COARSE) FINE
V/OCT
LOW PASS HIGH PASSBAND PASS
INVERTED
BAND PASS
0º 90º 180º 270º
OSC
FILTER
INJECT
AUDIO
INPUTS
FREQUENCY INPUTS
OUTPUTSMODE
DAMPING
sliders sum with cv inputs
to provide voltage control
over vcas
COMPARATORS
osc/lter outputs are compared
against an external input
creating four square waves
GRIND
- - - -
square waves are subtracted
from input signal
HOW IT WORKS
TWO PARTS: SPIN & GRIND
SPIN
This is a quadrature sine wave oscillator. That means it is as oscillator that outputs four sine waves
ninety degrees out of phase with each other as shown:
Internally the circuit is very similar to a state variable lter except there is an always-on positive
feedback path optimised for clean oscillation. We can cancel the positive feedback with a negative
feedback path (this is what the DAMPING knob does) and stop it from oscillating.
When enough of the grind signal is fed into the SPIN section it overwhelms the oscillations and
starts to lter (it will do both at the same time sometimes.) The SPIN outputs then become the
familiar LOW PASS, BAND PASS, HIGH PASS, and an INVERTED BAND PASS.
GRIND
This section consists of four comparators, four vcas, and a mixer. Each SPIN output is compared against the
input and depending on which one is higher in value a square wave is created. These square waves are fed
into the VCAs and their amplitude is controlled by a sum of the GRIND CV INPUTS and the GRIND SLIDERS.
These signals are then subtracted from the input signal creating waveforms like these:
As the GRIND -> SPIN knob is turned clockwise these forms paths will transform into voltage controlled
nonlinear feedback paths and by mixing them together unpredictable shapes are formed.
ALL PASS
(PHASE SHIFT)
