Angle Grinder is a quadrature sine wave oscillator or filter and distortion effect.

The function of the Angle Grinder depends on both the position of the knobs and the presence of an input signal.

• Quadrature sine wave VCO with four phase related outputs: 0°, 90°, 180°, 270°
• HIGH range from 10Hz to over 20kHz
• LOW range from 0.1Hz to over 500Hz
• Tracks volts per octave at the V/OCT input
• FM1 is selectable linear or exponential FM via jumper on back
• FM2 is additional exponential V/OCT jack
• With no input GRIND section provides voltage controlled harmonic content
• With input GRIND section compares each phase against GRIND IN signal
• Each slider subtracts the compared signal from the input signal, creating complex waveshapes
• When GRIND is fed into the SPIN section the outputs become a state variable filter
• DAMPING counteracts the oscillation and allows an external signal through
• When filtering the four phase related outputs are: LOW PASS, BAND PASS, HIGH PASS, and INVERTED BAND PASS
• When filtering the GRIND section is a nonlinear feedback network for harsh and unpredictable timbres
• The four phase feedback paths can be separately voltage controlled
• The INJECT jack can be used as a second input for either audio or CV, bypassing GRIND
• All analog OTA based design