Endangered Audio Research The GRISTLEIZER

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via this auction
"These units are hand made and are awesome modulator/synth units for guitars, synths, keyboards, vocals (if crazy enough).

It also has an output for a expression pedal that you can adjust the frequency "on the fly" (very cool)..

some more info on the unit:

THE GRISTLEIZER IS AN ANALOG SYNTHESIZER EFFECT UNIT FOR USE WITH ALL TYPES OF INSTRUMENTS AND SIGNALS. THE VERSATILE LFO CAN MODULATE SIGNALS, AND WITH THE OTHER CONTROLS CAN OFFER AN INCREDIBLE VARIETY OF SONIC POSSIBILITIES. FROM FILTER EFFECTS IN VCF MODE TO UNIQUE TREMOLO AND RING MODULATION LIKE SOUNDS IN VCA MODE THAT RANGE FROM SUBTLE TO UNRECOGNIZABLE.

THE GRISTLEIZER IS THE LEGENDARY EFFECT USED EXTENSIVELY IN THE MUSIC OF THROBBING GRISTLE BY ELECTRONIC MUSIC VISIONARY, CHRIS CARTER WHO ADAPTED THE CIRCUIT FROM A DESIGN BY ROY GWINN AND BUILT THEM FOR THROBBING GRISTLE.

FEATURES
LFO WAVEFORM SELECT: 4 WAVEFORMS TO MODULATE YOUR SIGNAL IN VCA OR VCF MODE

FREQ: CONTROLS THE FREQUENCY OF THE LFO FROM .25HZ (1 CYCLE IN 4 SECONDS) TO 100HZ

DEPTH: CONTROLS THE LEVEL OF THE LFO MODULATION APPLIED TO THE SIGNAL

BIAS: CONTROLS THE INTENSITY AND GRIT OF THE MODULATION ON YOUR SIGNAL IN VCA MODE AND IN VCF MODE, SHIFTS THE CENTER FREQUENCY OF THE BAND PASS FILTER

LEVEL: CONTROLS THE OUTPUT LEVEL OF THE EFFECT, CAPABLE OF LINE LEVEL SIGNALS

LED: VISUALLY INDICATES THE FREQUENCY OF THE LFO

MODE FOOTSWITCH: SELECTS EITHER VCA OR VCF MODE FOR AMPLITUDE MODULATION IN VCA, OR FILTER MODULATION IN VCF MODE

BYPASS FOOTSWITCH: THIS IS A TRUE BYPASS SWITCH. WHEN BYPASSED, SIGNAL PASSES DIRECTLY FROM INPUT TO OUTPUT

INPUT: ACCEPTS LOW LEVEL (INSTRUMENT) TO LINE LEVEL SIGNALS FOR GREATER FLEXIBILITY

OUTPUT: DRIVES LOW LEVEL TO LINE LEVEL INPUTS DEPENDING ON LEVEL CONTROL"