Friday 12 June 2020

The Gristleizer

Quite wild voltage controlled modulation and filter circuit by Roy Gwinn dated back in 1975. The most famous user was probably Chris Carter from Throbbing Gristle.

Some mods have been done for this layout  to make more compact and reduce ticking and hiss which is a common problem. Many thanks should go to mictester from FSB and Fuzzdog.

Original had five LM741 single op amps which is merged into a quad and a dual op amp. The dual op amp is in the audio signal path so low noise devices is used like NE5532 or LM833. The quad op amp handles the LFO and a LM324 is reported to have the lowest noise from ticking.

Other mods includes a higher value of resistor connecting to pin 2 of IC1 for higher input impendance and Level control value is reduced from 100k to 10k.

More info about setting the trimmers, schematics and even more mods at FSB , MusicPCB 
and Fuzzdog Pedal Parts

The layout is verified and working really good although there is still some faint ticking, especially in square wave mode.