Low Pass Gate


VC Resonant Low Pass Gate REV 1.5

A version of the Buchla Low Pass Gate. This module includes Voltage Control of the Mode and Resonance amount. There is no switching to select mode. Voltage control varies the mode from VCA/VCF mode smoothly through VCF mode to highly resonant VCF

Build Notes: The builder can choose to build either a Fast or a Slow gate. VTL5C3/2 is used for a fast response and a VTL5C4/2 is used for a slow response. 2 Single Vactrols can be installed in the filter section where the board calls for a dual. See the pictures for a guide on how to do this. The LEDs should be wired in series, and one end of each photoresistor should go into the center hole. A single Vactrol is used in the VC Mode circuit. Regardless of the type used in the filter section, a VTL5C3 should be used for the VC MODE circuit. No other vactrols were tested in that position.

LPG Build Notes


Current build is Version 1.5

Download documentation here:LPG REV 1.5 Documentation

1 resistor should be substituted - the reistor labeld 220K on the silk screen layer should be 330K


Download documentation:LPG V1.0

Version 1.0 has several modifications needed to correct for the effect of Light/Dark adaptation in the resonance Vactrol

Please read all documents befor ordering parts and building



Using single Vactrols in the filter section. 2 Vactrols will need to be stacked up. The LED side should have the 2 units is series. The photoresistors should be hooked up so one side of each Vactrol goes to the center hole.