Cyndustries Buchla Quad Low Pass Gate

Cyndustries Buchla low pass gate

My long awaited Buchla Quad Low Pass Gate from Cyndustries finally arrived. What’s a Low Pass Gate you ask? It’s a low pass filter and amplifier that can be used independently or in combination, and are attenuated by a vactrol. What the hell’s a vactrol? A vactrol is essentially a photocell: light bulb and then a light sensor. The reason you’d want to use one is the gradual brightening and dimming of the bulb – even when it is switched on and off quickly – adds an organic trail, or “ring” to the sound. Optical compressors use this same trick.


Here’s a sound sample I made last night. I use my Q960 sequencer to play a series of notes and trigger an envelope generator that is wired to the Low Pass Gate. The sequence starts using just the gate, then the low pass filter, then both. Since I have four gates on the module I added noise to a second gate and had the Q960 trigger it on a single note in the sequence. It’s interesting that the white noise thru the gate in combo mode sounds like it has reverb on it – though none was applied.

So what do I think if Cyndustries implementation of this module?

  • The over all build of the module is very nice and it seems to work great.
  • I really wish it has resonance on the low pass filters but the original Buchla design didn’t so I can’t really expect it.
  • I ordered it in DOTCOM format and the front panel is DOTCOM, but the power plug in the back is MOTM. Annoying, but I have a spare adapter so not really a problem.

Ultimately I think this is a great module to use in conjunction with the Q960. Can’t wait to brew up some songs with them.

2 Responses to “Cyndustries Buchla Quad Low Pass Gate”

  1. Nice write-up! Say, try this patch again, but this time eliminate the Envelope Generator from the patch… Use raw pulses & gates directly into the CV inputs, (no envelope generator) and slam those Vactrols with a short hot burst to make them ring. If you keep this up in rapid succession then the Vactrol will saturate and act less like a Vactrol BTW.

    If using a square wave as an LFO for example, then narrow the width of it into a short pulse wave to get the shortest “on” time out of the duty cycle. The shorter and hotter the pulses into CV IN then the more like the famous Buchla Banjo Pluc k type sound.

    Just reading that Vactrols and Opto Isolators are being phased out in Europe and then here because of their chemical composition, so you got yours just in the nick of time!

    Best Wishes and Happy Bleeping!


  2. Fitz says:

    Hey Cynthia. Thanks for chiming in! I will try that. The noise hit was generated by a pure pulse (no EG) and it was a very different effect. I’m envisioning four sound sources and four different trigger pulses to make some nice complex sequences.

    I’ve also heard you can get some great wooden type sounds out of them and I want to figure out how to accomplish that as well.

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