I’ve fallen in love with the Make Noise LxD dual low pass gate (LPG), and wanted to share my love affair with you.

The LxD contains two stages: a VCA coupled with a 12dB/octave, slightly resonant low pass filter based on their MMG (Multi Mode Gate), and a VCA coupled with a non-resonant 6dB/octave low pass filter based on their Optomix. Both inputs have a control voltage (CV) input as well as a “strike” input; the latter responds to the leading edge of a trigger or gate to give a sharp ping to the LPG’s response. The upper 12db section responds faster in general than the lower 6dB section; within the same section, I’ve generally found the Strike input to have a nice sharp spike where the CV input seems to ring a bit more (see the Postscript at the end of this post). The audio out from the 12dB stage is normalled into the input of the 6dB stage, but their CV and Strike inputs are not. For more details, Make Noise has created a very nice PDF manual for the LxD.

As is typical with LPGs, vactrols (LEDs paired with light-sensitive resistors) are used in the control path, which are known for a percussive-style decay that – for better ore worse – doesn’t quite fall to silence. Indeed, if you listen closely to the videos below, you can hear some bleed through when there is audio but not a CV or Strike signal connected to the LxD; vactrol-controlled circuits do get closer to silence when they haven’t been driven for awhile, but don’t count on an LPG as a mute. (Many LPGs today are paired with VCAs to get full muting, if that’s what you want.)

Keeping in mind some of you may be new to LPGs (or even modular synths in general), I spent some time describing the patches and what exactly is going on in both movies.

For these videos and my upcoming course, I color-code my patch cables in the following way:

  • yellow = audio signals
  • white = 1v/octave pitch control voltages
  • blue = other control voltages and modulations
  • red = gates & triggers
  • green = master sync pulses

The first movie introduces the LxD, and uses it in a noise-based percussion patch:


(There are no effects used in either movie, even though the patch with a long release in the movie above sounds like reverb has been applied.)

The second movie uses the LxD in a pitched sequencer patch, where it fills the roll usually reserved for a “normal” VCF and VCA in a traditional East Coast patch:


I strongly recommend using good headphones or speakers to hear just how sharp this thing pings and how deep it thumps.

(Those who are playing module-spotting will notice I just got a set of the Roland System 500 analog modules; I think the VCOs in the above movie sound particularly fat; the Roland 512 looks to be a very solid analog VCO in general. The patch detail that may not be as clear is that I am using the Gate Delay in the Roland 572 module not to delay the gate, but instead to give me control over the gate’s duration to see how the LxD reacts to that.)

I have to say, I really like the sound of the LxD – both for percussion, and just as a full-sounding 2-pole low-pass filter. For me, it’s a keeper: not just to recreate Buchla bongos and other classic West Coast sounds, but also for sharp sequenced and arpeggiated East Coast lines.


In the comments, Jim Aikin rightfully challenged me on whether or not the attack rates were really different for the Strike and CV inputs. So I triggered the LxD with a thin pulse from a VCO, passed DC voltage through it, and looked at the resulting envelopes. The attack times actually seem to be nearly identical – but what’s different is how long each input rings after the initial attack. The CV input rings much longer. This may have been what was fooling my ears into “hearing” a longer attack on the CV input versus the Strike input.

Below I overlaid the two envelopes. The Strike input’s envelope is in yellow; the CV input’s envelope is in cyan (blue):

response envelopes of LxD's 12dB stage

Keep in mind that vactrols will vary from module to individual module, so no two modules may have identical response. Fortunately, I like the sound of my module!