AI Synthesis’ latest module, AI017, is an LPG [Low Pass Gate] complete with those beloved Vactrols in the tradition of the famed Buchla 200 series LPG, and it does its much-revered predecessor proud, though AI Synthesis has thrown some of their own flair into the mix, giving the LPG a little more depth.
Having had a Buchla Music Easel I’m pretty familiar with the characteristics of a Buchla LPG, as well as what to expect from it. I’m always amazed at how much you can get with so little, a trait that is evident in the output section of the Easel where the LPG resides, with just two sliders and a toggle. I was interested to see what kind of action I could get out of 017, which has a bit more than that. For those unfamiliar with a Low Pass Gate, in most modules it’s a combination VCA/VCF where the frequency and amplitude are both affected by the same control voltage simultaneously, so as the amplitude drops, the high frequencies get filtered out and the audible range of the signal decreases on both fronts. This gives it an amount of realism, that being an emulation of acoustic instruments [e.g., bongos, etc.]. One of the quirks of this is that sometimes the input signal can leak through and be heard even with the control voltage at 0 volts. 017 carries on the traditions of LPGs [and the Vactrols], but adds a way to quiet the circuit completely.
There are three knobs on 017: RES, DEPTH, and LEVEL, as well as a multi-position toggle to switch between VCF/LPG/VCA mode. There’s also an on/off toggle for DEPTH, 2 CV inputs [CV1 and CV2, which has an attenuator for the input signal] and an INPUT with an attenuator, and an OUTPUT. All of this resides on a simple faceplate—either black or silver—with easy to read text and minimal flash. AI Synthesis modules all have an understated, classic look and they haven’t strayed from this since day one, or module 01.
The RES knob only has an effect while 017 is operating in VCF mode, so know that first and foremost [so you don’t think your module is broken], and there is also a resonance gain trimmer on the back of the module to tailor that to taste. The DEPTH control operates similarly, in that if the DEPTH toggle is off, the control will have no effect. DEPTH is an AI Synthesis update to the traditional LPG circuit that adds negative bias so that the base voltage level can go lower than it normally would, so, as mentioned, there will be no bleed through. DEPTH can also help shape the overall sound, though I found the usable range in this facility to be rather small in some circumstances. Strangely, DEPTH has the most life-like characteristics of 017; there would be times when I dialed in what I thought was the perfect amount of the effect, only to have it eventually wither away into inaudibility, like putting a pillow over your patch Goodfella’s style. Cue Joe Pesci.
The LEVEL control has multiple uses, as it operates as a volume control in VCA and LPG mode if no CV is patched into CV1, and it’s your LPF sweep knob when in VCF mode; though don’t expect 017 to be your go to Moog type filter, it’s not going to suck up the trash you have on the floor. When in filter mode, with no RES, the LEVEL knob only garners a reduction of frequencies in the final 10% if turning CCW. With the RES turned up, however, 017 comes alive with great distorted saturation/feedback at the RES peak.
There are definitely sweet spots on 017, like with RES at about 95% and the DEPTH at anything less than 85%. This filter can get a great raspy, sci-fi, alien radio type of growl, and putting a really snappy envelope into CV1 and a fast moving sine wave into CV2 with the RES and DEPTH both high and the LEVEL at about 7:00 while in VCF mode gave staccato bursts of bird whistles, while flipping the switch into dual LPG mode and upping the octave gave a hollowed out bell-like sound with the beautiful roundness expected of the Vactrols.
In strict VCA mode, 017 acts as it should, and can be modulated as a typical VCA with voltage going into CV1 with the LEVEL knob being a mixture of the VCA and through signal. I have to admit to really enjoying the sound of the VCA, and having the added DEPTH is much appreciated. You can dial in just enough DEPTH so that the sound barely gets through, and the interplay between LEVEL and DEPTH made for some interesting percussive hits and sonic possibilities, some of which reminded me of the dying 9-volt battery trick that can be used on some fuzz pedals to get a fuzzy, broken up sound that’s different than when a full 9-volts is applied.
017 really benefits nicely from a versatile and highly tweakable envelope generator with which to pair it with. In my testing I was giving Schlappi Engineering’s new Boundary a run through, and the envelope, the SLEW portion of that module, complemented 017 nicely, feeding all sorts of envelopes into CV1 of 017. Throwing additional modulation into CV2 can give your patch more dimension.
As mentioned previously, there are some knob settings/combinations to where there would only be a small percentage of usability in the range and that sometimes threw me off. On the flip-side, the more I used 017, the more I started to understand its quirks and grew to really like what it brings. There’s a nice combination of controls that separate this module from its contemporaries that are content to simply emulate the Buchla LPG, not bringing anything new to it—not a bad thing or a crime, either, especially when a classic is involved, but the additional controls on offer with 017 makes it a versatile module with excellent sculpting ability, especially in the percussive realm. It’s the DEPTH control that sets this module apart, and in combination with the Vactrols ability to bring about the much appreciated ringing and bongo sounds of the original LPG, make 017 worth the ink on its faceplate.
Available assembled, in DIY kit form, and points in between, the test module came fully assembled so I can’t comment on the difficulty of the build, but according to the AI Synthesis website, they rate it a second-module build, so if you plan on DIY’ing this and have some experience you should be in good shape.

8 HP +12V 19mA -12V 17mA
Price: From $15-$115

aisynthesis.com