LPG.audulus (9.7 KB)
I think this is the version I have. I’m safe, right?
Yes. This design uses the one pole design from the filter tutorial and it’s fine. I didn’t use a one pole in the LPG that was included with the demo because I wanted something resonant. I use the bi-quad because it’s fairly low CPU but I was playing around with it yesterday and it kind of went off the deep end. BIquads don’t handle rapid modulation of parameters particularly well and it seems they’re particularly poor at very low frequencies. I’m going to try some other filter types this morning.
BTW, you could substitute the low pass node for this filter and save some CPU. I’m pretty sure it’s the same code running, but because it’s compiled it’s more efficient. Here’s one with the Hz to alpha formula built in.
First Order Filters.audulus (3.6 KB)
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I’m revising the LPG. I’ve been using the following:
Buchla Low Pass Gate.pdf (627.7 KB)
I’ve got the filter mostly complete but I’m debating some of the details. The emulated Doepfer unit I have from Softube is resonant in all modes whereas the Buchla unit was only resonant when switched to LP only and the resonance wasn’t adjustable. I’m inclined to follow the Deeper unit as far as controls since I like the resonance. Should I have a switch for LP, VCA or both like the Deeper and Buchla units or just do both only?
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I would think switch, to make the users able to choose, but then again…choices can sometimes be the worst enemy of an artist (specifically myself lol) when they get caught up in a loop of tweaking options and testing, instead of just using what is there and creating. So much of my production time is wasted using complex tools and trying to get the right sound. I actually gave my old OP-1 a try, and I find that I am getting more done with the limitations imposed. Maybe I am a unique case though. Just my thoughts. I hope you are enjoying your weekend!
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Those are good points. Buchla is known to have given a lot thought as to which parameters to expose and also their ranges to find a balance of range and usability since he recognized that untethered flexibility can be paralyzing.
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I wasn’t sure if that was a rhetorical question. I think the combination of LP/VCA is pretty nice sounding personally, but multi-mode gates are definitely a thing. The latest QMMG was released with a continuous sweep that goes through VCA-Both-LP-HP sort of like a sem filter after you go through “both.” That might be fun 
I gotta say I am loving my digitakt for much the same reason.
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I have 2 combo LPG modules in the Volca Modular, and it sounds great. On the other hand, the VCA of the Microvolt 3900 has a traditional setting and switch options for LPG mode with 2 attenuators for dynamics and harmonic control, plus a switch to enable ‘pluck mode’, which makes the gate or amplifier momentarily let everything through and snap shut rapidly on the sound and providing an effect that resembles a plucked string. I think the options for switch or no-switch each have their merits. Ultimately, @stschoen is a very talented programmer/designer, and I will be happy with whatever he decides is best for his creation
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I discovered the amplitude knobs for oscillator 1 and 2 were reversed. I fixed that and replaced the LPG with an improved version.
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I actually meant to make a comment about the amplitude knobs and apparently failed at posting it! Good on ya! 
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Found another bug with the sync circuit. I rearranged the knobs and improved the tuning. 
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