Jitter help?

i’m using vcv rack to create a super slow LFO to control a light that moves with CV. ive used vcv rack to do this effect for years with no issue. lately i see jitter, the jitter is super obvious because the light should be moving slowly, and it is, but it jitters back and forth from the spot its supposed to be on by an inch forward and back.

when i monitor using voltage meters in vcv rack the voltage is rock solid, no jitter. it seems to happen mid patching. i’ll add two frozen wasteland super slow lfos set to a minute cycle, and it looks perfect. then ill modulate the phase of one of them with a bog lfo, and then the jitter will happen. then ill create a new patch with just two lfos and nothing modulating them, and i see jitter. then i restart and the jitter is gone (but that trick doesnt always solve it).

i have a 16" M1 macbook with 16GB ram. messing with threads and block size doesnt seem to help. i wonder if perhaps frozen wasteland or bog can be buggy or introduce something weird, and using other modules may solve the issue? but i dunno… its really strange…

i dont think the issue is with the light or anything besides the computer/vcv rack. i could be wrong, but it works with other laptops. i dont really use this laptop for anything else though, not sure what could have changed.

Can you expand on this part a little? Is this a real-world light bulb outside your computer? And how do you get the voltage signal to it?

maybe the samplerate of VCV or the macbook? just a guess

its a club laser lighting unit. i use an audio dac (usb streamer) to control it using cv

is there such a thing as “more reliable” or “less buggy” modules that do slow lfos? im wondering if i should stop using frozen wasteland super slow lfo and switch to Shapemaster or something. does anyone know which module in this category would be the most reliable for bugs and 1 or 2 minute long cycles

Side note: sounds like a cool setup!

If I’m reading you correctly, you’re seeing jitter in the light but not VCV Scope? If so, that’s very strange.

In any case, I’d expect Shapemaster to be rock-solid, but I’m surprised that the FW/Bogaudio combination is giving you an issue. If you post a patch (particularly the one that that sometimes but doesn’t always fix itself on restart) I (and others I’m sure) would be happy to take a look.

Also–it looks as though USB Streamer has DC-coupled outputs, but are you possibly blocking DC in the Rack Audio module? Bear in mind that Audio-2, introduced in Rack 2, has DC blocking on by default (unlike -8 and -16). This would cause unpredictable behavior with a LFO that might, just might, manifest as what you’re describing. It’s a long shot but I wonder if this might be it, because processing done by Audio-2 would be the one thing that wouldn’t show up in the scope…

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I would first try to isolate whether the problem is happening inside VCV Rack or in the USB audio DAC.

Is there also no jitter in the VCV Rack Scope when you experience the problem controlling the laser? Or does the scope show the jitter then?

If you are running identical versions of VCV Rack and all the modules, on the same operating system, using the same patch file, and the problem happens on one computer but not others, I would start suspecting some random glitch in your audio DAC.

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As you probably know, the DC Blocker in Audio-2 (-8/-16) is here, and that’s what you want to make sure is off:


really appreciate the help from everyone on this forum!

im aware of the dc blocker…

i dunno whats up, i think its my interface or something non-vcv rack related…

Yeah, it’s really strange. What do you hear if you move the LFO up into audio rates and just listen to the output through headphones or speakers? Anything that would mess up the light that badly would almost certainly show up on a listening test.

Do you have an alternate CV source that would let you test the light? It seems like an input or motor malfunction would need to be ruled out, and those could show up intermittently as well.

Does the issue show up if it gets a fixed CV from, say, Count Modula’s “Manual CV Generator”? Or is it only from changing CVs?

Is there some threshold voltage at which it first appears?

I have to test more. I’ll look into this. Haven’t tried static fixed signal yet. It seems to only glitch once I start modulating the phase of the super slow lfo with a big quadrature lfo. I wonder would a VCV Log file help figure this out

The log file won’t help you with anything about CV and signal paths – it’s all about the mechanics of the module management. - loading and unloading, autosave, etc. If you want to inspect signals, that’s what Scopes, Spectrum Analyzers and that ilk are for.

I always use VCV’s 8vert as a test DC source…