The end of vactrols

It just came up in the pictures thread, //// pictures //// - vactrols are on the way out. I’ve bought into the idea of vactrols as a “design choice that makes things sound smooth and organic.”

I know they can be modeled digitally. Vactrol-boosters like Make Noise are starting to release vactrol-free modules (dynamix as an example, MMG is out of production). Should this feel sad? I feel sad. Vactrols have been part of the design of most modules in my rack. Are they hype? Should I not be sad?


also, isn’t it possible to diy vactrols? photo-resistor + led?

are photo-resistors on their way out, too?

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Rationally, I’d say it’s a sane decision.
But emotionally, I love the sound of a ringing LPG.
I love the 292, I love its children, the QMMG, the Optomix.
There’s nothing that sounds like that that I know of.


Given the above, I’m more than willing to give up the gloriously smooth response of vactrols for the greater good. I eagerly anticipate additional reckonings around the cruddy minerals that make up my iPhone and laptop. Hopefully friendlier alternatives will appear in the next decade!


anyone have or have heard the Pittsburgh Dynamic Impulse Filter? the engineer (disclosure: I’ve known him for 20+ years & he rebuilt an Arp Odyssey for me before he took over as main builder there) spent 2 years modeling a vactrol for it, all analog.


Fortunately there’s more LPGs without vactrols (disclosure: I work for them)


(yes (cadmium ones are in 20 characters))

And it sounds fantastic. I had two Optomixes, now I have one and one Natural Gate.

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I was surprised last week when an American pedal designer refused to sell me (London) a pedal that involved a vactrol, saying that ‘the components I use are illegal in Europe’, which I’m pretty sure they’re not.


I’m not an expert, but if you google “vactrol rohs” you’ll find a lot of people claiming that vactrols are in fact not legal to sell in the EU, due to the cadmium in the LDR.

My grandmother’s dementia was likely caused by keeping porcelain painting brushes wet in her mouth as she worked over the decades. Cadmium red no longer exists for this very reason.

It looks, however, like in the EU there was a bit of back and forth on Cadmium pigments, in the end deciding in favour of Cd, by reason of not having enough evidence to back what would otherwise end up as an arbitrary ban, so paints are still on the market…

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Interesting. I hadn’t realized that. I suppose she retired from her painting during the period when the ban was active.

So glad I have most of the vactrol gear i might want already.

and it’s not just modular. Where would I get that amazing Morley Wah sound from without photoresistors?!

And not to go off topic too much, but it’s the same with rosewood in guitars. That’ll be disappearing from most guitars over the next few months if it hasn’t already. You can no longer get a Fender Standard P bass with a rosewood fingerboard new. My bass was so cheap, and yet uses a material we’ll now consider luxury.

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are the isms lpgs’ vactrols made from anything special? perhaps @Galapagoose or @tehn can provide a bit of info. all three of mine seem remarkably well-matched.

Especially if you think that photoresistors were exempt from RoHS because of difficult substitution, but the exemption expired. In 2013.

Sorry, I’m a bit naive on the subject, but what makes it so difficult to try and model these things digitally or in software?

420 go to used electronics graveyards and harvest opto-isolators every day.

The math may seem a bit heavy, but the circuits are pretty simple.



buyin’ up Meng Qi dplpg’s like canned goods and water…

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