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Originally Posted by
mekanik
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dont you mean photoresitors?
then there is also phototransistors and photodiodes.
at least thats what i read on wikipedia.
Anyway i'm fairly certain devices like vactrols will keep existing, and probably with all kinds of flavors and responses. hell, you can even make these yourself. to get different responses you can substitute the led for a light bulb/neon bulb/halogen for example.
I wouldn't worry.
The problem is light dependent resistors (LDR)
Photo resistor - Light Dependent Resistor (LDR) >> Resistor Guide
Which have not been popular for years in most electronics because of their very loose tolerances. LDR's use cadmium and components like vactrols had an RoHS exemption that expired in 2015.
The price has gone way up over the past decade, and production is low.
For companies that need RoHS compliance, E.G. new designs this is a problem.
For the EU, all electrical/electronic equipment, cables, and spare parts with compliance required by at latest mid 2019. It may happen earlier for some components but it will block a CE rating, and Europe is a large market. It may also impact California which has adopted RoHS.
This reduces what was already a small market, and you will see that most parts are "no longer manufactured"
http://www.newark.com/excelitas-tech...vrms/dp/43F885
That will become more and more common, and the newer devices tend to lack this behavior from my first link above.
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Another interesting property of photo resistors is that there is time latency between changes in illumination and changes in resistance. This phenomenon is called the resistance recovery rate. It takes usually about 10 ms for the resistance to drop completely when light is applied after total darkness, while it can take up to 1 second for the resistance to rise back to the starting value after the complete removal of light.
For Compressors or Buchla style Low Pass Gates this is an issue for traditional circuits.
Products like Make Noise Dynamix and 0-coast show you can still do very interesting things, but if you are a fan of Buchla or even the MS20 vca/vcf sound you may want to prioritize picking up a few of these items.
It is still possible that they may find some alternative, or that a new exemption may come in place. But even if you don't live in the EU these will probably become more expensive and harder to find. Technically it is illegal to ship a optical compressor to California right now too, but I think that companies are ignoring this, and some will categorize the parts in to areas with exceptions. My understanding is no device with an LDR in it has been found to be compliant when under review and a few component manufactures were found to have committed fraud when they sold products that they did claim were compliant.
As this use is actually taking advantage of what is a fault or at least a limitation for most circuit designs I wouldn't expect something to come from off the shelf, so it will have to be the fairly small music industry that finds solutions.
To be 100% clear again, this isn't a huge issue if you aren't looking for the exact behaviors provided by vactrols and other LDR based components. And for at least the next few years there is probably enough old stock or take offs for those who aren't in the EU. I don't know enough about the EU to advise for people who live there, I am just noting the impact world wide.