# Vactrols are magic!

**URL:** <https://lookmumnocomputer.discourse.group/t/vactrols-are-magic/3008>\
**Category:** DIY STUFF\
**Created:** [February 22, 2021, 11:26pm UTC](https://lookmumnocomputer.discourse.group/t/vactrols-are-magic/3008 "2021-02-22T23:26:23Z")\
**Posts on this page:** 1\
**Showing post:** 10

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**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\
**Post date:** [May 13, 2021, 9:44am UTC](https://lookmumnocomputer.discourse.group/t/vactrols-are-magic/3008/10 "2021-05-13T09:44:08Z")

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Hey @analogoutput , would you mind explaining how you came up with this circuit? 🙂 I read a bit on [northcoast synthesis](https://northcoastsynthesis.com/news/leds-and-analog-drivers-for-them/) and found that your circuit is similar to (D), but I don’t understand the two diodes D1 and D2 (I assume it’s some kind of reverse voltage protection, but couldn’t that be done with a anti-parallel diode to the LED?)  
Why the additional 1k resistor? And tC1 is for some kind of stabilization/filtering?

![](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/d43e8e3c1fd1294615dcba522a1d2cb60e73e996.png)

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