Rolling your own vactrol

[Timko]

More questions .

I am using the Tayda LDRs, which have a frequency of 650nm.

http://www.taydaelectronics.com/photo-conductive-cell-resistor-ldr-650nm-radial-ke-10720.html

On the visible wavelength spectrum, this is closest to red, which I used in my first homemade vactrol. However, a lot of people are using yellow in some of their builds, which appears closer to 570nm.  Is there a reason to opt for this?  Is it to create the response of a particular commercial vactrol?

[midwayfair]

In all seriousness, most people when they pick an LED for a vactrol are not doing it for any reason except their gut feeling based on tonal comparisons made without a proper A/B test. I'm not saying everyone's like this, but most people are just saying, "I used such and such and I liked it better." Or going by what the last person did. Changes in the current consumption of the LED can also affect the sweep of the LFO independent of the LDR's behavior; I have intentionally chosen blue for at least a couple boxes because it made the cycle asymmetrical.

Another thing to consider is that raw brightness can trump frequency spectrum. An LED that draws more current will often be brighter in terms of actual lumins (not just "humans see green-yellow best"). But you can, of course, increase the current through a red LED if you drop the current limiting resistor some. And vice versa.

[Timko]

Awesome explanation!  I believe I'll socket the LEDs on this phaser and see what happens.  I'll also revisit the schematic to look at the CLR.

[rullywowr]

It means you can test it in a room with the lights on.  An LDR is sensitive enough in a darkened room that flickering from the TV in a room with the lights off can set it going so you pretty much need to mount it up and close the box to test it.

IU've rolled my own in the past.  Just push the LED into shirnk wrap from one end, and the LDR in from the other.  Shrink the wrap.  i don't think i bothered sealing the ends as I had enough overhang.  Vactrols are way easier.

Bean pointed out one time that you can use BluTak (poster putty) to help test Vactrols in a room with the lights on.

To roll your own, you can simply use some dark shrink tubing.  Some will use a bit of super glue to attach the LDR to the LED.  I am a big fan of using flat top LED for this as the flat surface mates with the LDR perfectly.

Some builds I don't even bother with the shrink tube as it is pretty dark inside one of those enclosures with the lid on.   

[Timko]

Hey, back from the dead!  I figured I would revive this post to keep the DYI Vactrol stuff together.

I was curious if there's some reason I would choose a 3mm LED over a 5mm LED.  Inside a vactrol, which shields the light to about 5mm, it doesn't seem like there would be that large of a difference.  But I've only done 3 pedals with my own rolling, and figured someone had more experience to share.