CDXL Classic Vactrol


Active member
I know this had been discussed here before but has anyone had success finding the VTL5C4/2? I tried making my own by combining two LDRs and an LED, in a few variations, but haven't ever had success. The pedal turns on and works fine in bypass but when the pedal is engaged, with any combination of LDRs and LEDs, it just sounds the same as in bypass. Any thoughts on where to get the right vactrol or combinations to make your own?


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Active member
What you did should have worked. Is the LED green & diffuse?
I used a 3mm green that was diffused and these LDRs. I tried to fit them in heat shrink but it may not have kept all the light in or out. I connected a leg from each LDR and put that in the middle slot and then the other leg from each into the outside slots. I assume there is no correct orientation with the LDRs? I know the LED is oriented correctly because I took off the heat shrink and it lights up when powered on. This is how I had everything positioned in the heat shrink.


Chuck D. Bones

Well-known member
It's important that the LDRs are fairly well matched, fairly fast, and that they get the same amount of light. For a decent sweep, we want the LDR resistance to get down below 3K when the LED is as bright as this board will make it go. If the LDRs meet this criteria, they will work.