Rolling my own vactrol

[Guybrush]

I've been searching for DOD 440 builds on the forum as I'm about to build one myself and came across this old post from Jimilee - https://www.madbeanpedals.com/forum/index.php?topic=26019.msg252490#msg252490


I have the VTL5C4/2 vactrol asked for in the BOM, but can see that in the link above, Jimi successfully rolled his own. I'd like to give this a try just for the hell of it but have a couple of questions I hoped someone might be able to help with.

Here goes - The VTL5C4/2 has 3 legs on one side and 2 on the other - 5 legs in total. If I'm making my own from an LED (2 legs) and an LDR (2 legs) then that leaves an unused pad on the PCB.

Do I just leave a pad empty?
If so, which one?

Any advice would be greatly received. Thanks!

[Thewintersoldier]

The vtl5c/2 has an led and an ledr with 2 legs. the 2 legs are a regular ledr. The vtl5c/3 has an ledr with 3 legs. this is essential 2 ledrs in in photocell. the center leg is shared by the two outer legs. you can simulate this by using 2 ledrs with one led and connecting one leg from each ledr and using those as the center leg.
      I have seen inside a vintage vactrol and they use a red 3mm led. closest I could get to the response of a vintage perkins elmer vactrol is the 9203 ledrs but it still didn't have the same response, and the exvive reissues don't sound the same in this circuit. I've built the sawse with a legit vactrol, it's good but not great.

[jimilee]

Just looking at the board, it looks like one of the outside pads doesn't connect to anything, so you would be able to use just a single LDR.


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[Guybrush]

Thanks both for the replies. Looking around the different forums it seems that 440 clones (be it the Mirror Ball, Sawse or  EF440 from General Guitar Gadgets) have a very hit and miss success rate.

I've just put my Mirror Ball together using the vtl5c/3 I have and whilst it 'works', there's definitely something not right. The envelope just doesn't respond in the way it should, it's really wobbly and unstable sounding. I'm also getting some background fizzy distortion when using the neck pickup.

I'll give the LED/LDR combo a try as per your message above Jimi but I won't hold my breath for a better result. Fingers crossed though!

Thanks again.

[jimilee]

It's not a fabulous pedal, but it's alright. It does sound like you have a few bugs to iron out.

[Thewintersoldier]

I'm not trying to be argumentative but I'm really failing to see where in the schematic it shows one leg of the vactrol not connected to anything. It would not work correctly with the ledr like the vactrol you used. I'm pretty sure if it could be done with a 2 leg ledr then every single diy layout would do so. Good luck getting it sorted out. But Jimi is right, there are better filters out there.

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[jimilee]

I'm not trying to be argumentative but I'm really failing to see where in the schematic it shows one leg of the vactrol not connected to anything. It would not work correctly with the ledr like the vactrol you used. I'm pretty sure if it could be done with a 2 leg ledr then every single diy layout would do so. Good luck getting it sorted out. But Jimi is right, there are better filters out there.

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No worries. I was looking at the board, I may have stayed schematic, my apologies.

The GGG schematic above has a 5C4/2 which doesn't have the third leg.


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[Thewintersoldier]

The sawse like the ggg schematic above uses the vtl5c/4 which has the third leg. The 5c4 has two and is the single ldr inside. I may be wrong but I'm pretty sure the /2 designation at the end is for dual ldr and hence the third leg. The sawse, ppcb and ggg board all have the third leg hole.

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[Guybrush]

Thanks guys. The similarly named vactrols, their reissues and differing layouts of the circuit certainly make it a bit confusing.

What other filters would you recommend Thewintersoldier?

I like the 440 as it's (seemingly) simple and has a low parts count.  And because it's the one Jonny Greenwood used on Paranoid Android. 

[jimilee]

The sawse like the ggg schematic above uses the vtl5c/4 which has the third leg. The 5c4 has two and is the single ldr inside. I may be wrong but I'm pretty sure the /2 designation at the end is for dual ldr and hence the third leg. The sawse, ppcb and ggg board all have the third leg hole.

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Weird, I looked it up to make sure I knew what I was talking about and still got it wrong.  I can say I've seen it before, like in the BYOC opticomp, that the third leg doesn't do anything. I have also used two LDRs and soldered the two legs together in the middle pad, on more than one build. I guess I need to dig mine out and see what the hell I did. I ran across it over the weekend while looking for something, I just gotta remember what box it's in.


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[Thewintersoldier]

the mutron III is still the king, the vfe mini mu replaced that, or the madbean flunkee which is a dod fx25 that is low parts and 13700 ota based. Pedalpcb has a board for the reissue dod 440 that is also 13700 based and sounds better than the original vactrol version.