The Thing (Dynamorph from DeadEndFX) LEDs are always lit (and not in a good way.)

[xefned]

I very carefully built "The Thing" from DeadEndFX, and the moment I plug in 9v, the LEDs light up. They're supposed to pulse with the guitar attack—adjustable with the trimpot. And they do at certain settings, but they never go fully dim.

The 3 on the left are brighter than the 3 on the right. That might be normal since they're 2 pair of LEDs in series (not parallel.)





The only fucky thing I did is sub the 2k rate pot with a 5k pot w/ 3k3 resistor on the outside lugs.
The rate pot seems to have no effect. So perhaps that resistor trick doesn't work in this configuration.





The drag part is turning the full 25 rotation trimpot, I never reach the 6.2v specified. I can adjust only from 4.38vDC to 5.37vDC



I'll replace the rate pot (currently 5k +3k3Ω resistor) with a proper 2k pot but I'm not sure it'll make any difference. As is, the rate pot does f**k-all. So I might as well try.

If anyone has any thoughts or suggestions, then thank you. Otherwise this is just a report from the field.

 

[pcborpcp]

Right now it's packed away in my box of things I never want to look at again. But I will dig it out and measure next week.

FYI: the vactrol LED is only working when the pads (3 + 4) for the expression jack are connected. So your opto probably has not been working correctly at all

 

[xefned]

FYI: the vactrol LED is only working when the pads (3 + 4) for the expression jack are connected. So your opto probably has not been working correctly at all

It's interesting that I *just caught that* when I posted the snippet of the schematic. Dang! Should've bridged those pads before I determined the envelope wasn't working.

I did eventually add the expression jack. But I might have already dorked the R60 before this stage, I can't remember.

Yet another reason this forum rules.

 

[pcborpcp]

It's interesting that I *just caught that* when I posted the snippet of the schematic. Dang! Should've bridged those pads before I determined the envelope wasn't working.

I did eventually add the expression jack. But I might have already dorked the R60 before this stage, I can't remember.

Yet another reason this forum rules.

Awesome, I hope you'll give it another shot!
I went with a NSL-32SR3 that I still had around. Sounds better to me than the VTL5C1, but I might test a VTL5C9 when I'll get some. I still have to play a bit around with the trimpot to find the sweet spot of the threshold sensitivity edge, but so far so good

 

[pcborpcp]

Awesome, I hope you'll give it another shot!
I went with a NSL-32SR3 that I still had around. Sounds better to me than the VTL5C1, but I might test a VTL5C9 when I'll get some. I still have to play a bit around with the trimpot to find the sweet spot of the threshold sensitivity edge, but so far so good

Alright, I think I got it up and running. Had to dial the trimmer up to 6.40v to stop the oscillation and now the threshold works more as I imagined. Kinda odd that they were so specific in the build doc about setting the voltage between 6.18-6.20v... Anyways, I have to spend more time with it, but so far I think the thing sounds really cool.

 

[xefned]

Alright, I think I got it up and running. Had to dial the trimmer up to 6.40v to stop the oscillation and now the threshold works more as I imagined. Kinda odd that they were so specific in the build doc about setting the voltage between 6.18-6.20v... Anyways, I have to spend more time with it, but so far I think the thing sounds really cool.

I'm so happy to hear that.
I will dig back into it this weekend. Thanks for the encouragement!

 

[pcborpcp]

I'm so happy to hear that.
I will dig back into it this weekend. Thanks for the encouragement!

That's great!
I like the pedal a lot! But I like the projects that needed some troubleshooting always more than the ones that go smoothly, lol.
Just keep in mind that the "vactrol's main purpose is to adjust the drive level according to the picking dynamics (pick attack)" (from the build doc). The pedal is a bit tricky when it comes to gain staging - if the LED's won't dim, you might come in too hot. My LED's were always bright because of the oscillation, but now they seem to behave as intended (the harder the attack, the brighter the LED's will get).
I hope you'll be able to fix your issue. But I think you just have to add the right resistor for your vactrol, now that you have the expression jack installed. I know others were a bit dismissive, calling it "just" a Prunes and Custard variation, but I see it more as a different take/interpretation of that circuit. I will definitely build a P&C clone to compare it to the Dynamorph. But as it stands, I'm happy that I could build such an obscure pedal (thanks to DEFx) and the process was really fun.

 

[pcborpcp]

I'm so happy to hear that.
I will dig back into it this weekend. Thanks for the encouragement!

Have you found the time to work on your pedal?

 

[xefned]

Have you found the time to work on your pedal?

Oh man, thanks for the encouragement. I can't even remember where I left off.

I opened it and found I'd socketed the infamous DNL resistor. It was loaded with a 4M7 but I found all values did nothing.

Finally put a 470Ω in R60 and recalibrated to no avail.
I must've just built the thing wrong. I could try a real NSLR3, but it's good like it is as a "prunes &C" style foldover drive.

It still sounds great without the envelope. You wanna play the lead line to Can't Get No Satisfaction whenever it's plugged in.

 

[eh là bas ma]

If you have some trouble with a DEFX build, i'd humbly suggest to post your issue also at diystompboxes.com.

Building your own stompbox

Post your questions about building your own stompboxes.

www.diystompboxes.com

Digi2t from DEFX is an active member there, so soon or later, he'll probably help you understand the issue and fix your build ?

Just make sure you write DEFX in the title, or he might miss it.