CDXL Response

benny_profane

Well-known member
My CDXL build (corrected board) is having a number of issues.
  1. With ‘Level’ maxed out, I get my clean signal with a fizz mixed in, but no autowah.
  2. The response is sometimes extremely slow, and only kicks it on the decay of the note. This happens at various points of the sweeps.
  3. The wah doesn’t fall smoothly. It peters out in a very wobbly (think super fast phaser) way.
  4. Overall, it’s very weak (when it’s catching the input signal). Not at all as extreme as a wah sweep should be.
I used the Xvive VTL5C4/2 from SBE. I’ve tried various values at R9 (i.e., 2k2, 4k7, and 6k8). 4k7 seemed to get the closest. I’ve also tried various dual op amps (i.e., TL07, TL062, and TL022). The TL072 has the worst response.

I’ve tested the circuit both with and without a buffer before it.

I’m wondering if others have had good luck with the Xvive reissues or not. I know there’s one successful build report, but that’s it. In any case, any ideas?
 
OK, but this does not describe the distortion that Benny is experiencing and Benny's test data shows that his opto spans the entire resistance range. Benny's data is static and doesn't tell us anything about time response, so it's possible that the problem lies there. 3rd-hand info gives me a headache. I'm not inclined to pursue that particular line of inquiry.

You can try swapping out the opto. I suspect that if you had one, you'd have tried that already.

I don't like to advocate giving up, but in this case it might be more expedient to build one of the other auto-wah pedals on this site.
 
No one is disputing that an original could solve the issue. Me and a few others in this thread have been trying to work through this problem with current production parts. If that’s not possible—which it seems like it is since we’re running out of ideas—the project may not be viable.

I’m not keen on the idea of giving up on a circuit, but I’m out of ideas and rather out of my area of knowledge trying to push forward. Perhaps if we break down the circuit into functional blocks, we could come to something.
 
Looks like I might have to buy one of these boards. I remembered I bought a 440 kit from GGG a decade or so ago (one of my first builds...it didn’t work). One genuine vactrol still attached!
9A6D42C6-3061-4A17-BBBD-AB7CBEE6AC86.jpeg
 
Here's another link, Located in Florida, Scroll to Bottom of page :

Update : I just got a Quote of $85.00 each for a lot of 10, You read it right $850.00 for 10 only.
 
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I’m not keen on the idea of giving up on a circuit, but I’m out of ideas and rather out of my area of knowledge trying to push forward. Perhaps if we break down the circuit into functional blocks, we could come to something.

Maybe try 2 A500k external pots as Trimmers in place of the 220k resistors, Set pots to 220k before connecting to PCB :
CDXL External Trimmers.jpg
 
I’m not keen on the idea of giving up on a circuit, but I’m out of ideas and rather out of my area of knowledge trying to push forward. Perhaps if we break down the circuit into functional blocks, we could come to something.

Maybe try 2 A500k external pots as Trimmers in place of the 220k resistors, Set pots to 220k before connecting to PCB :
View attachment 2814
I appreciate the time you took to make that graphic. However, I’m wondering if that’s part of this issue at all here? If we’re thinking this comes down to the response time of the vactrol, will adjusting these values significantly alter the response?
 
Here's another link, Located in Florida, Scroll to Bottom of page :

Update : I just got a Quote of $85.00 each for a lot of 10, You read it right $850.00 for 10 only.
Who do they think will buy that?
 
I appreciate the time you took to make that graphic. However, I’m wondering if that’s part of this issue at all here? If we’re thinking this comes down to the response time of the vactrol, will adjusting these values significantly alter the response?
At the moment it's a Boat Anchor, what have you got to lose?

Other Option Below
Have you tried this Link :

or email Sales@Sierraic.com
 
Here's another link, Located in Florida, Scroll to Bottom of page :

Update : I just got a Quote of $85.00 each for a lot of 10, You read it right $850.00 for 10 only.
Latest : Came back with a new Quote of $25.00 each for 10 Only.
 
Got a Quote for 12 only @ $20.00 USD each, this does not include Shipping for Genuine NOS PerkinElmer VTL5C4/2.
Who would like to purchase, these will work!

Update : A Builder in the USA is looking into it & will report back with his Results!
 
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