CDXL Response

[benny_profane]

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?

 

[Chuck D. Bones]

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.

 

[music6000]

I believe that if you can find an Original VTL5C4/2, the issue would be solved :




Tone Factor 442

This uses a KA4558 Op Amp

 

[benny_profane]

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.

 

[Nostradoomus]

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!

 

[music6000]

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!
View attachment 2800

Ha Ha , Try reflowing some of those pads, You can almost see through them.
How much for that PRC vactrol ?

 

[music6000]

Here's another link, Located in Florida, Scroll to Bottom of page :

Distributor Of Electronic, Military, Obsolete & Passive Components.

We are your distributor & supplier for electronic, military and passive components, obsolete semiconductors, AMP connectors, integrated circuits, capacitors, transistors & other discontinued parts. Purchase Electronic, Military, Obsolete & Passive Components at summitelectronics.com.

www.summitelectronics.com

Update : I just got a Quote of $85.00 each for a lot of 10, You read it right $850.00 for 10 only.

 

[music6000]

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 :

 

[benny_profane]

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?

 

[benny_profane]

Here's another link, Located in Florida, Scroll to Bottom of page :

Distributor Of Electronic, Military, Obsolete & Passive Components.

We are your distributor & supplier for electronic, military and passive components, obsolete semiconductors, AMP connectors, integrated circuits, capacitors, transistors & other discontinued parts. Purchase Electronic, Military, Obsolete & Passive Components at summitelectronics.com.

www.summitelectronics.com

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?

 

[music6000]

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 :

VTL5C42 | PerkinElmer Optoelectronics Distributor |

Get the latest price and delivery info for VTL5C42 PerkinElmer Optoelectronics, Photoconductive Cells and Analog Optoisolators (Vactrols)

www.sierraic.com

or email [email protected]

 

[Chuck D. Bones]

Who do they think will buy that?

Government contractors buy stuff like that. It's cheaper to build an old design that do a redesign.

 

[music6000]

Here's another link, Located in Florida, Scroll to Bottom of page :

Distributor Of Electronic, Military, Obsolete & Passive Components.

We are your distributor & supplier for electronic, military and passive components, obsolete semiconductors, AMP connectors, integrated circuits, capacitors, transistors & other discontinued parts. Purchase Electronic, Military, Obsolete & Passive Components at summitelectronics.com.

www.summitelectronics.com

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.

 

[music6000]

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!

VTL5C42 | PerkinElmer Optoelectronics Distributor |

Get the latest price and delivery info for VTL5C42 PerkinElmer Optoelectronics, Photoconductive Cells and Analog Optoisolators (Vactrols)

www.sierraic.com

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

 

[Chuck D. Bones]

You're going on the assumption that these are the one and only problem. Guess we'll see.

 

[music6000]

You're going on the assumption that these are the one and only problem. Guess we'll see.

I have a Builder in the USA who is working on it & will report back when he has got the Parts & Build completed.

 

[benny_profane]

Bump to see if anyone has had success here? I’ve admittedly put it it pedal purgatory and haven’t worked on it further.

 

[Chuck D. Bones]

I found some real Vactech VTL5C/4 in my NOS stash. No clue where or when I acquired them. Must have been sometime in the previous century. When I get around to it, I'll breadboard this circuit and report my findings.

 

[benny_profane]

Awesome, looking forward to that.

And: Some?! I’d buy one off you if you’d be willing to sell.

 

[music6000]

Bump to see if anyone has had success here? I’ve admittedly put it it pedal purgatory and haven’t worked on it further.

Yes, I'm waiting on the Builder to Report back!!!

 

[Chuck D. Bones]

And: Some?! I’d buy one off you if you’d be willing to sell.

I've only got 4 of them, so I will not be selling any. Sorry.