Xvive Vactrols from China BEWARE

[bushidov]

Here's the pot adjustments:

I was basing this on the schematic of GGG:
http://www.generalguitargadgets.com/effects-projects/filters-envelope/dod-440-ef/

I've discovered the Beavis Audio schematic appears to have errors. Different Vactrol type, for that matter.

If I pull the Vactrol out, all that extra noise goes away, so it doesn't appear to be a bad solder job or bad components otherwise. I did leave sockets for where the vactrol's 5 leads went so if I ever got another or figured out how to roll my own, I'd have something to compare it to.

[rankot]

Check C3/C4 capacitor values, as well as values of C2, R4, R5 and R6. Check if your D1 or D2 is soldered backwards, for example.

[bushidov]

So, no problems detected on values or orientations.

Check C3/C4 capacitor values

C3, the bias decoupler electrolytic capacitor, is 10uF and is soldered on with the proper polarities in mind.
C4, the op amp DC decoupler electrolytic capacitor, is 4.7uF and is soldered on with the proper polarities in mind.

as well as values of C2, R4, R5 and R6

C2, the input box film capacitor, is 10nF and its solder job has proper continuity.
R4 is a 10K resistor and is soldered into the correct position.
R5 and R6 are 100K resistors and are soldered into the correct position

Check if your D1 or D2 is soldered backwards

D1 and D2 are 1N4148 diodes and are soldered on with cathode and anode position in mind, correctly.

Keep in mind the Beavis Audio schematic is incorrect, primarily due to their vactrol. A 4 pin VTL5C9 wired that way cannot envelope filter (as pedalpcb found out the hard way when copying it and releasing their version of it). It requires a 5 pin style VTL5C4/2 (as pedalpcb later figured out and GGG already knew)

[rankot]

Regarding DOD440, there some info here: https://www.diystompboxes.com/smfforum/index.php?topic=98638.0, here https://www.diystompboxes.com/smfforum/index.php?topic=112323.0 or here http://guitar-fx-layouts.42897.x6.nabble.com/DOD-440-td3168.html

[bushidov]

Checked that. No go. I'll break this off into a new post.

[rankot]

Checked that. No go. I'll break this off into a new post.

OK. In case you decide to make your own vactrol, here is the datasheet for VTL5C4/2:



You need two matched LDRs for that. You may try with GL5516, for example, they seem to have similar characteristic to VTL5C4/2, but you also need to find a good LED for the purpose. Have in mind that different LED's produce different amount of light with the same current, so you must experiment to match datasheet specs. If you use those LDRs, pick green LED. But what can be the problem here is the fact that most of similar LDRs have fall time in 30-50ms range, while VTL5C4/2 has fall time of 1.5 seconds! Thus, you may need some more ripple filtering before LED, because such a slow fall time make unnecessary to filter envelope before the LED, and short fall times require that. Unfortunately, I'm not aware of LDRs with such a long fall times.

[bushidov]

Here is a hypothetical and possibly stupid question on my part: only for the sake of testing, could I rig a dual gang pot (Or regular pot) to emulate the vactrol? I mean, I can spin a pot back and forth within 1.5 seconds, if nothing more than to just test.

[rankot]

Of course you can. 

[duck_arse]

Here is a hypothetical and possibly stupid question on my part: only for the sake of testing, could I rig a dual gang pot (Or regular pot) to emulate the vactrol? I mean, I can spin a pot back and forth within 1.5 seconds, if nothing more than to just test.

if you have a pair of same type ldr's, you can tack solder them in as a dual, then just wave your hand over them, with a stong light above. you should hear some sweep. if you can lash it up on a breadboard and cover the ldr's and a led, you can get a better bit of sweep action. if you just want to test the rest of the circuit operation, that is.

[bushidov]

Thanks Duck_Arse and Rankot, I'll give it a try. I created a new post for this issue as to not be tacked onto the original poster's question.

[ficelles]

So to save others the self induced grief caused from being a tight wad you should avoid the following vactrols on Ebay;

https://www.ebay.ca/itm/5pcs-VTL5C3-Xvive-Audio-Opto-Coupler/392257148367?hash=item5b545915cf:g:Y0AAAOSwzMlchhaS

I bought one of these fake XVive vactrols, the fake measures 25M dark resistance where a VTL5C3 is 10M, I complained and got an instant refund no return needed so I took it apart and found a cheap red LED where a VTL5C3 has a standard green one. The fake one probably works ok for some applications but not typical audio. It actually worked better when I stuck a green LED but the resistance is still wrong if you need a VTL5C3...

[rankot]

I bought one of these fake XVive vactrols, the fake measures 25M dark resistance where a VTL5C3 is 10M, I complained and got an instant refund no return needed so I took it apart and found a cheap red LED where a VTL5C3 has a standard green one. The fake one probably works ok for some applications but not typical audio. It actually worked better when I stuck a green LED but the resistance is still wrong if you need a VTL5C3...

Dark resistance is not actually too important in most uses! What IS important is bright resistance, as well as rise and decay times. That is because in most times LDR is used in parallel with another resistor, so if it is not lit, another one takes precedance.

[ficelles]

Dark resistance is not actually too important in most uses! What IS important is bright resistance, as well as rise and decay times. That is because in most times LDR is used in parallel with another resistor, so if it is not lit, another one takes precedance.

Tricky to measure light resistance though, or is there an easy way to do it?

[soggybag]

I like the VTL5C9 which run about $9 ouch! I got some XVive substitutes from AliExpress for about $1 each. I bought 15 and tested one at random and it worked fine. By ear it seemed to have the same qualities as the VTL5C9.

I didn't test all of the 15. I did notice the quality wasn't quite as good. Some of the LEDs were loose in the enclosure. This shouldn't affect performance.

[PRR]

Tricky to measure light resistance though, or is there an easy way to do it?

Light. Ohm meter. What is tricky?

I find dark resistance trickier. Response extends to VERY DARK. Far too dark to read the meter. I've rigged baffles and remote meter. Fortunately I never need "true dark". In fact if it goes over 100k that's normally great.

[rankot]

I like the VTL5C9 which run about $9 ouch! I got some XVive substitutes from AliExpress for about $1 each. I bought 15 and tested one at random and it worked fine. By ear it seemed to have the same qualities as the VTL5C9.

I didn't test all of the 15. I did notice the quality wasn't quite as good. Some of the LEDs were loose in the enclosure. This shouldn't affect performance.

Care to share a link to those?

[soggybag]

Here is what I bought, cheaper than I remembered $3.70 for 5 plush shipping. I paid $16.41 for 15 shipped.

https://www.aliexpress.com/item/4000258174075.html?spm=a2g0s.9042311.0.0.30974c4dxj9IfC

[rankot]

Here is what I bought, cheaper than I remembered $3.70 for 5 plush shipping. I paid $16.41 for 15 shipped.

https://www.aliexpress.com/item/4000258174075.html?spm=a2g0s.9042311.0.0.30974c4dxj9IfC

I see, but shipping to my country is 90 USD... 

I have a few of similar marked optos, maybe they're the same? Will check.

In the meantime, there are datasheets for Xvive products: http://www.xviveaudio.com/art/download-a0044.html

[soggybag]

Here is what I bought, cheaper than I remembered $3.70 for 5 plush shipping. I paid $16.41 for 15 shipped.

https://www.aliexpress.com/item/4000258174075.html?spm=a2g0s.9042311.0.0.30974c4dxj9IfC

I see, but shipping to my country is 90 USD... 

I have a few of similar marked optos, maybe they're the same? Will check.

In the meantime, there are datasheets for Xvive products: http://www.xviveaudio.com/art/download-a0044.html

I'm not sure where you're seeing $90 shipping. I paid $16 for 3 packs of 5. When I tap shipping I see AliExpress shipping $3.05, EMS $40.17 and DHL $40.28. I obviously chose the first option. There's no way I'd pay $40 shipping for $10 of parts.

[rankot]

Here is what I bought, cheaper than I remembered $3.70 for 5 plush shipping. I paid $16.41 for 15 shipped.

https://www.aliexpress.com/item/4000258174075.html?spm=a2g0s.9042311.0.0.30974c4dxj9IfC

I see, but shipping to my country is 90 USD... 

I have a few of similar marked optos, maybe they're the same? Will check.

In the meantime, there are datasheets for Xvive products: http://www.xviveaudio.com/art/download-a0044.html

I'm not sure where you're seeing $90 shipping. I paid $16 for 3 packs of 5. When I tap shipping I see AliExpress shipping $3.05, EMS $40.17 and DHL $40.28. I obviously chose the first option. There's no way I'd pay $40 shipping for $10 of parts.

For my country, there's only one option for shipping, DHL and it costs USD 90... Before this COVID outbreak, shipping was possible using regular post and was dirt cheap, but it seems there's no more now.