How does this Vibe Mod roughly work? (on Rick's Little Angel chorus)

[gcme93]

I've traced the paths from two schematics with the following results:

IvIark's Vero (Vibe version) http://tagboardeffects.blogspot.co.uk/2012/02/little-angel-chorus-rick-holt.html

Harald's Vero (Basis of my build) http://www.sabrotone.com/wp-content/uploads/2011/04/LittleAngelRev1.gif

This is from Pin 1 of the TL072 to the output:

The vibe circuit: (SPDT on = Vibe engaged)

pin 1 ---- 100nF ---- 10k ---- 100nF ----- Out
         \                                              /
          \----10k ---- 100nF --- SPDT--/


Non vibe

pin 1 ----- 10K ----- 100nF ----- Out


So it appears to be an almost identical impedance in parallel. Is this right? Is this some clever change in the output filter or something? I thought Vibe wasn't just a wider chorus but I'm probably wrong...

Any answers greatly appreciated!

[slacker]

I think you're looking at it wrong, what the vibe mod does is disconnect pin 1 from the output by removing the 10k resistor. In your non vibe drawing it removes the 10k. This means you only hear the delayed signal from the PT2399 as this is modulated it goes up and down in pitch giving the vibe sound.

I'm not sure how you've got two paths from pin 1 to the output in your vibe example, the second path goes to the input of the PT2399 not the output. It's probably clearer if you look at the schematic.

[gcme93]

I'm not sure how you've got two paths from pin 1 to the output in your vibe example, the second path goes to the input of the PT2399 not the output. It's probably clearer if you look at the schematic.

Here's my thinking: it seems to be one path or both?? Have I missed something obvious, because I agree, it makes more sense for it to disconnect entirely

[slacker]

Ah I see what you mean, it does look like two paths, I hadn't noticed the second one before. If you look really carefully though there's a trace cut under the 100k resistor 8 rows down, 7 from the right, check against the right hand image, so the second path doesn't go to the output.

[gcme93]

Ahaa! Very devious indeed. I knew it would be something like that but I couldn't spot it for the life of me. Thank you very much!

Now to add it into my multi effect build. I've already built Harald's layout and was very happy with it, so now I can add in the Vibe mod because I finally know what's going on (not so bothered about the crazy Space mod)!

Thank you very much Ian!