Quick help making my magnatone magnavibe vibrato more intense.

[aeiou]

This should be easy -- i have this pedal built up and working, but what should i change here to get a more intense vibrato? I'm looking for a deep, cutting, almost sea-sick vibe.. Thanks all.

[nocentelli]

What have you got for the optocoupler portion? A diy LDR/LED or a proper vactrol?

[aeiou]

it's an ldr/led.

[artifus]

what kind of led and have you measured your ldr? ie, is it an 'ultral bright' led and what range does your ldr cover? its usually a few k to a few m over a few seconds from light to dark.

*edit* i think knowing your ldr is key here, with reference to the circuit it is being implemented in. it's a light dependant resistor. think about that. think about light. what is the ldr's resistance when in complete darkness? what is its resistance in bright light? what affect does this resistance have on my circuit? how long does it take to get from one resistant extreme to the other? how bright is my led at 'full' brightness? does it ever get there? how far away from my ldr is my led? what effect does this distance have on my ldr's resistance? can i filter the light? etc

[nocentelli]

Distance is the key: They need to be close, but closest (i.e. touching) is not neccessarily deepest, they should be a few mm apart. 

[R.G.]

This should be easy -- i have this pedal built up and working, but what should i change here to get a more intense vibrato? I'm looking for a deep, cutting, almost sea-sick vibe..

That is one stage of phase shift. It will produce limited results. If you want more, you'll need to stack more stages. This stage is very similar to the phase shift stage in the Univibe. You may want to read "The Technology of the Univibe" at geofex for some insight on that.

The simple way is to tack on a number of additional phase shift stages. Four to eight stages instead of one will get a more intense vibrato. You may also need to distribute the phase capacitor value to get vibrato evenly at bass, mid and treble; or to concentrate it for a more shifty effect.

[aeiou]

In response to everyone concerning LDR and LED distribution -

I've played around with brightness and distance and think I've eked out all I can regarding light performance [in this particular build]

In response to R.G. -

Thanks for the info. I'll experiment with adding on some more stages shortly -- Still I wonder -- Is there anyway to modify this [single stage] circuit to get a bit more OOMPH as it is?

[R.G.]

In response to everyone concerning LDR and LED distribution -
I've played around with brightness and distance and think I've eked out all I can regarding light performance [in this particular build]

In response to R.G. -
Thanks for the info. I'll experiment with adding on some more stages shortly -- Still I wonder -- Is there anyway to modify this [single stage] circuit to get a bit more OOMPH as it is?

The engineering approach is to try to isolate what makes the changes and see how far you can push the changes.

In this case, I'd remove the LED/LDR entirely and sub in a pot. Something like maybe 1M linear. The LED/LDR amounts to a scheme to make the resistance of the LDR vary. So put in a pot and vary it by hand to see how far you can push it. So isolate things. Rip out the LDR and assume that some kind of LED/LDR will make the LDR vary between 0 ohms and 1M.  Or 5M. Or 10M. Most LDRs go to 1M or less, few to over 10M. And the higher they go, the less they can go low, say, below 1K. A pot can do that nicely. Then fire it up, and twist that pot, which is what the LED/LFO does to the LDR. Or have a lovely and talented assistant twist the pot while you play.

That will tell you the limits of what the basic circuit can do if you get the LED/LDR perfect. If you're not happy with those limit, no amount of tinkering with the LED/LDR will help. If it gets you where you want to go, super. Now you KNOW that all you have to do is tinker the LED/LDR.

And you do have to do what I'm always harping on. What, exactly, do you mean by "OOMPH"?

I realize that I view all things through the prism of thinking that a single transistor circuit is so simple that it's like another grain of rice in the bowl, but that's not necessarily how other people see it. It's a failing I try to keep in check.