The Vanishing Baby

MarcoMike · September 24, 2007, 08:55:34 AM

First of all, the title explained: is it possible to mdulate a wah by the Vanishing Point?

Ok, here it is... Yesterday I found out that you can actually make a crybaby work by connecting avariable resistor to lug 2(wiper) and 3(ground) (or 1 and 3, it gives more or less the same result) of the hot-pot of a crybaby, while the treadle is full-back (bassy sound)

ok, if it is not so clear, here is a schem:

it seems 5k is the right one to get a full sweep, if the treadle is kept on its back position. the number of lugs required is now only 2 so that Andrews' Vanishing point is suitable to operate as an external variable (varying) resistor. will a vtl5c3 be able to work nicely in the 0-5k region?

I posted this before testing it, because at present I don't have any 4017 and I should be writing my thesis instead of DIYing...

anyway.... any comment is appreciated. will it work?

~arph · September 24, 2007, 11:08:38 AM

Yes it will work, depending how low the output resistance of the optocoupler can go.. (check the specs, they hardly ever go to 0 ohms). Probably the max resistance will be higher than 5k, but this can easily be limited with a 10k parallel over the optocoupler's output, or by making sure the input level of the optocoupler doesn't drop below a certain value so the output resistance doesn't get higher than 5k.

Michael Allen · September 26, 2007, 02:53:03 PM

http://www.diystompboxes.com/smfforum/index.php?topic=27090.20
http://www.diystompboxes.com/smfforum/index.php?topic=28396.0

I made one with a Morely power wah. You use the sequencer to change the LED brightness which you couple to a photoresistor that controls the wah frequency. Works incredibly well.

Search around for it, because it's been discussed many times here.

MarcoMike · September 27, 2007, 05:57:41 AM

Well, this is a great idea! I'm gonna try it on my ProPhaser.... and you don't even need the optocoupler, you can just put 8 LEDs together inside the Morley pointing at the photoresistors!

thank you Michael

~arph · September 27, 2007, 06:00:23 AM

eight diodes and one LED might fit better

MarcoMike · September 27, 2007, 07:28:46 AM

mh... $:-\$

true, I should better have a coffee now, and try to wake up!

sshrugg · September 27, 2007, 11:24:06 PM

Oooh. This looks really neat.

DWBH · September 28, 2007, 09:22:40 AM

I can't see nothing :S

sshrugg · September 28, 2007, 05:56:34 PM

Oh. Yeah. I see no pictures either. I was referring to the project ideas in those links.

MarcoMike · September 29, 2007, 03:15:32 AM

Well, it was only a GCB95 circuit with an external 5K variable resistor connecting from wiper to ground of the hot pot

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The Vanishing Baby