Interesting idea? (auto wah)

[vendettav]

hey guys i was reading thru some opamp stuff and then lfos and i thought is it possible to make an oscillator that'll respond to your guitar's volume pot and hook it to the wah wah thingy thru LED/LDR configuration
think of it as a fixed wah with your guitars volume pot. i guess you'd need a divider first, then drive it into an oscillating distortion or something, then hook it to an LED (how would you do this part?) and also have the other signal go thru the wah schematic leaving it clean... hmm i can see some problems with distortion pedals before this thing but it might work who knows.


so you think this thing is doable?

[anchovie]

so you think this thing is doable?

Can you describe in a clearer way what it is supposed to do? What do you want the wah to do as the guitar's volume changes?

[EATyourGuitar]

I have made things that oscillate that follow the guitar tone knob but its a really complicated circuit that involves a feedback looper and 3 other pedals in the loop. doesnt work on every guitar either. since every guitar has different output impedance and different size caps for tone. one thing thats probably never been done before is a pedal that takes impedance or capacitance measurements from the guitar during periods of silence. like a 5hz sampling rate maybe. that would be sick but it might require a pic microcontroller or ardruino. ya know I think I just invented something right there and you helped. this could be something really interesting if anyone put the extensive R&D time in.

[vendettav]

well pretty much what i meant is to have something that sounds like Fuzz Factory (not necessarily, something easy as that dead easy drive or something with lm386 would do) oscillating. you have different settings for the oscillation... so imagine while that pedal oscillates, the output doesnt go to the amp or whatever but drives an LED. and that's it. you don't hear it. However you also take a clean signal from your guitar and feed it thru this Wah circuit that has got a LDR being fed from the above mentioned LED. It'll act like a fixed wah wah. but if you turn your guitars volume down it changes the socillation frequency thus changing the Wah's position?

[ORK]

So it changes the wah position while becoming silent?

[Jazznoise]

This could be done much more easily with an expression pedal. This would seem to me like a wah pedal, though, unless you're trying to vary something other than the filter cutoff!

[anchovie]

This could be done much more easily with an expression pedal. This would seem to me like a wah pedal, though, unless you're trying to vary something other than the filter cutoff!

+1

And relying on a self-oscillating fuzz to control something won't produce very reliable results. I'm not sure it'll do much at all, in fact, other than make the LED appear on all the time. The drastic change in brightness with frequency that you're hoping for simply won't happen.

[vendettav]

hmm well i was thinking of having an LED to react on what the guitar sounds like. so when youve got oscillation it's stuck at one position, but playing some notes may open it up a bit. then when you turn your volume down, the frequency of the oscillation changes so does the LED's brightness changing the wah's position...

[anchovie]

the frequency of the oscillation changes so does the LED's brightness changing the wah's position...

Even if this worked (which I doubt) it would be useless. All the self-oscillating fuzz circuits that I've heard emit the oscillator tone when you play nothing on the guitar. Seeing as your idea included splitting the signal so that the wah affected a clean sound, the "fixed wah" effect would theoretically occur when there is no clean sound to be heard.

If you want a wah that reacts to playing, build an envelope filter and be done with it. If you want it to react to pitch, you'll need a fundamental extractor followed by a frequency-to-voltage converter.

[vendettav]

hmm well my fuzz factory clone does oscillate while i dont play. but never mind then

anyways if i get it correctly a simple LED/LDR kind of auto wah would be an envelope follower (or what are these called?) that would feed the guitar dynamic into an LED, a wah schematic with an LDR. and i'd need to make to make the LDR react on brightness vise versa? also may be a buffer in the beginning?
can any one hint me on an envelope follower or something?

[Jazznoise]

Hmm, still not really understanding what you want. Do you want an envelope follower to vary the filter? An lfo? An lfo that is retriggered by an envelope follower or something entirely different?

If you're looking for a good envelope follower filter I'd point you towards the Nurse Quacky, alot of people seem to enjoy it. It's on my (10 mile high) list of things to do. For the retriggering LFO I'd have a gander at this schematic which has an lfo that is triggered by the attack, but you'll need to chop out the VCO and use the Line In point as the beginning of your circuit. http://www.korg-datastorage.jp/Manual/monotron_sch.pdf

I know I've mention it twice in 2 posts now but this filter is beatifully aggressive though a tad dangerous - if I end up rehousing this as a stomp box (And I might) I'm going to have to limit the output!

[vendettav]

hmm i dont seem to have a LM358, can i use LM833 for Nurse Quacky??

[Jazznoise]

I can't say, your best bet is to put in a socket so that if it doesn't work you can swap it out for another op amp later!

[vendettav]

well yeah, i use sockets all the time with IC and Trannies