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Vintage threads from the first ten years

Voltage controlled wahs - Hey Mark - you out there?

8/25/1999 3:20 PM
R.G.	Voltage controlled wahs - Hey Mark - you out there? Now that I understand a bit more about how the inductor-wah works, it's clear that we can make this puppy jump through hoops. Simulation says that a dual opamp, inductor and JFET would make for a voltage controlled inductor based wah, and possibly voltage control on the existing transistor style wah. Everyone, but especially Mark, who I know thinks about things like this, what would be some interesting things to do with a controllable wah? I've come up with some potentials: - auto wah, of course, but based on the inductor type, not state variable or multiple feedback; includes multiple staggered wahs envelope controlled - LFO Driven wah(s) driven in sync, opposition, quadrature, or by random voltages - combinations with other effects that would add to the usefulness

8/25/1999 3:20 PM

R.G.

Voltage controlled wahs - Hey Mark - you out there?

Now that I understand a bit more about how the inductor-wah works, it's clear that we can make this puppy jump through hoops. Simulation says that a dual opamp, inductor and JFET would make for a voltage controlled inductor based wah, and possibly voltage control on the existing transistor style wah.

Everyone, but especially Mark, who I know thinks about things like this, what would be some interesting things to do with a controllable wah? I've come up with some potentials:

- auto wah, of course, but based on the inductor type, not state variable or multiple feedback; includes multiple staggered wahs envelope controlled

- LFO Driven wah(s) driven in sync, opposition, quadrature, or by random voltages

- combinations with other effects that would add to the usefulness

8/25/1999 6:06 PM
CJ Landry	The Mutron Vol/Wah has this very same circuit that you mention. If you do not know already, the wah is varied by the user sweeping the pedal through an opto devices light path. So, if one were to use an LFO to vary the light path you could vary the wah. Or better yet, replace the opto device with an inductor circuit arrangement you might get close to this idea. Or at least get a starting point. I have the schematic for the Mutron Vol/Wah and I will try to bring it to work to scan a copy and put it on my web page. CJ

8/25/1999 6:06 PM

CJ Landry

The Mutron Vol/Wah has this very same circuit that you mention. If you do not know already, the wah is varied by the user sweeping the pedal through an opto devices light path. So, if one were to use an LFO to vary the light path you could vary the wah. Or better yet, replace the opto device with an inductor circuit arrangement you might get close to this idea. Or at least get a starting point. I have the schematic for the Mutron Vol/Wah and I will try to bring it to work to scan a copy and put it on my web page.

CJ

9/24/1999 10:44 AM
Paul Hemshall	I suggest you look at Gyrators. Gyrators (negative impedance convertors), act as a real time physical model of an inductor using an op-amp 4 resistors and a capacitor. See the Art Of Electronics by Horowitz and Hill.

9/24/1999 11:27 AM
GFR	A single opamp will only be able to simulate inductors to GROUND. To simulate a floating inductor you need some more opamps. By the way, OTA's are easy to use in voltage controlled gyrators...

9/24/1999 2:31 PM
Paul Hemshall	Yeah I've got to admit to not investigating gyrators to much in the past, lack of time really. They did look promising when I first read about them. Theres something about being able to tune an inductor 'on the fly' that appeals to me.

8/25/1999 6:48 PM
Mark Hammer	You rang, sir? What can ya do with a controllable bandpass filter? How about a "rebound" wah that reverts to the initial control voltage: make it go "wah" and it answers with an "ow", make it go "ow" and it answers with a "wah". Kind of like a marriage between an autowah and a standard foot-operated unit; you tell it where to go then it automatically misbehaves. You'd need some kind of sample/hold feature to keep the initial position in a kind of analog memory for comparator purposes. While we're talking about sample and hold, my little Korg Pandora has a nifty little patch called "aqua" which is essentially a mediocre attempt to get a sample/hold filter sound. How about a random CV driven filter whose general range is set by footpedal position? (i.e., median frequency). The sound would be tantamount to singing through the straw in your soda pop, while somebody else mikes it and runs it through a Heil Talk Box. Fun enough? A dual wah/anti-wah that tracks well is another possibility. Given the lack of a decent source of good dual ganged pots for double wah purposes, any kind of voltage-controlled unit would permit a single decent reliable pot to control more than one wah module. CV inversion would get you "anti-wah" functions (one goes up while the other goes down), and CV mixing would let you easily stagger two modules to complement the desired tone or get special effects (e.g., simulate a phaser). Okay, last one then I go back to work. CV-controlled filters can be used with trigger delays to stagger the sweep in time. Wouldn't an octave down box sound amazing if the octave below and above were both autowahed a little out of sync? We're talking mucho thickness here; something that should come with a medical warning for those whose past includes a bit too much recreational pharmaceutical use. Bootsy, your pedal is calling! While I'm thinking of this, anyone out there ever play with an EH Queen Triggered Wah? An old ad I saw recently (hope you liked the memorabilia, RG) got me thinking about it. This puppy had all sorts of quirks, bells, and whistles.

8/25/1999 6:48 PM

Mark Hammer

You rang, sir?

What can ya do with a controllable bandpass filter?

How about a "rebound" wah that reverts to the initial control voltage: make it go "wah" and it answers with an "ow", make it go "ow" and it answers with a "wah". Kind of like a marriage between an autowah and a standard foot-operated unit; you tell it where to go then it automatically misbehaves. You'd need some kind of sample/hold feature to keep the initial position in a kind of analog memory for comparator purposes.

While we're talking about sample and hold, my little Korg Pandora has a nifty little patch called "aqua" which is essentially a mediocre attempt to get a sample/hold filter sound. How about a random CV driven filter whose general range is set by footpedal position? (i.e., median frequency). The sound would be tantamount to singing through the straw in your soda pop, while somebody else mikes it and runs it through a Heil Talk Box. Fun enough?

A dual wah/anti-wah that tracks well is another possibility. Given the lack of a decent source of good dual ganged pots for double wah purposes, any kind of voltage-controlled unit would permit a single decent reliable pot to control more than one wah module. CV inversion would get you "anti-wah" functions (one goes up while the other goes down), and CV mixing would let you easily stagger two modules to complement the desired tone or get special effects (e.g., simulate a phaser).

Okay, last one then I go back to work. CV-controlled filters can be used with trigger delays to stagger the sweep in time. Wouldn't an octave down box sound amazing if the octave below and above were both autowahed a little out of sync? We're talking mucho thickness here; something that should come with a medical warning for those whose past includes a bit too much recreational pharmaceutical use. Bootsy, your pedal is calling!

While I'm thinking of this, anyone out there ever play with an EH Queen Triggered Wah? An old ad I saw recently (hope you liked the memorabilia, RG) got me thinking about it. This puppy had all sorts of quirks, bells, and whistles.

8/25/1999 7:01 PM
R.G.	Hah! I knew I could count on you!

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