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Vintage threads from the first ten years

Re: 650 uH inductor?

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1/25/1998 10:12 PM

Re: 650 uH inductor?

As to inductorless wahs, there are a couple of standard opamp style circuits that do a wah type sound, although what you get will NOT have the sound of the classic inductor style wah, as the imperfections of the inductor will not be there. Same for gyrators, unless you use a pot full of circuitry to put the "imperfections" back in. The tube wah on LXH2's web page is a feedback style wah, cousin to the opamp ones.

I'll take this as a challenge my friend.

at least with you, I know it won't get me into any *legal* trouble. (double

)

If you can point me to these other 'standard' opamp style circuits that do the wah type sound, I would appreciate it. I've messed with different inductor characteristics and what effect they have on the response. (simulation wise that is). I think I understand a lot about what makes the difference in a wah pedal. (I *think* being the operative word). I am anxious to test what I think. I've read all the articles about the vox wah and the magical inductors. I think 'Q' has a lot to do with it but I would much rather try it and see.

--jg

1/27/1998 4:45 AM

paul francis perry

An inductorless filter type thing I have had luck with (though I am not a guitar person) is the LM13600 dual operational transconductance amplifier based one in the data sheets for this chip in the National Semiconductor data sheets
(which I suppose are online).
The voltage to current convertor given in Horowitz and Hill "The Art of Electronics" is just the ticket for driving this, though I noticed that I needed a 390 ohm resistor from the bottom of the voltage source pot to earth to stop the system locking off when the control voltage falls below 35mv.
Nice to have a resonance control!
In a 'real' wah I think the resonance might vary over the frequency sweep, but if youlike extreme effects ( I am an EH fan) this one is good, I have built a few!

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