Friday, June 14, 2013

Build a Wah Effect In Your DAW - with Audio Examples

The wah-wah pedal is one of the classics of the guitar world. With a few subtle (or no-so-subtle) moves of the foot a player can add a world of expression that's not possible with any other method. But what's actually going on inside that pedal. If you want the exact particulars this isn't the post. Those posts have been done to death and if you want to know how to track down that certain Dunlop from that certain era with that certain component in it that makes it magic, you can Google that like everyone else.

We're going to very briefly get into what makes a wah pedal tick and then show how you can create that same effect using just the tools you already have in your DAW. Then you can take it to the next level by adding automation.

A wah pedal is quite simply just a sweep mid EQ. The boost is fixed and generally pretty high, like +12 dB or even more. The width of the filter is somewhat less than an octave. The range of sweep runs from about 400 Hz to as high as 2.5 kHz. These vary by manufacturer and even within the same model over manufacturing runs. But the specifics aren't important. If you're trying to exactly recreate the sound of a particular wah then there's ways of going about that. By the time you take all the readings and set it all up you may as well just spring for a decent emulator or just buy the thing outright. What we're going to do here is just take the basic principle and expand on it for what is hopefully a new and unique sound.

To start, I grabbed a guitar track from a live performance I had recorded. Then I picked out a parametric EQ in Reaper. The picture below shows the first filter I set up and the lowest and highest center frequencies of a traditional wah pedal. In the audio example I'm just using one, the second one is only there for illustration but imagine how crazy you could make things by sweeping two filters at once!

Now that we know what we're working with, it's easy to get a little automation involved. You can either play the track back and modulate it in real time, recording your moves, or you can simply draw it in as you see fit. Going a step further, you can easily create an auto wah, or envelope follower effect by driving the frequency with the volume of the track. That is, the louder it gets, the more the frequency shifts. It can be very expressive.
The thing I like best about doing it this way in a DAW is that you have absolute control over all the parameters of the filter, not just the frequency. You can use less gain and a wider filter, like number two in the next picture, or have a super tight filter like number three. You can even use negative gain like number four. What's more, is that all those parameters are able to be automated as well. You can create an effect where the filter gets wider as the frequency increases, or the gain decreases as the frequency increases. There's really no limit. If you can figure out the automation, you can do it. You could even side chain input from another channel so that a vocal could control one or all of the parameters. Peter Frampton eat your heart out!
So with no further ado, let's get into the listening portion of this exercise and see what you can actually do with this knowledge. I spent just a very few minutes setting this up and I barely scratched the surface. Now that you're in the know, Brethren of the Knob and Fader, let's see how you can make that baby cry!


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