Like HowStuffWorks on Facebook!

How Guitar Pedals Work


Make It Sing: Filter, Modeling and Multi Effects

Changes in frequency, wavelength, wavenumber, amplitude, intensity, speed and direction will all affect the way we perceive sound waves. Filter effects work on those sound wave qualities in a number of ways. Wah-wah will make your guitar sing or cry. Tweaking EQ can make your signal as tinny as an old AM radio or as bass-heavy and muffled as the club next door. Here's the skinny on filter and modeling pedals:

  • Wah-wah pedals. Made famous by Jimi Hendrix and countless other musicians, Wah-wah pedals filter out certain frequencies and compress others. Rock the pedal up and down to change the frequency of your signal's resonant peak, creating a distinctive crying sound [source: Keen].
  • Envelope filter/auto-wah. Auto-wah pedals are wah-wah pedals you can set and forget. They work using an envelope filter to fold sound back in on itself. Stevie Wonder popularized one of the first (and still best-loved) envelope filters, the "Mu-Tron III."
  • EQ pedals. Straight equalizer (EQ) pedals allow a player to boost or lower frequencies within a variety of ranges. Multi-band graphic equalizers can compensate for a variety of signal problems or room-sound oddities in live situations. EQ pedals can also be used, sometimes in conjunction with an expression pedal, to simulate a variety of synthesizerlike filters. For instance, lower or remove high frequencies to get a muffled, "club-next-door" effect.
  • Modeling pedals. These use a variety of EQ filters to simulate the sounds of other things, often classic amplifiers. Boss makes an Acoustic Simulator pedal which enables electric guitarists to reasonably approximate acoustic guitar tones. Tech 21 produces a SansAmp pedal that will allow a guitarist to plug directly into a PA and sound like he or she is playing through an amplifier that has been tweaked in a number of ways, with options for tone, overdrive and other settings.

In addition to dynamic, modeling, time-based and filter effects, many pedal manufacturers have also developed all-in-one solutions. The Boss ME-70 Guitar Multiple Effects Pedal Board bundles a variety of different effects into a single powerhouse pedal. Line 6 makes a line of popular Pod effects that simulate classic amplifier sounds and also offer a variety of different effects.

Now that you know how effects pedals work, it's time to put them to use. We'll talk about developing a signature sound on the next page.