Guitar EQ Pedals

These often overlooked pedals can solve problems and give added tonal versatility to your other pedals

By Phil O'Keefe

Recently on the Harmony Central Effects forum, someone asked why EQ pedals aren't more popular with guitarists. One person speculated that it is due to the presence of decent tone and EQ controls on many modern pedals; and while in some cases the quality of EQ controls on "dirt" pedals has increased in recent years, there are still many pedals that lack EQ entirely, or that could benefit from more EQ adjustment than the onboard tone controls provide. Modifying the sound of distortion pedals is just one area where a dedicated EQ pedal can be very useful. Let's have a look at some of the types of EQ that you may find in pedal form, and what sort of problems they can solve; as well as some creative purposes they can be used for.

WHAT IS EQ?

EQ, which is short for "equalization" was first used in the telecommunications industry to "equalize" the sound at all frequencies, and to compensate for high frequency signal loss over long telephone transmission lines. EQ uses filters and amplifiers that affect only portions of the audio frequency range, allowing the user to adjust the tonal balance of low, midrange and high frequencies in various ways. Eventually the audio and electric musical instrument industries adopted equalizers for similar corrective use, as well as for tone shaping purposes. With "creative" use, equalizers can take a sound and mangle the tone in all sorts of different ways, making it sound far different than it did to begin with.

TYPES OF EQ PEDALS

There are two basic types of EQ pedal that you're likely to encounter. The most common type is a "Graphic EQ" such as the Boss GE-7 and Danelectro Fish and Chips 7 Band EQ (Figure 1).

Figure 1: The Danelectro Fish & Chips 7 band graphic EQ pedal (click on images to enlarge).

A graphic EQ pedal usually has anywhere from six to ten EQ filters at different pre-set frequencies; each usually spaced one octave apart and controlled by a center-detented up / down slider. Pushing the slider up boosts or increases the level at that frequency, while moving it down "cuts" the sound at the indicated frequency. Each frequency band can be boosted or cut; typically by up to 15dB. The lowest frequency band is adjusted with the slider on the left, and highest on the right; the controls themselves visually form a "graphic" representation of the frequency range (from left to right, low to high) and show exactly what the EQ is doing to it. Typically a six band graphic EQ like the Maxon GE601 will have controls for the frequencies from 100Hz up to 3.2kHz, while a ten band unit like the MXR M-108 covers a wider range; from 31.25Hz up to 16kHz.

Although less common than graphic equalizers, the second type of EQ pedal you may run across is the Parametric EQ. A true parametric EQ has a minimum of three controls:

• Sweepable Frequency Select
• Boost / Cut
• Q (or Bandwidth)

The sweepable frequency control selects the center frequency of the EQ, while the boost / cut control adds or subtracts gain (volume level) at the selected frequency. The Q, or bandwidth control affects how much of the signal above or below that center frequency will also be affected by the boost or cut. This allows you to dial up anything from a narrow band "notch" filter (great for reducing 50/60Hz ground loop hum) all the way to a wide two octave bandwidth range, which would be better suited to overall tonal balancing, such as for cutting some bass overall, or adding in more sparkle and brightness in the treble region.

KIND OF, SORT OF

Despite how they're sometimes named, many "parametric" EQ pedals are more accurately called semi, quasi or pseudo parametric EQs; these pedals typically have the sweepable frequency select and cut / boost controls, but lack the flexibility that comes along with the bandwidth or "Q" control of a "true" parametric design.  Most, such as the Carl Martin 3-Band Parametric Preamp and the Catalinbread VariOBoost (Figure 2), have the bandwidth pre-set at a one or two octave range, which makes them useful for general tone adjustments, but less effective as a "problem solver", or for narrow bandwidth, "resonant filter" type EQ sound effects purposes.

Figure 2: The Catalinbread VariOboost is a 0-20dB boost pedal that also includes a two knob, one-band semi-parametric EQ.

WHERE IN THE CHAIN

First think about what you want to accomplish. Do you want to equalize the sound of the guitar that's feeding into the distortion pedal, or sculpt the sound that is coming out of it? EQ pedals can go practically anywhere in your pedal chain, but they will respond differently depending on where they are positioned relative to your other pedals. For example, if you place an EQ before a distortion pedal (Figure 3), you can control the frequencies that will be clipped. Anything you boost on the EQ pedal will receive more "grit" from the dirt pedal, and anything you cut will be less distorted. If you place an EQ after a distortion pedal (Figure 4), the EQ will act more as an overall tone control; affecting the balance of the sound overall, and having no real effect on the amount of clipping--only the relative frequency balance of the final sound. You can use this to your advantage. For example, the Electro-Harmonix Big Muff Pi is a well loved fuzz pedal with a huge low frequency response, but the midrange can be a little "soft"; an EQ pedal in front of it in the chain can be used to tame the bottom and bring the mids out a bit more so the guitar "cuts through" better onstage or in a mix. The Ibanez TS9 Tube Screamer oevrdrive has the opposite EQ sound - a boosted midrange "hump" and less in the low frequency range… try placing an EQ pedal after it in the chain and adding a bit of bass and pulling the mids back a touch to balance out the sound.

Here are a few more "pre / post dirt" EQ guidelines:

• Too much bass "going in" can lead to a flabby, muddy sounding low end. An EQ in front of the distortion pedal with the lows pulled back a bit will help with definition and clarity.

• Boosting a frequency pre-distortion tends to accentuate that frequency and causes more distortion in that band.

• If your distortion sounds too shrill, an EQ after the dirt pedal can be used to roll off some of the high frequencies and smooth out the sound.

• Adding low frequency EQ after distortion is usually a better way to get "fullness" than adding it in front of a dirt box. 

• Remember that these are just some suggested starting points. Ideally, you should experiment with placing your EQ pedal before and after any fuzz and overdrive pedals you use, and see which approach you prefer.

Figure 3: Use EQ before an overdrive, distortion or fuzz ("dirt") pedal to accentuate the frequencies you want to distort, and de-emphasize the ones you don't.

Figure 4: Use EQ after a "dirt" pedal to shape the overall sound. Adding bass after dirt usually works better than adding bass going into it.

OTHER NIFTY EQ USES AND TRICKS

• Wah pedals use a relatively narrow band resonant EQ filter that is swept in frequency when you rock the pedal back and forth. You can simulate the resonant sound of a "parked" wah by boosting heavily in a narrow frequency range with a graphic or parametric EQ. Cutting some of the frequencies above and below the boosted frequency range can make the effect even more dramatic.

• Since a wah is essentially a foot controlled, sweepable EQ filter, don't forget to try it before and after your dirt pedals. Fuzz pedals in particular can react very differently when placed in front of, or after a wah pedal.

• Using a parametric EQ, dial up a narrow "notch filter" at  60Hz and cut heavily to reduce ground loop hum.

• Does your semi-hollowbody guitar feed back at high volumes? Use an EQ pedal to lower the level at the frequency that is causing the feedback. Are you looking for feedback in a certain frequency range or on a particular note? Skillful EQ boosting in the appropriate frequency range will often help bring out feedback. 

• Try placing a graphic EQ in front of a phase shifter or flanger pedal. Boost or cut a band to accentuate or reduce the "swish" of the pedal in that frequency range.

• Some delay pedals have a built-in effect loop - by patching in an EQ pedal, you can make the delay repeats get progressively brighter or darker.

• Low frequencies require more power to amplify than high frequencies, so if you're trying to get the maximum "clean volume" out of your amp, try rolling off some of the low frequencies; in particular, the area below 100Hz usually adds little to the sound of the guitar, but it can be a drain on headroom.

• Do you ever switch back and forth between two different guitars? If one guitar has humbuckers, and the other uses single coils, it may be difficult to find an EQ setting on your amplifier that works well with both instruments. An EQ pedal can be used to compensate; just kick it on or off when you switch instruments and you won't need to be constantly adjusting your amp settings.

• When trying to make sonic "corrections" with a parametric EQ, boost heavily and then slowly "sweep" the frequency knob until the offensive sounding frequency really "jumps out" at you--then just cut it back until it sounds good.

• Many EQ pedals include an output level slider. Turn it up and use your EQ pedal as a "clean boost", or to kick your "on the edge" tube amp into full overdrive. Add in some mid and high frequency EQ boost, and your solo will cut through the densest mix.

• Running an EQ pedal in your amp's effects loop allows you to adjust the overall sound of the preamp right before it hits the output / power amp stage.

• Small all-tube practice amps such as the Fender Champion 600 or Vox AC4 sound great, but are usually very restricted in terms of their EQ sections (Figure 5); if they have any tone controls at all, it is usually limited to a single knob. Adding an EQ pedal right before the amp will allow you to adjust the tone to a far greater degree than you can with the amp's limited EQ.

Figure 5: An EQ pedal can greatly increase the tone shaping capabilities of small tube practice amps with minimal controls, such as the Fender Champion 600 (top) and Vox AC4 (bottom).