Reportedly used by The Edge, David Gilmour, and Adrian Legg, this discontinued box of vintage Danish sonic wizardry boasts a huge range and precision carving capabilities. The DPE is a rare bird, and a weird bird as well, but it's guitar sculpting powers are a thing of legend. The Boss PQ-4 is not uncommon to find on the used market for between 80 and 120 dollars. The best thing about the PQ-4 is its smooth, quiet, musical personality, which avoids the harsh artificiality of lesser EQs, and makes this pedal ideal for getting the most out of overdrive and distortion boxes. The selected frequency range can be boost or cut a hefty 18dB, and overall level can also be boost or cut by the same amount, giving the PQ-4 a lot of power to slice and dice a guitar sound. It offers broader shelving equalization for low frequencies and high presence, while mid frequencies are variable between 100Hz and 1.6kHz, and the high range covers from 500 Hz to 8kHz. Since then it has gained something of a reputation for versatility, quiet operation, and the very musical way in which it pairs with dirt pedals. Manufactured from '91–'97, the PQ-4 was not a huge hit during its production run, likely being overshadowed by Boss's stalwart GE-7 graphic EQ. This sadly discontinued gem from Boss is an excellent early example of a semi-parametric EQ circuit designed for the pedalboard. Here is a grip of our favorite parametric-style EQ's for guitarists who want to bring the power of these potent tone shapers to their pedalboards. The advantages of a parametric or semi-parametric EQ are significant, as they offer much more precise control over amplitude, bandwidth, and center frequency than other varieties.
PARAMETRIC EQ PROFESSIONAL
Parametric EQs are familiar to anyone who knows their way around a recording studio, and are the primary sonic carving knife of most professional recording engineers. These can be excellent, and are all that's needed for many players, but for guitarists who really want to get into deep, surgical tone shaping, a parametric EQ is ideal.
Most EQs for guitar are of the simple graphic variety, with tiny sliders that boost or cut specific, pre-set frequencies. These are just a few examples that illustrate the great creative potential of the EQ pedal. In addition to sprucing up a less-than-stellar base sound or compensating for unexpected stage or monitoring anomalies at gig time, a good equalizer can help a solo cut through the mix, breathe new life into an old drive or distortion pedal, and help create rich textures that would otherwise not be possible.
PARAMETRIC EQ GENERATOR
Often ignored or written off by guitarists as a mundane utility item, or a sonic Band-Aid of sorts for a fundamentally flawed tonal foundation, the lowly EQ pedal is a powerful, yet frequently overlooked generator of great tones.
I've written in these pages before about the sometimes-maligned, always-underestimated EQ pedal.