“Three knobs representing three EQ bands: Low, Mid and High, with the outer casing of the knob controlling the frequency and a smaller internal knob the level. There is a fourth knob to control the overall volume +/- 18db. Pretty self explanatory once you know what you’re doing.”
“Very quiet for an EQ, with a slight hiss when the “high” volume knob is turned up fully. Although it’s designated a Bass EQ, it can work on any electric instrument as its frequency range is from 25Hz to 16kHz.”
“Whether you use a solid state or tube amp this pedal can be used to “tune” your sound for each piece of gear and for each room/venue. Because the frequency range is so wide, it can be used effectively for guitar, bass, vocals, and even a DJ setup. This is one of my favorites.”
“You can use it as a bass boost, a solo (mids) boost, a treble boost, cut some bass from a poorly EQed fuzz, a simple volume boost to drive your amp a little harder, maybe even a kill switch. Unless you must have more than 18dbs of boost, I’d choose this over other “clean boosts” like the MXR Micro Amp, Zvex SHO etc. Way more versatility at a fraction of the cost.”
“Pretty easy to use as long as you know what a parametric equalizer does. It controls bass, mid-range, and treble with a range of 25 Hz to 16 kHz. This is close to the extent of human hearing. Each parameter and the overall volume is adjustable from +/-18 dB.”
“Tone can be stretched in ridiculous ways with this device. Through extreme knob turning there is not a bit of background noise. The +/-18 dB range is pretty extreme, but it is indeed that flexible. On most parametric and graphic equalizers, it is difficult to create convincing sounds when you stretch a knob or slider beyond +/-12 dB. That flexibility is available with this effect. This pedal is awesome as a customizable clean boost — that is where the +/-18 dB range comes in handy.”
“Boss PQ-3B Bass Parametric Equalizer pedal. 18dB of boost (the most of any Boss EQ pedal) or cut across low, middle and high bands. Level and frequency controls for each band for dialing your sound. Overall level control as well.”
More information on this effect can be found here.