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THE PQ-4 is quite rare. It was never a big seller and as Boss doesn’t make any parametric equalizers today (2004) they are quite sougth after. You can adjust Presence, Low Level boost or cut, Mid Frequency range between 100Hz and 1.6 KHZ , and a High Frequency range between 500HZ and 8KHZ. Each frequency range selector has it’s own individual levels for boosting or cutting specific frequencies, plus it has a -18 to +18 over all level boost or cut.

Boss Guitar Effects Guide Book vol.9 (1993):

For the first time, a compact pedal with concentric knobs for presence and three frequency bands. Each frequency band and equalization curve is ideally suited for guitar use, and each control adjusts over a +/-18dB range. The PQ-4 allows users to get a variety of sounds comparable to using several guitar amps, or different types of pickups and guitars.

BOSS PQ-4 Parametric Equalizer

Using the PQ-4

  • To change a strat-type sound to a telecaster-type sound: Boost the extreme high frequencies using the PRESENCE control and cut the highs a little to get a dry telecaster sound (Fig 1: Low 3, Presence 8, Mid Freq 5, Mid Level 5, High Freq 7, High Level 2, Level 5)
  • To produce an acoustic guitar sound: Cut the extreme low frequencies using the PRESENCE control and boost the middle and high frequency bands to produce a warm sound (Fig 2: Low 1, Presence 5, Mid Freq 2, Mid Level 6, High Freq 3, High Level 6, Level 5)
  • To get the mid-range sound of a large amp: Boost the extreme high frequencies with the PRESENCE control and boost the mid frequency band with the MIDDLE level and frequency controls. (Fig 3: Low 7, Presence 8, Mid Freq 2, Mid Level 6, High Freq 5, High Level 5, Level 5)


  • Controls: Presence/Low, Middle, High, Level
  • Connectors: Input, Output, AC Adaptor
  • Current Draw: 23mA
  • Weight: 410g
  • Input Impedance: 1 Mohm
  • Output Impedance: 1 kohm
  • Residual Noise Level: less than -98dBm (IHF-A)
  • Recommended Load Impedance: More than 10kOhm
  • Recommended AC Adaptor: PSA Series


  • Silver – Made In Taiwan

The PQ-4 was sold from March 1991 to November 1997.