Parametric EQ: What it is, How to Use it and Why. - MasteringBOX
Carl Martin 3 Band Parametric EQ Guitar Pedal - AVLgear.com
Guitar Pedal X - GPX Blog - Muir Audio Design's Morphtone EQ - a Morphing Dual Parametric EQ - delivers an innovative and powerful new way for shaping your instruments' output tone
Parametric EQ
Carl Martin 3-Band Parametric EQ/Pre-amp | Guitar Center
t. c. electronics Classic Sustain + Parametric EQ | Vintage guitars and amps