Pultec founders Gene Shenk and Ollie Summerland unveiled the first passive program EQ in 1951. This EQP-1 was based on filter circuits licensed from Western Electric and sounded great, but suffered the gain insertion losses typical of any passive filter, so the duo upgraded their original unit to the EQP-1A, which followed the EQ section with a gain makeup stage using a push-pull design with 12AU7, 12AX7 and 6X4 vacuum tubes. Designed for broad equalization of program material, the EQP-1A had four low boost/cut frequencies, three high-cut frequencies and a choice of seven HF boost points, along with a bandwidth control for shaping the high boost curve.
Like many boutique entrepreneurs, Shenk and Summerland built every unit to order by hand in their true two-man operation. Other Pultec units included the EQ-H2 high-frequency equalizer, the MEQ-5 mid-band EQ and the EQP-1A3 (an EQP-1A in a two-rackspace chassis), as well as solid-state versions, which had silver-face front panels. The company folded decades ago, but its spirit lives on in products such as Manley Lab's Enhanced Pultec EQP-1A, an updated version with improved sonic performance.