Typically, the circuit employs a 12AU7 (ECC82) and a 12AX7 (ECC83) . In some vintage versions, a 6AU6 is used as the input pentode.
In a world of linear-phase digital EQs and AI mixing tools, why obsess over a 70-year-old passive design? pultec eqp-1a schematic
While not on the EQ schematic, the power supply and amplifier schematic are vital. Most "Pultec EQP-1A" reissues integrate a 12AX7 and 12AU7 gain stage. The high plate voltage (250V+) and the unbypassed cathode resistors are what give the unit its slow, sweet saturation when driven hard. Typically, the circuit employs a 12AU7 (ECC82) and
Original schematics from the 1950s show unbalanced inputs and outputs. Later versions (like the EQP-1A3) added balanced transformers. Many DIY schematics online accidentally mix these sections, creating an impedance mismatch. creating an impedance mismatch.