Pultec EQP-1A Program Equalizer

Pultec EQP-1A Program Equalizer is a tube passive equalizer in a 3U chassis with the classic blue front panel, built by Pulse Techniques from the same components as the units made between 1961 and 1981. The equalization section is entirely passive: the filters attenuate, and a tube line amp on 12AU7, 12AX7 and 6X4 restores the level. That gain stage shapes the sound as much as the curves do, which is why the unit leaves its mark on a signal even with every control at zero.

More weight and less mud in a single move

Low-frequency boost and attenuation work on the same selected frequency but follow different curves, so you can lift 60 Hz by a few decibels and cut with the attenuator at the same setting. The bottom gains mass while the band immediately above it loses the excess that normally clouds kick and bass. No single parametric filter reproduces this, because the effect comes from two circuits interacting inside one passive network. The range is generous: up to 17.5 dB of cut against 13.5 dB of boost, enough to reshape a full drum bus.

Top end that opens up instead of stinging

High-frequency peak boost offers seven centres from 3 to 16 kHz plus a bandwidth control, and that control is what makes the section usable in practice. A wide curve at 10 or 16 kHz opens vocals and overheads without dragging sibilance forward, because the peak stays gentle and spread out. Narrowing the bandwidth turns the same knob into a presence tool at 3 or 5 kHz for guitars or snare. A separate high shelf attenuator at 5, 10 or 20 kHz, up to 16 dB, lets you pull excess air off a saturated bus at the same time, without touching the band you just lifted.

KEY FEATURES

• Fully passive equalization network with a tube line amp restoring level
• 3U chassis with the blue front panel in the original 1961-1971 layout
• Simultaneous low-frequency boost and attenuation at the same frequency
• Four low-frequency centres: 20, 30, 60 and 100 Hz, boost and cut
• Seven high-frequency peak centres from 3 to 16 kHz with bandwidth control
• High shelf attenuation at 5, 10 and 20 kHz
• 600 Ohm input and output transformers
• Identical components and specifications to the 2U EQP-1A3

TECHNICAL SPECIFICATIONS

• Type: passive program equalizer with tube line amplifier
• Low shelf boost: 20, 30, 60, 100 Hz, 0-13.5 dB
• Low shelf attenuation: 20, 30, 60, 100 Hz, 0-17.5 dB
• High peak boost: 3, 4, 5, 8, 10, 12, 16 kHz, 0-18 dB
• High shelf attenuation: 5, 10, 20 kHz, 0-16 dB
• Input impedance: approx. 600 Ohms
• Output impedance: approx. 50 Ohms
• Noise: 92 dB below +10 dBm
• Distortion: 0.15% max at +10 dBm into 600 Ohms
• Amplifier response: 20 Hz to 20 kHz, +/- 0.5 dB
• Tubes: 12AU7, 12AX7, 6X4 (one each)
• Height: 3U (5.25 inches)