Pultec EQP-1S Program Equalizer

Pultec EQP-1S Program Equalizer is the 3U version of the formerly very rare EQP-1S, returned to production after the EQP-1A in response to customer requests. The line amp is the one used across the 1A family: wide-bandwidth, tube-based, on 12AU7, 12AX7 and 6X4. The differences sit in the passive section, and they are functional rather than cosmetic: reshaped low-frequency curves, two extra peak centres, and something the 1A family does not have at all, high-frequency shelf boost.

A shelf on top, not only a peak

The 1A and 1A3 lift highs with a peak curve only, so the response falls away again above the chosen centre. The EQP-1S adds shelf boost with 5 and 10 kHz corners, up to 14 dB, which raises the whole top end and stays raised. For vocals, strings and a mix bus that is a different tool from a 10 kHz peak: it adds air across the range instead of emphasising one band. Because both sections operate at once, you can hold the shelf as a general tilt and use the peak separately to place presence at 3 or 5 kHz.

Two extra centres where the voice lives

Peak boost offers nine centres, since 1 and 2 kHz join the set inherited from the 1A. That band decides vocal intelligibility and whether a guitar cuts through a backing track, and the 1A family had no access to it at all. The low curves move up to 30, 40, 70 and 100 Hz, giving a higher point of leverage than the 20 Hz of the 1A and working better on material where the lowest octave is already occupied. Low boost and attenuation still act on the same frequency simultaneously, so the classic simultaneous lift-and-cut settings remain available.

KEY FEATURES

• Passive equalization network with a tube line amp restoring level
• 3U chassis with blue front panel
• High-frequency shelf boost with 5 and 10 kHz corners, absent from the 1A family
• Nine high-frequency peak centres, including 1 and 2 kHz
• Low-frequency curves shifted to 30, 40, 70 and 100 Hz
• Simultaneous low-frequency boost and attenuation at the same frequency
• The same wide-bandwidth line amp as the EQP-1A and EQP-1A3
• 600 Ohm input and output transformers

TECHNICAL SPECIFICATIONS

• Type: passive program equalizer with tube line amplifier
• Low shelf boost: 30, 40, 70, 100 Hz, 0-13.5 dB
• Low shelf attenuation: 30, 40, 70, 100 Hz, 0-17.5 dB
• High peak boost: 1, 2, 3, 4, 5, 8, 10, 12, 16 kHz, 0-18 dB
• High shelf boost: 5, 10 kHz, 0-14 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)