The Pultec EQP-1A

Original Pultect EQP 1A

The Pultec EQP-1A Equalizer has been shaping the sound of recorded music for more than half a century. Known for its smooth, natural tone and simple design, it remains one of the most respected pieces of studio equipment ever made.

History of the Pultec EQP-1A Equalizer

The Pultec EQP-1A Equalizer is one of the most iconic and enduring pieces of studio hardware ever built. Designed in the 1950s by Pulse Techniques, the EQP-1A combined passive equalization with a tube amplifier stage to deliver uniquely smooth, musical tone shaping. Its design allowed subtle or broad frequency adjustments that enhanced sound without harshness, making it a favorite across decades of recording and mastering.

Origins of Pulse Techniques

Pulse Techniques was founded in 1953 in Teaneck, New Jersey, by Eugene “Gene” Shenk and Ollie Summerlin. Both were trained in electronics and radio technology, spending years designing test and measurement equipment before moving into professional audio. Their precision-oriented background led them to design an equalizer that could shape frequencies cleanly and musically, without adding unwanted distortion or noise.

At the time, most equalizers were active designs using amplifiers to boost or cut frequencies. Shenk and Summerlin took a different approach, building a passive filter network made of resistors, capacitors, and inductors, followed by a vacuum tube amplifier to restore gain. This combination became the foundation of the Pultec sound.

The First Model: EQP-1

In 1956, Pulse Techniques released the original EQP-1 Program Equalizer. It offered independent controls for boosting and cutting both low and high frequencies—a rare feature at the time. The EQP-1 used high-quality transformers and vacuum tubes, giving it a subtle character even when set flat.

Engineers quickly discovered that by boosting and cutting at the same low frequency, they could tighten the bottom end while retaining depth. This became known as the “Pultec trick,” a technique still used today in both analog and digital studios. (See below.)

The Evolution to the EQP-1A

In 1961, Pulse Techniques refined the design and introduced the EQP-1A, expanding the frequency options and improving control flexibility. The EQP-1A added a variable bandwidth control for the high boost section, allowing for more precise tonal shaping. Its low-frequency range included 20, 30, 60, and 100 Hz options, while the high-frequency boost and attenuation bands extended up to 20 kHz.

This model preserved the same passive circuitry and tube amplification that defined the original, but it became more versatile and easier to integrate into professional setups.

Later Models and Modern Revival

By the early 1970s, Pulse Techniques released the EQP-1A3, a smaller 2U rackmount version designed for modern studio racks. Later, a solid-state version known as the EQP-1A3SS replaced the tube amplifier with transistor circuitry, offering a cleaner sound, but without the same character.

Despite its success, Pulse Techniques closed in 1981 after Gene Shenk retired, leaving behind a legacy of audio craftsmanship. For decades, original Pultec units became rare collector’s items, prized for their sonic magic and hand-built quality.

In the early 2000s, audio engineer Steve Jackson revived the Pulse Techniques name, working directly from the original blueprints and component specifications. These reissued EQP-1A units faithfully recreated the sound and construction of the 1960s models, returning the Pultec name to professional studios worldwide.

Timeline of Key Versions

  • 1953 – Pulse Techniques founded by Eugene “Gene” Shenk and Ollie Summerlin
  • 1956 – Original EQP-1 Program Equalizer introduced
  • 1961 – EQP-1A released with added frequency choices and bandwidth control
  • Early 1970s – EQP-1A3 introduced in a 2U rack format
  • Late 1970s – EQP-1A3SS solid-state version released
  • 1981 – Pulse Techniques factory closes
  • 2000s – Steve Jackson revives Pulse Techniques with faithful EQP-1A3 reissues

Software Emulations

  • Universal Audio Pultec Passive EQ Collection (EQP-1A, MEQ-5, and HLF-3C)
  • Waves PuigTec EQP-1A and MEQ-5 Bundle
  • Apogee Pultec EQP-1A Plugin
  • IK Multimedia T-RackS EQP-1A
  • Softube Tube-Tech PE 1C (Pultec-inspired design)

Tips and Techniques

  • Use the Low Band Boost and Attenuation Together

    eqp 1a operations advice

    Sometimes, it’s good to disregard the operations manual! See: Go ahead, boost and attenuate. The Pultec EQP-1A.

  • Shape High Frequencies with the Bandwidth Control

    Choose a High Boost frequency between 8 and 10 kHz for clarity and definition, then adjust the Bandwidth knob to set how wide the boost spreads. Narrow bandwidth settings enhance specific elements like vocal air or cymbal detail, while wider settings create a smoother lift across the upper range.

  • Apply Subtle EQ Moves During Mastering

    The EQP-1A’s curves are broad and overlapping, so small changes go a long way. When mastering, limit boosts or cuts to 1–2 dB. Use the low shelf to enhance weight and the high boost for definition.

  • Smooth Harsh Top End with High Attenuation

    Use the High Attenuation control at 5 or 10 kHz to tame brittle high-end material. Set the High Boost to 8 or 10 kHz, then dial in a small amount of attenuation to balance the response. This simultaneous boost and cut creates a gentle, natural roll-off ideal for bright cymbals, acoustic guitars, or overly crisp mixes.

  • Run Audio Through Flat Settings for Subtle Coloration

    Set all EQ controls to zero and pass your audio through the EQP-1A hardware or a plugin model. Even without EQ engaged, the circuit introduces mild saturation and transformer interaction.

  • Stack Multiple Instances for Layered Control

    Use two plugin instances in series: one focused on low-end control (using the 20–60 Hz range) and another for high-end shaping (8–16 kHz). The first instance stabilizes the foundation, while the second adds clarity and openness without any interaction between the two bands..

  • Experiment with Bandwidth and Gain Interactions

    The Bandwidth knob influences not just the range of frequencies affected but also the gain shape of the boost. Wide bandwidth settings produce more gradual curves, while narrow ones create a defined peak. On program material, start wide and narrow gradually until the EQ enhances rather than reshapes the sound.

  • Integrate with Compressors in Serial or Parallel Chains

    Use the EQP-1A before a compressor to sculpt tone prior to dynamic control, or after it to restore clarity lost in compression, or both. Andrew Scheps has a “famous” technique he uses. Look it up!