The Pultec EQP-1A Program Equalizer is a legendary, tube-based, passive equalizer known for its unique ability to simultaneously boost and cut at the same frequency. Originating in the 1950s, this EQ became a studio legend and is still used today for adding richness and clarity.
The EQP-1A is a gold standard in analog equalization, with the original units being highly revered and sought after by engineers for over 70 years. This has led to many hardware and software "re-creations" that aim to capture its legendary sound. The EQP-1A uses a two-band design with separate low-frequency shelving and high-frequency peaking/shelving controls to add warmth and character to audio sources like vocals, bass, and drums, making broad tonal shaping and fixing issues in the low end a specialty. As a tube equalizer, it imparts a rich, warm, and smooth tone that enhances audio rather than simply adjusting it, a hallmark of vintage analog equipment. It excels at broad, musical EQ moves, making it ideal for sweetening vocals, adding punch to bass, and enhancing guitars.
The EQ section itself is passive, with a tube-driven gain make-up stage added to compensate for the signal loss introduced by the filters. The Low-Frequency section features a shelving EQ for boosting and cutting at selectable frequencies like 20, 30, 60, and 100Hz. The High-Frequency section of the equalizer offers a peaking boost with selectable frequencies and a separate, adjustable-bandwidth control to shape the Q of the boost curve. It also includes a high-frequency shelf cut for reducing unwanted brightness.
Pultec EQP-1A Program Equalizer Features
- Two-band tube equalizer: Features independent controls for low-frequency shelving and high-frequency peaking and shelving.
- The "Pultec trick": Allows the simultaneous boost and attenuation of the same low-frequency shelf. The boost circuit has a wider Q (bandwidth) and the cut circuit a narrower one, which results in a broad boost with a gentle dip around it. This creates a tight, powerful bass sound without muddiness, which is especially popular on kick drums and bass guitars.
- Passive EQ with tube gain-makeup: The equalization is achieved through a passive, inductor-based circuit. The unit features a separate tube-driven amplifier stage to restore the signal strength lost by the passive filters, adding a unique, harmonically rich coloration.
- Independent high-frequency controls: Separate frequency selectors are available for the high-frequency boost and high-frequency shelf cut. This allows for precise high-end shaping, such as boosting a peak at 12kHz for "air" while using a shelf cut at 5kHz to tame harshness.
- Adjustable high-frequency bandwidth: The "Bandwidth" control adjusts the Q of the high-frequency boost, from a sharp, focused peak to a broader, more musical bell shape.
- Subtle but powerful sound: The EQP-1A is capable of both broad, gentle equalization and more aggressive tone shaping. It is often praised for making audio sound "better just by passing through it," even with minimal or no EQ applied.
- Intuitive interface: Despite its unique design, the controls are simple and straightforward, facilitating a quick and musical workflow.
- Vintage components: The original and faithful reissues are built with transformers and vacuum tubes that contribute to its celebrated vintage tone.
Pultec EQP-1A Program Equalizer Specifications
- 20, 30, 60, 100 CPS (Hz) shelf boost, 0 – 13.5 dB
- 20, 30, 60, 100 CPS shelf attenuate, 0 – 17.5 dB
- 3, 4, 5, 8, 10, 12, 16 KCS (kHz) peak boost, 0 – 18 dB
- 5, 10, 20 kcs shelf attenuate, 0 – 16 dB
- Input Impedance: ~600 Ohms
- Output Impedance: ~50 Ohms
- Noise: 92 dB below +10 dBm
- Distortion: ≤ 0.15% at +10 dBm into 600 Ohms
- Amplifier: Flat, 20 CPS to 20 KCS, +/- 0.5 dB
- Tubes: 1 ea 12AU7, 12AX7, 6X4
Pultec EQP-1A Program Equalizer Includes
- Pultec EQP-1A Program Equalizer
- Power Cable
- Manufacturer Warranty
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