Retro Instruments 2A3 is a dual-channel tube program equalizer in a 2U chassis, built around fully passive capacitor and inductor equalization. Its curves follow the standard set by the Pultec equalizers, with the set of high-frequency boost centres extended by several additional points. Level is restored by a class AB tube amplifier running at unity gain on two 12AX7 and two 12AU7 tubes, with custom-designed transformers.
A subsonic filter for peaking low-frequency boosts
Classic passive equalization adds excess energy below the useful band when you boost the lows, which on subwoofer-equipped monitors and club systems eats headroom for no audible return. The 2A3's subsonic filter handles this differently from a plain highpass: it works through the interstage transformer and offers 40 and 90 Hz settings with a peaking response and a sharp cutoff, turning a shelf boost into a lift with a defined peak. The 40 Hz setting takes nothing off the bottom while adding energy around 35 to 40 Hz. The filter switches out whenever material calls for tight, accurate low-frequency response.
Two channels and ten high-frequency centres in one unit
Both channels fit into 2U with separation exceeding 70 dB, so you can work in stereo, across two independent tracks, or cascaded, feeding one channel into the other for extended equalization. High-frequency boost offers ten centres from 1.5 to 16 kHz, more than the original passive designs, which lets you place a single track in a mix more precisely or add presence to a vocal without moving into the sibilance band. The low section keeps the simultaneous boost-and-cut arrangement that scoops out mud and adds punch to kick and bass. The knob scales carry a hundred positions, so settings are reproducible.
KEY FEATURES
- Two channels of tube program equalization in a 2U chassis
- Fully passive capacitor and inductor equalization with no feedback loop
- Curves consistent with the Pultec equalizer standard
- Ten high-frequency boost centres from 1.5 to 16 kHz
- Subsonic filter at 40 and 90 Hz coupled through the interstage transformer
- Simultaneous low boost and cut in the classic Pultec arrangement
- Hundred-position knob scales for reproducible settings
- Channel separation above 70 dB
- Class AB tube amplifier at unity gain
- Equalization bypass switches per channel
TECHNICAL SPECIFICATIONS
- Low-frequency boost: 20, 30, 60 and 100 Hz
- Low-frequency cut: 20, 30, 60 and 100 Hz
- High-frequency boost: 1.5, 3, 4, 5, 6, 8, 10, 12, 14 and 16 kHz
- High-frequency cut: 5, 10 and 20 kHz
- Subsonic filter: 40 and 90 Hz, peaking response with sharp cutoff
- Signal-to-noise ratio: greater than 76 dB
- Channel separation: greater than 70 dB
- Frequency response: flat within 1 dB, 20-20,000 Hz
- Harmonic distortion: below 1%, 20-20,000 Hz
- Input and output: 600 Ohms, fully floating, transformer balanced, XLR
- Tubes: 2x 12AX7 and 2x 12AU7, jumper-selectable 6 or 12 volt heater configuration
- Dimensions: 2U, 19 x 3.5 x 9 inches, IEC power 115/230 V, 50-60 Hz
