Pultec EQM-1S3 Program Equalizer

Pultec EQM-1S3 Program Equalizer in its mastering version pairs the widest curve set in the tube Pultec line with fully stepped controls in a 2U chassis. The basis is the EQP-1S3: low curves at 30, 40, 70 and 100 Hz, nine high peak centres including 1 and 2 kHz, 5 and 10 kHz shelf boost, and separate shelf attenuation. The potentiometers are replaced by 21-position ELMA switches, with bandwidth on an 11-position switch.

Stepped controls where the sections interact

Pultec curves are not isolated from each other: boosting and attenuating the lows at once makes both sections influence one another, and the effective step stops matching its nominal value. On potentiometers that means a setting only holds meaning until you move it. On switches every position is a number you can write down, so you can return to exactly the same configuration a week later and compare two versions without guessing. The 1S3 has more overlapping sections than anything else in the line, so it benefits most.

Mastering precision with headroom for track work

The full-range taper gives 0.5 dB per step through the first half of rotation, growing to 1 or 2 dB beyond 50%. One scale therefore covers half-decibel moves on a mix bus and the full 18-20 dB when the same equalizer lands on an individual track. Precision metal film resistors at every position keep units consistent with each other, which on stereo material is what holds the image in place. All equalization stays passive, with level restored by the tube line amp on 12AU7, 12AX7 and 6X4.

KEY FEATURES

• Mastering version of the EQP-1S3 in a 2U chassis
• The widest curve set in the tube Pultec line
• 21-position ELMA switches instead of potentiometers, 11-position bandwidth switch
• Precision metal film resistors giving each control its own taper
• Full-range progressive taper: 0.5 dB per step across the 0-5 dB range
• 5 and 10 kHz high shelf boost alongside nine peak centres
• Simultaneous low-frequency boost and attenuation at the same frequency
• Repeatable settings and unit-to-unit matching for stereo work

TECHNICAL SPECIFICATIONS

• Type: passive program equalizer with tube line amplifier, stepped controls
• 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, 0-14.5 dB
• High shelf attenuation: 5, 10, 20 kHz, 0-16 dB
• Controls: 21-position switches, 11-position bandwidth switch
• Input impedance: approx. 600 Ohms, output 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: 2U (3.5 inches)