Pultec HLF-3C

The HLF-3C is the collection's simple filter processor, not another boost-and-cut program equalizer. Its two 12 dB/octave cut filters remove material below and above selected frequencies, allowing broad cleanup of an instrument or subgroup, or deliberately narrow-band effects.

Unlike the amplified EQP-1A and MEQ-5 hardware, the HLF-3C was entirely passive and had no input/output amplifiers. The plug-in compensates the hardware's inherent insertion loss, giving unity gain on insertion before filtering removes signal energy. It should therefore not be described as a tube-drive processor just because it belongs to the same collection.

Begin with the broadest useful passband, move one cutoff at a time, and check the result in the arrangement. A low cut can make room below an instrument; a high cut can reduce unnecessary brightness or push it toward a restricted-band character. Enable is a full bypass here, unlike the EQ-only switches on the amplified Pultecs. There are only three controls, so no hidden gain, resonance, or bandwidth parameter is implied.

Manual — sections: Pultec HLF-3C; Pultec HLF-3C Controls; Unity Gain.

• Enable: The up position activates filtering; down bypasses the complete plug-in. This differs from the EQ Enable switches on EQP-1A and MEQ-5, where modeled amplifier circuitry remains active. Because HLF-3C has no such amplifier path to preserve, its switch is a true whole-processor comparison. Use it frequently while listening in the mix rather than judging only the isolated track.
• Low Cut / CPS: The manual lists 50, 80, 100, 150, 250, 500, 750, 1000, 1500, and 2000 Hz. This is the high-pass side: moving upward removes progressively more low-frequency material at 12 dB/octave. Start below the source's useful body and increase only until unwanted energy is reduced. High settings intentionally remove much of the fundamental range and are better treated as an effect than transparent cleanup. CPS means Hz.
• High Cut / KCS: The listed cutoffs are 1.5, 2, 3, 4, 5, 6, 8, 10, 12, and 15 kHz. This is the low-pass side, also at 12 dB/octave. Lower settings progressively darken or restrict the signal. Compare several neighboring positions before moving the low cut again, so the contribution of each filter stays clear. KCS means kHz.
• Frequency shortcuts: Click the relevant CPS or KCS label to advance through selections, or shift-click to move backward. These change cutoff positions; they do not provide continuous sweeps, resonance, or slope adjustment.
• Level and documentation limits: There is no output-gain knob. Unity-gain compensation removes the hardware's basic insertion loss, not the audible level reduction caused by filtering out musical energy. Use downstream gain if a loudness-matched comparison is needed. The manual calls each selector eleven-position but enumerates ten numeric frequencies; the lists above reproduce only the explicitly documented frequencies rather than inventing another cutoff.

Manual — sections: Pultec HLF-3C Controls; Unity Gain; Enable; Low Cut; High Cut.