Classic American 4-Band EQ-Preamp

Following in the footsteps of its simpler three band P50A brother, the EQ P50B module expands in flexibility by adding a fourth EQ band.

This module is so great sounding because of the rather simple all-discrete circuit schematic of the original hardware it's based on, whose key point is the 2520 op-amp. Its four peaking bands with seven selected frequencies cover the whole spectrum and then some. It also allows for the overlapping of bands for complex EQ shapes — this is invaluable in mixing sessions where the proper EQ is the key to finding the right balance and position of a track within a mix.

Simplicity, though, doesn't mean lack of tone: the EQ P50B doesn't have many of the bell and whistle features others offer — like complex and eye-catching but oftentimes distracting displays. The ease of use of its two knobs per band enhances the analog feel of the module by providing the instant gratification of turning a knob and hearing a result.

The same "make it better" approach to the user interface of the digital model applied to the 3 band version was kept in the EQ P50B: the dual concentric knobs of the original hardware have been split for better usability and an uncluttered view. Band gain is also stepped in 1 dB (1.5 dBs towards the end of throw) increments for finer resolution.

The four band design is particularly useful for exploring all of the complex facets of midrange critical tracks, like guitars, vocals, pianos or strings. Having two midrange dedicated bands — that span from 75Hz to 12.5KHz overlapping in some points — allows it to perform a variety of boosts and cuts that will shape the track and make it fit. Low and high bands can be conveniently switched to shelving mode for broader strokes if needed.

As with the EQ P50A, the proportional Q design plays a particular role in this EQ, especially in dense and complex mixes. This kind of design sharpens the Q of any given band as the gain is increased (or cut) from a broad, gentle shape at low gain levels to a narrow Q at extreme values. This approach results in two benefits: phase shifting is minimized and no additional controls are needed for bandwidth management.

To round out the pack, the same preamp circuit used in the EQ P50A is also onboard on this module. This means that the sonic envelope of this four band EQ can be pushed further. The interaction between the preamp stage and EQ is a crucial factor in finding many tonal variations of the same track. Engaging the preamp and boosting its gain makes the following components — from the filters network to the output transformer — react different and this actually more than doubles the sonic possibilities offered. This makes it more than a simple EQ, but instead a complex yet simple to use "tone machine".

When the preamp is disengaged the Gain and Out controls act as clean input and output levels to the EQ section for handy adjustments.