551 Inductor EQ

The 551 Inductor EQ is the only equalizer for the 500 Series actually designed by Rupert Neve. Featuring 3 bands of EQ inspired by Mr. Neve’s most prized vintage designs, along with custom-wound inductors, transformers and class-A gain blocks, the 551 brings the thick, powerful lows and sweet highs of Rupert’s classics to the 500-Series format for the very first time.

The “Best-Of” EQ

The 551’s 3-band, custom-tapped inductor EQ was inspired by our favorite elements of Rupert’s vintage EQ designs. The low frequency band is designed to produce a creamy, resonant bass response similar to a vintage 1064 – but unlike the vintage modules, the LF band on the 551 can be used as either a shelf or a peak filter, adding punch, dimension, and control to your low end.

The midrange band is based on that of the 1073, ideal for sweetening vocals and instruments while bringing them forward in a mix, and its proportional “Q” response makes it well-suited for minimizing problematic frequencies. The high frequency band is a hybrid vintage / modern design, blending inductor circuitry with capacitor-based topologies to achieve vintage tones with enhanced control. The High Pass filter is a 12dB/octave design with a fixed 80Hz frequency, and can be used in tandem with the low frequency EQ to add low-end presence without clouding the source material.

As with Rupert’s most prized classic designs, each EQ section uses low-feedback, class-A discrete electronics to prevent low-level artifacts and harshness from detracting from the tonal shaping. However, this new circuit is a decidedly modern design with updated techniques and components that were simply not available 50 years ago, and is definitely not a “clone”.

EQUALIZER BYPASSED

NOISE
Measured at Main Output, un-weighted, 22Hz-22kHz, source impedance 40 Ohm balanced. Noise specifications may vary depending on which 500 series chassis is being used, and / or interference from stray magnetic fields.
Better than -102 dBV

FREQUENCY RESPONSE
Main output, no load: +/- 0.1 dBu from 20 Hz to 31.5 kHz, -1 dB @ 120 kHz

MAXIMUM OUTPUT LEVEL 
23.25 dBu

TOTAL HARMONIC DISTORTION AND NOISE
@ 1 kHz, +20 dBu output level, no load: Better than 0.0025%
@ 20 Hz, +20 dBu output level, no load: 0.13% Typical (2nd and 3rd harmonic)

HIGH PASS FILTER
-2.7 dB @ 80 Hz
Slope: 12 dB/Octave

EQUALIZER ENGAGED

NOISE
Measured at Main Output, un-weighted, 22 Hz - 22 kHz, source impedance 40 Ohm balanced.
Better than -94 dBV

FREQUENCY RESPONSE
Main output, no load: +/- 0.25 dBu from 20 Hz to 45 kHz, -2 dB @ 120 kHz

MAXIMUM OUTPUT LEVEL 
23 dBu

TOTAL HARMONIC DISTORTION AND NOISE
@ 1 kHz, +20 dBu output level, no load: Better than 0.009%
@ 20 Hz, +20 dBu output level, no load: 0.13% Typical (2nd and 3rd harmonic)

POWER REQUIREMENTS
120mA on +16VDC
110ma on -16VDC