551 - Audio Mixer Rupert Neve Designs - Free user manual and instructions

Product Type	500 Series Inductor EQ
Dimensions (H x W x D)	1.5 inches (3.81 cm) x 5.25 inches (13.34 cm) x 7 inches (17.78 cm) (approx.)
Weight	1 lb (0.45 kg) (approx.)
Power Requirements	+/- 16 VDC supplied by 500 series rack; +16V @ 120 mA, -16V @ 110 mA
Frequency Response (EQ bypassed)	+/- 0.1 dB from 20 Hz to 31.5 kHz; -1 dB @ 120 kHz
Maximum Output Level	23.25 dBu (EQ bypassed), 23 dBu (EQ engaged)
THD+N (1 kHz, +20 dBu out)	Better than 0.0025% (EQ bypassed), better than 0.009% (EQ engaged)
Noise Floor (EQ bypassed)	Better than -102 dBV (unweighted, 22 Hz-22 kHz)
Low Frequency EQ	Corner/center frequencies: 35, 60, 100, 220 Hz; boost/cut ±15 dB; selectable shelf or peak
Mid Frequency EQ	Center frequencies: 200, 350, 700, 1.5k, 3k, 6k Hz; boost/cut ±15 dB; proportional Q; selectable Hi Q (Q ~3.5 at max boost)
High Frequency EQ	Corner/center frequencies: 8k or 16k Hz; boost/cut ±15 dB; selectable shelf or peak
High Pass Filter	Fixed 80 Hz, 12 dB/octave slope; engage switch with green LED
EQ In Switch	Engages all EQ bands except HPF; green LED indicator
Input / Output	Transformer coupled, balanced, ground-free output
Construction	Discrete class-A gain blocks, custom transformers and inductors, low-feedback design
Safety Compliance	Do not operate near water; clean with dry cloth; unplug during storms; refer servicing to qualified personnel
Maintenance	Clean exterior with dry cloth; no user-serviceable parts inside
Warranty	1 year limited warranty on materials and workmanship from date of purchase

Frequently Asked Questions - 551 Rupert Neve Designs

What is the Rupert Neve Designs 551?

The 551 is a 500 Series Inductor EQ featuring three bands of equalization inspired by classic Rupert Neve designs, with custom transformers and class-A gain blocks.

How many EQ bands does the 551 have?

It has three bands: Low Frequency (shelf/peak, selectable at 35, 60, 100, 220 Hz), Mid Frequency (parametric with 6 center frequencies and proportional Q), and High Frequency (shelf/peak, selectable at 8 kHz or 16 kHz).

Does the 551 have a high pass filter?

Yes, it includes a fixed 80 Hz high pass filter with a 12 dB/octave slope, engageable via a front panel switch with green LED.

What power supply does the 551 require?

The module is powered by a 500 series rack providing +/- 16 VDC, drawing 120 mA on the +16V rail and 110 mA on the -16V rail.

Can I use the low band as a peak filter?

Yes, the LO PEAK switch toggles the low band between shelf and peak modes, allowing both gentle slope and bell-shaped EQ curves.

What is the 'Mid Hi Q' switch for?

The MID HI Q switch narrows the bandwidth (increases Q) of the mid band from about 2 to approximately 3.5 at maximum boost, useful for surgical frequency adjustments.

How do I clean the 551?

Clean the exterior with a dry cloth. Do not use any liquids or cleaners. Avoid operating near water or moisture.

Is the 551 transformer coupled?

Yes, both input and output are transformer coupled, with a balanced, ground-free output to minimize hum and RF interference.

What is the warranty period?

Rupert Neve Designs offers a 1-year limited warranty from the date of purchase, covering defects in materials and workmanship.

Where can I get service or support?

Contact Rupert Neve Designs at [e-mail] or call [phone] for troubleshooting and return authorization. Do not attempt internal repairs.

USER MANUAL 551 Rupert Neve Designs

500 Series Inductor EQ

Serial #: □□□□□□□

By:

Operations Manual

551: 500 Series Inductor EQ

Thank you for your purchase of the 551 Inductor EQ. Everyone at Rupert Neve Designs hopes you enjoy using this tool as much as we have enjoyed designing and building it. Please take note of the following list of safety concerns and power requirements before the use of this product.

Safety

It's usual to provide a list of "do's and don'ts" under this heading but mostly these amount to common sense issues. However here are some reminders:

Don't operate your 551 module in or around water! Electronic equipment and liquids are not good friends. If any liquid is spilled such as soda, coffee, alcoholic or other drink, the sugars and acids will have a very detrimental effect. Sugar crystals act like little rectifiers and can produce noise (crackles, etc.). SWITCH OFF POWER IMMEDIATELY because once current starts to flow, the mixture hardens, can get very hot (burnt toffee!) and cause permanent and costly damage. Please contact support as soon as possible at [e-mail] for resolution.

Safety Instructions:

1) Read these instructions.

2) Keep these instructions.

3) Heed all warnings.

4) Follow all instructions.

5) Do not use this apparatus near water.

6) Clean only with dry cloth.

7) Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.

8) Do not install near any heat source such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.

9) Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding type plug has two blades and a third grounding prong. The wide blade or the third prong are provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet.

10) Protect the power cord from being walked on or pinched, particularly at plugs convenience receptacles and the point where they exit from the apparatus.

11) Only use attachments/accessories specified by the manufacturer.

12) Unplug this apparatus during lightning storms or when unused for long periods of time.

13) Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been damaged in any way, such as when power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been dropped.

14) Do not expose this apparatus to rain or moisture.

15) The apparatus shall be connected to a mains socket outlet with a protective earthing connection.

551: Front Panel

High Frequency Shelf / Peak

Selectable at 8 and 16 Khz. With continuous gain from -15 to +15dB. Selectable peak or shelf curves

EQ IN

Engages EQ. Illuminates green when active

Mid Parametric

Selectable at 200, 350, 700, 1.5 K, 3 K, and 6 KHz. With continuous gain from -15 to +15dB. Selectable Hi Q

Low Frequency EQ

Selectable at 35, 60, 100, and 220 Hz. Continuous gain from -15 to +15dB. Selectable peak or shelf curves

HPF

Engages 80Hz HPF. Illuminates green when active

551: Block Diagram

graph LR
    A["INPUT STAGE"] --> B["HPF ENGAGE"]
    B --> C["MID EQ"]
    C --> D["HI & LO SHELVES"]
    D --> E["OUTPUT STAGE"]

    subgraph Inputs
        F["NPPT UMT SPECTR1"] --> G["+"]
        G --> H["HPF (80Hz)"]
        H --> I["+"]
    end

    subgraph Outputs
        J["OUT PUT STAGE"] --> K["+"]
        K --> L["OUTPUT THI SHORET"]
    end

    M["Q/Q"] --> N["HP H/C"]
    O["Q/Q"] --> P["HD P/B"]
    Q["Q/Q"] --> R["200kΩ"]
    S["Q/Q"] --> T["300kΩ"]
    U["Q/Q"] --> V["500kΩ"]
    W["Q/Q"] --> X["700kΩ"]
    Y["Q/Q"] --> Z["900kΩ"]
    AA["Q/Q"] --> AB["100kΩ"]
    AC["Q/Q"] --> AD["120kΩ"]
    AE["Q/Q"] --> AF["150kΩ"]
    AG["Q/Q"] --> AH["180kΩ"]
    AI["Q/Q"] --> AJ["200kΩ"]
    AK["Q/Q"] --> AL["220kΩ"]
    AM["Q/Q"] --> AN["250kΩ"]
    AO["Q/Q"] --> AP["300kΩ"]
    AQ["Q/Q"] --> AR["350kΩ"]
    AS["Q/Q"] --> AT["400kΩ"]
    AU["Q/Q"] --> AV["450kΩ"]
    AW["Q/Q"] --> AX["500kΩ"]
    AY["INP UT STAGE"] --> AZ["-"]
    BA["HPI ENGAGE"] --> BB["-"]
    BC["MID EQ"] --> BD["-"]
    BE["HI & LO SHELVES"] --> BF["-"]
    BG["OUTPUT STAGE"] --> BH["+"]

551 Design Notes

Featuring 3 bands of EQ inspired by Mr. Neve's most prized vintage designs, along with custom transformers and class-A gain blocks, the 551 brings the thick, powerful lows and sweet highs of Rupert's classic EQs to the 500-Series format.

The 551 echoes the simple and definitive Rupert's classic 3-band EQ feature-set, with a custom inductor, switched frequencies and a HPF. Traditional transformer coupled inputs and outputs designed specifically for the 500 series are used for both technical performance reasons and optimum musical reproduction.

The 3-band, custom-tapped inductor EQ on the 551 was inspired by RND's favorite portions of Rupert's vintage EQ designs. The low frequency band is designed to produce a creamy, resonant bass response. Additionally, the LF band on the 551 can be used as either a shelf or a peak filter, adding punch, dimension, and immense control to your low end. The 551's inductor midrange band is also based off of his classic EQs, which are ideal for sweetening vocals and instruments while bringing them forward in a mix. Additionally, the mid frequency band's proportional "Q" response makes it well-suited for minimizing problematic frequencies in a source. The 551's high frequency band is a hybrid vintage / modern design, blending inductor circuitry with capacitor-based topologies to achieve the vintage tones with enhanced control. The High Pass filter is a 12dB/octave design with a fixed 80Hz frequency. As Rupert originally intended with his 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. The EQ circuit itself, however, is a decidedly modern updated design using techniques and components that were simply not available 35 years ago, and should not be considered a "clone".

Both the high and low band can be switched from shelf to peak curves and offer 15 dB of boost or cut. The high band can be switched from 8 kHz to 16 kHz, and the low band can be selected at 35 Hz, 60 Hz, 100 Hz or 220 Hz. The inductor based Mid Band offers 6 center frequencies; 200 Hz, 350 Hz, 700 Hz, 1.5 kHz, 3 kHz and 6 kHz. The Mid Band also has a “Mid Hi Q” switch to narrow the bandwidth (increase the Q) of the filter.

Power and audio connectivity can be supplied through any 500 series compatible rack.

551 Features

EQ IN

Engages all bands of the equalizer except the hpf.

HF

Adjusts up to 15 dB of boost or cut at selected high frequencies.

8K /16K

With the switch out, the center or corner frequency of the high band is 8 kHz. With the button pressed, the center or corner frequency changes to 16 kHz. Between this switch and the HI PEAK switch, you have 4 different EQ curves to finesse the high frequency content.

HI PEAK

When the button is out, the high frequency band operates in shelf mode, boosting or cutting above the corner frequency at approximately 6 dB/octave. Below the corner frequency the amount of boost or cut gradually diminishes. With the HI PEAK button pressed, the high frequency band changes to peak mode with a bell shaped boost or cut curve. The Peak mode utilizes an inductor and capacitor circuit to create the bell-shaped curve.

MID FREQ

The MID FREQ rotary switch has 6 positions to select the center frequency of the mid band EQ stage. This circuit utilizes an inductor and capacitors to shape the EQ curve, the same way as Rupert Neve's console designs of the 70's. The frequencies chosen are 200 Hz, 350 Hz, 700 Hz, 1.5kHz, 3 kHz and 6 kHz. 200 Hz is especially useful for cuts on individual tracks within a dense mix.

MID HI Q

The resonance or Q of the mid band at maximum boost is typically 2 when the button is out. When the MID HI Q is pressed at maximum boost, the Q narrows to approximately 3.5. The Q widens nicely with less boost or cut as is typical for passive EQ circuits. The Q tends to be slightly wider when the frequency is set lower, and slightly higher for higher frequency selections. The Q is also narrower for cuts than it is for boosts and the mid band is non-symmetrical by design.

MID LEVEL

Adjusts up to 15 dB of boost or cut at the selected mid frequencies. Remember to reduce the signal level at the source to minimize the potential for distortion when any of the 3 bands are boosted significantly.

HPF

Engages an 12dB per octave High Pass Filter set to 80Hz

LOW FREQ

The LOW FREQ rotary switch has 4 positions for selecting one of four corner or center frequencies for the low band EQ section. The frequencies are 35 Hz, 60 Hz, 100 Hz and 220 Hz.

LO PEAK

When the button is out, the low frequency band operates in shelf mode, boosting or cutting below the corner frequency. Above the corner frequency the amount of boost or cut gradually diminishes at approximately 6 dB/octave. With the LO PEAK button pressed the low frequency band changes to peak mode with a bell shaped boost or cut curve.

LF

Adjusts up to 15 dB of boost or cut at the selected low frequencies. Cut can be used as a variable, and perhaps more gentle alternative to using the HPF.

OUTPUT

The main output signal comes from the output transformer secondary which is balanced and ground free. A ground free connection guarantees freedom from hum and radio frequency interference when connected to a balanced destination.

POWER

+/- 16V supplied by 500 series rack

Specifications

Equalizer Bypassed

Noise:

Measured at Main Output, un-weighted, 22Hz-22kHz, source impedance 40 Ohms balanced.

Better than -102dBV

Frequency Response

Main output, no load +/- 0.1dBu from 20Hz to 31.5kHz

-1dB @ 120kHz

Maximum Output Level 23.25dBu

Total Harmonic Distortion and Noise

@ 1kHz, +20dBu output level, no load. Better than 0.0025%

@ 20Hz, +20dBu output level, no load. 0.13% Typical (2nd and

3rd harmonic)

High Pass Filter: -2.7dB @ 80Hz

Slope: 12dB/Octave

Equalizer Engaged

Noise:

Measured at Main Output, un-weighted, 22Hz-22kHz, source impedance 40 Ohms balanced.

Better than -94dBV

Frequency Response

Main output, no load +/- 0.25dBu from 20Hz to 45kHz

-2dB @ 120kHz

Maximum Output Level 23dBu

Total Harmonic Distortion and Noise

@ 1kHz, +20dBu output level, no load. Better than 0.009%

@ 20Hz, +20dBu output level, no load. 0.13% Typical (2nd and 3rd harmonic)

Power Requirements

120mA on +16VDC

110ma on -16VDC

Low Frequency EQ

Mid Band EQ

High Frequency EQ

PRODUCT WARRANTY

Rupert Neve Designs warrants this product to be free from defects in materials and workmanship for a period of one (1) year from date of purchase, and agrees to remedy any defect identified within such one year period by, at our option, repairing or replacing the product.

LIMITATIONS AND EXCLUSIONS

This warranty, and any other express or implied warranty, does not apply to any product which has been improperly installed, subjected to usage for which the product was not designed, misused or abused, damaged during shipping, damaged by any dry cell battery, or which has been altered or modified in any way. This warranty is extended to the original end user purchaser only. A purchase receipt or other satisfactory proof of date of original purchase is required before any warranty service will be performed. THIS EXPRESS, LIMITED WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, TO THE EXTEND ALLOWED UNDER APPLICABLE STATE LAW. IN NO EVENT SHALL RUPERT NEVE DESIGNS BE LIABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OF THIS PRODUCT. Some states do not allow the exclusion or limitation of consequential damages or limitations on how long an implied warranty lasts, so this exclusion may not apply to you.

WARRANTY SERVICE

If you suspect a defect in this product, please call us at 512-847-3013 or email us at [e-mail] to discuss the suggested defect (it is possible that a suspected defect could be due to improper usage) and to obtain a return authorization number. It shall be your responsibility to pay for shipping the product to us, and, if the product is determined to be defective, our responsibility to pay for shipping the product back to you.

Rupert Neve Designs

PO Box 1969

Wimberley TX 78676

www.rupertneve.com

tel: [phone]

fax: [phone]

551 Manual Rev-A2 Part # 775-00018