The Shelford Diode Bridge Compressor -- also known as the 5254 -- is two channels of iconic diode bridge compression, thoughtfully improved and refined for modern tracking, mixing, and mastering. The rich tonality of the Shelford Compressor can produce a wide range of colors -- helping you make a statement with your music. This compressor is outfitted for dual mono or stereo use with Rupert Neve Designs' custom transformers and class-A electronics in a compact 1U 19" enclosure.

Since the early 1970s, Rupert Neve's vintage 2254 and 33609 diode bridge compressors have been revered for the punch & thickness they bring to drums, instruments, and the mix bus. Originally developed for the acclaimed Shelford Channel, the Shelford Diode Bridge Compressor captures the soul of these coveted compressors while providing a host of modern updates, including advanced timing control, significantly lower noise, fully stepped controls throughout, higher voltage power rails, and internal parallel processing capabilities.

Fifty years after Mr. Rupert Neve created his first compressor designs, the Shelford Diode Bridge Compressor reimagines the larger-than-life personality of these classic circuits with new levels of precision and control, enhanced creative power, and increased punch for your tracks, mixes, and masters.

The Diode Bridge

Diode bridge compressors are known for being able to push key sources like vocals, electric guitars, bass and drums to the forefront of a mix. By first… read more identifying certain limitations of the vintage units like the legendary 2254 and 33609, considerable effort was made to reproduce the unique tone of these classics while enhancing flexibility for the modern age. These include improving the noise floor & accuracy, expanding inflexible time constants, adding full wave sidechain detection for improved dynamic response, and widening the range of threshold and ratio controls.

Timing is Everything

The unified TIMING control consists of six selectable settings, carefully chosen for different applications -- a major upgrade from the slow, fixed attack of the vintage units. FAST and MF settings are designed to help clamp down on more transient signals like drums, plucked string instruments and fast vocals. MED and MS have slightly slower attacks and releases which allow more transients through, while having a slightly longer recovery. Lastly, SLOW and AUTO are both significantly slower and feature complex nonlinear release times, with smoother, less audible level control.

FAST mode increases the speed of both the attack and release for each setting, effectively doubling the number of time constants from 6 to 12.

In general, faster TIMING settings will introduce more harmonic content and slower TIMING settings will have a slight reduction in harmonic content, resulting in more transparent compression. Due to the nature of this circuit topology, these time constants inherently adapt themselves slightly, depending on several factors: compression ratio, threshold, and source material. These subtle timing shifts and varying harmonic content give the Shelford Diode Bridge Compressor a unique & colorful personality.

The Right Blend

The BLEND control allows the user to inject smaller amounts of extreme compression into an otherwise unaffected signal, creating an enhanced yet natural sound that maintains dynamic range with blendable color and punch.

Take Control

In addition to the TIMING control, the compressor can be further manipulated by the RATIO, THRESHOLD, GAIN, S/C HPF, S/C INSERT and LINK controls. The RATIO control has six selectable positions on the rotary switch and allows the user to set the slope of the compressor curve with ratios of 1.5:1 through 8:1. The THRESHOLD control allows the user to adjust the point at which compression begins, ranging from -25dBu to +20dBu. The GAIN control adds make-up gain ranging from -6dB to +20dB. The S/C HPF is 12dB/octave with continuously variable frequency control from 20Hz to 250Hz. This feature can be immensely useful for making the compressor respond less to the powerful -- and often more sustaining -- low frequencies in a mix or instrument, which might otherwise give the compressor a more "mushy" response and eat up internal headroom faster. The SC INSERT is comprised of an always-active send and return for the compressor side chain, which can be used to insert a more fine-tunable EQ to further sculpt the compressor response, or as a way to insert a key signal into the return, controlling the compression via a separate source to "duck" the signal when the key source is above the threshold. LINK engages a function that links the THRESHOLD setting of both channel's compression circuits; whichever channel is applying the most gain reduction becomes the master control.

A Note on The Name

For those of you who are interested: this two-channel unit was first released in October 2020 as the "5254 Dual Diode Bridge Compressor." In 2024, Rupert Neve Designs updated the name to "Shelford Diode Bridge Compressor" to better reflect the circuit's origins. But aside from the name change on the faceplate, the rest of the unit -- inside and out -- is identical to the 5254 many of you already know and love.

Features:

- Classic Diode Bridge Tone: Capture the punchy, larger-than-life tone used on countless hit records for the last 50 years.
- Advanced timing controls: Custom-shape your compression envelope with the unified timing control, which enables a much wider range of responses than vintage units or clones.
- Custom Transformers and Class-A Line Amplifiers: Vintage warmth meets the improved headroom and precision of Rupert Neve's updated transformer-coupled line stages.
- 31-Position Detented Controls: Accurately recall and match your settings with precision and speed.
- Built-In Parallel Compression: Internal blend control enables you to subtly dial in more dramatic compression settings as desired.
- Full-Wave Sidechain Detection: Enhanced from the vintage units' half-wave design, the updated sidechain detector provides more accuracy.
- Stereo Linking: Run your compressors in either dual mono or stereo configurations.
- Internal Universal Power Supply: EIC connection for world-wide AC power from 90-240V embedded in the 1U rack-mountable chassis.

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