The Rupert Neve Designs Shelford 535 is a single-channel 500 series compressor inspired by the same diode bridge principles in the classic 2254. 

Overview

The Rupert Neve Designs Shelford 535 takes the soul of the legendary 2254 and updates it for modern requirements. It offers the larger-than-life compression of its ancestor and the precision and flexibility required by current workflows. 

Originally designed for the Shelford channel, the 535 has been adapted for the 500 series format and includes a custom transformer designed by Rupert Neve and a Class A output amplifier.

The Rupert Neve Designs 535 offers quick and easy settings with a six selectable ratio ranging between 1.5:1 through 8:1, easily accessible via the rotary switch. 

The 31-step Threshold control ranges from -25dBu up to +20dBu. The Gain control offers gain compensation between -6dB and +20dB, accessible through its 31-step switch.

A fixed 150Hz, 12dB/octa side-chain filter is also provided, allowing the compressor to respond less to powerful bass content avoiding unwanted triggering caused by low frequencies and keeping the compression clear.

Diode Bridge Compression

Diode Bridge compression works by using a diode’s non-linear properties to control the gain reduction.

Diode Bridge Compression was Rupert Neve’s way of creating a colourful, weighty, punchy compressor before the advent of VCAs. Unlike VCA compression, which is usually thought of as bringing clarity, the diode bridge provides a weighty and harmonically rich tone, effortlessly bringing the source forward in the mix.

Circumventing the natural distortion levels of diodes by configuring them in a bridge format, Rupert Neve originally came up with the 2252 compressor, which then evolved into the revered 2254.

The Rupert Neve Designs 535 has been meticulously designed to recreate the unique tone of the 2254 but with a much-improved noise floor. They are particularly well suited for bringing vocals, electric guitars, bass and drums at the front of the mix. 

Flexible Timing

The 535 compressor includes six selectable Timing settings that control both the attack and release times simultaneously. Each of these settings has been carefully chosen for different applications. 

FAST: Fast Attack (750µs), Fast Release (130ms)
MF: Medium Attack (2.25ms), Fast Release (130ms)
MED: Medium Attack (2.25ms), Medium Release (400ms)
MS: Medium Attack (4ms), Slow Release (725ms)
SLOW: Slow Attack (10ms), Slow Release (1s)
AUTO: Medium Attack (5ms), Dual-decay Release (T1 500ms, T2 1s)

FAST and MF settings are ideal for clamping down on transient rich material like drums or acoustic guitars. MED and MS settings offer slower reactions (slower attack and release times) for vocals and guitars, while the Slow and AUTO provide smoother level control.

A FAST mode dramatically increases the speed of both attacks and release times for each setting, increasing the number of time constants from six to 12. Faster modes will also increase harmonic distortion, adding noticeable colouration to the sound. Slower modes will result in more transparent compression.

The attack and release on diode bridge compressors vary slightly depending on the ratio, threshold and incoming audio, resulting in dynamically shifting timing and harmonic content. It is an integral part of the diode bridge compressor’s sound.

A Flexible Compressor 

The Shelford 535’s obvious colouration might prove too much on some occasions, and, as a result, it includes a Blend control which lets you dial in the amount of compression to your dry, unprocessed signal. This feature might be desirable to reinject some transients lost in fast settings while retaining some of the character and punch of the compression, or simply creating a natural sound with controlled dynamics. 

Two 535 can be used together for stereo operations thanks to the included LINK button if your 500- series rack features a link control. It sends a control voltage via a Sidechain input to trigger both units equally at the incoming audio.