Throughout his illustrious career, Rupert Neve continued to refine the diode‑bridge compressor design he first created over half a century ago.
Few admirers of the late, great Rupert Neve can be unaware of the original Neve 2254 diode‑bridge compressor, introduced in 1969. It became a standard module in Neve’s 80‑series consoles, quickly gaining a reputation for its ability to glue mixes together nicely and also to add punch and colour to individual sources. The core design was also employed in later consoles and standalone dynamics products. Homages and variants of this ingenious design have appeared ever since, some staying faithful to the original circuitry (and its inherent compromises), and others featuring redesigned elements to improve the technical performance. AMS Neve, for example, issued a 2254 recreation which we reviewed back in August 2009.
So it’s not surprising that, 50 years on, Rupert Neve Designs have introduced an updated diode‑bridge compressor of their own. Initially, this appeared as the dynamics section of the Shelford Channel outboard unit but it was subsequently re‑engineered in the form of a 500‑series module, the 535, which we reviewed in SOS May 2018. More recently, this same modernised diode‑bridge compressor design has been reborn as a standalone, dual‑channel, rackmounting version. Called the 5254, it sits within the company’s Shelford range.
The 5254 has a nicely understated aesthetic, with the familiar dark blue/grey paintwork and elegantly slim colour‑coded control knobs, along with a pair of rectangular VU meters in the centre of the panel, each printed with Rupert’s initial. It looks like a serious, classy, no‑nonsense professional device. I haven’t figured out the logic of the control knobs’ colour‑coding, but there are only six per channel, all with clear and familiar legends and markings. Three are blue/grey (HPF, Threshold and Ratio), two are silver/grey (Timing and Blend) and one is red (Gain).
The Ratio and Timing controls are quite ‘heavy’ rotary switches, although I think they feel stiff only because the knob diameter is so small. Ratio provides rates of 1.5, 2, 3, 4, 6, or 8:1, while the side‑chain’s attack and release time‑constants are controlled together with six pre‑defined ‘Timing’ combinations, identified only as Fast, MF, Medium, MS, Slow and Auto. A Fast button reduces both the attack and release values of each setting by around 30 percent, giving the 5254 a significantly faster reaction time than the original design. The selected time constants also vary slightly depending on the ratio and threshold settings, as well as the dynamic nature of the source material itself — this is an effect that contributes to the unique character of the diode‑bridge compressor.
As an overview of all the options, the attack times range between 0.25 and 80 ms, while the release (recovery) times span 0.1 to 2 seconds, and the longest release times follow a non‑linear curve, which gives a very smooth removal of gain reduction.
The 5254’s auto‑recovery system is a conventional two‑stage release, responding to loud transients with a fast release time of 400‑900 ms, switching to a slower 1‑2 second release curve as the gain reduction diminishes. This arrangement maintains the impression of loudness for transients, while minimising background pumping side‑effects.
The Threshold knob has...