Rupert Neve Designs: 5254 Dual Diode Bridge Compressor

Over the past two decades, Rupert Neve Designs has been known in the recording community as a company that creates and builds a wide variety of high-quality pro audio equipment found in studios worldwide. I have used many of their units and always felt they sounded excellent, so I was excited to have the opportunity to audition their 5254 Dual Diode Bridge Compressor. The 5254 was designed by the engineering team at Rupert Neve Designs, inspired by the classic Neve 2254 and 33609 diode bridge compressors of the past. However, rather than clone an old circuit with limitations, they have created an all-new compressor with greatly expanded features that is every bit as good sonically as its famous predecessors, yet much more versatile and powerful.

At first glance, I was immediately impressed by the single rack space unit’s classy appearance and robust build. The Shelford blue color and backlit VU meters give it an old-school vibe that looks great in the rack. All the pots and switches feel sturdy, and the layout is simple. Each channel features fully detented Threshold and Gain pots, six position switches for Ratio and Timing, plus two of my favorite features: the Blend knob and the SC/HPF control. Additionally, there is a stereo link switch, a compressor bypass, SC/HPF bypass, a switch that allows the meters to toggle between gain reduction and output level, and a Fast switch. This unit is clearly built to exceptionally high standards.

Before I discuss my experiences using the 5254, I’d like to touch on diode bridge compressors and how they function to create their unique sound. I spoke with the team at Rupert Neve Designs about the technical aspects of how this compressor works, and here’s what they said: “Diode bridges are commonly used to rectify AC to DC by allowing current to flow in one direction only. However, when biased correctly, a diode bridge can also be used to carefully control voltages that will then apply the desired amount of gain reduction. As the bias voltage is increased in the control path, the proper amount of attenuation will be applied in the audio path. Our custom transformers, combined with the unique non-linearity of diodes, produce pleasing harmonics as level is increased into the diode bridge itself – resulting in a lush, warm, and rich tonality. The harder the 5254 is driven, the more harmonics are produced. This can create plenty of tone and character before even applying compression, if desired.” In other words, this compressor has a lot of color and character, which becomes more audible the harder one pushes it.

How does it sound? First, I ran tones through it to see how tightly matched the two channels were in terms of Gain and Threshold. To my delight, the L/R matching was virtually perfect at all settings. The fully-detented pots make recalling settings simple – getting the two channels to match is quick and easy work. I also noticed that the noise floor is much lower than other diode bridge compressors I have used – the 5254 is about 20 dB quieter than a vintage 2254! My initial audio tests involved running finished mixes through the 5254 to see how it would respond to full program material. Immediately, I was struck by the tone, regardless of whether or not compression was happening. The 5254 has a gorgeous, silky top end and a punchy, thick low end that I have come to associate with equipment designed by Rupert Neve. It’s a quite colorful box, and what a lovely color it is! The compression can be subtly transparent or very aggressive, and it performs both tasks in an equally musical manner. Six time constants cover a wide range of Attack and Release settings – the Fast switch increases the speed of the selected timing by 70%, giving the user 12 total timing settings. This means the 5254 can be lightning fast or syrupy slow, and everything in between. At its fastest setting, the Attack is 250 μs, and the Release is 100 ms, while at its slowest setting, the Attack is 80 ms, and the Release is 1.5 seconds. In practice, this means that the compressor is an incredibly versatile tool for shaping audio. What really impressed me was how much I could control the compression by using all the different features. For example, the variable SC/HPF can solve the problem of a big low end causing the compressor to overreact. While many compressors have a switch that inserts a fixed high-pass filter into the sidechain, the 5254 allows for continuously variable sweeping of its high-pass filter from 20 Hz to 250 Hz. This allows the user to very specifically sculpt the low end that is triggering the compressor. I particularly enjoy using this on bass guitar, or bass-heavy mixes that need compression while retaining low end. Parallel compression (wet/dry) is controlled with the Blend knob, a feature I wish more compressors offered. As it implies, this knob allows the user to blend the compressed signal with the uncompressed signal. I found it helpful on a wide variety of sources, especially full mixes, acoustic guitar, and vocals. Changing the ratio also affects the behavior of the compressor more than most units I have used – auditioning all the different ratio settings is worth the effort. I feel that users should not overly pay attention to any of the numbers associated with the settings on the 5254 but rather just play around and use their ears – this unit is highly interactive and musical.

After a few days of running many different sources through the 5254, my conclusion is that it imparts a silky-sweet tone on everything. Vocals, guitars, bass, drums, percussion, busses, and full mixes all sound enhanced running through the transformer-balanced diode bridge circuit, and the compression timing settings can cover a lot more ground than one might assume. It has all the fabulous tone and character of the old-school diode bridge compressors, with a much lower noise floor and far greater control options. The 5254 is a unique-sounding modern classic that stands out to me as one of the most sonically pleasing, versatile new compressors I have heard in many years.