We cast our eyes and ears over Mr Neve’s elegant contributions to the 500-series format.
While we’ve looked at several Rupert Neve Designs (RND) products over the years, we’ve not yet had a close look at any of their 500-series gear — so when they recently added the 535 diode-bridge compressor and a new 500-series PSU/chassis to their range, we took the opportunity to evaluate the whole of their modular range.
I’ve discussed the two chassis options in the ‘On The Rack’ box later, so I can dive straight in to a discussion of the various modules. The current crop includes two preamps (the 511 mic pre with Silk Texture, and 517 mic pre with DI and compressor), and two dedicated compressors (the new 535 diode-bridge, and 543 VCA model), along with the 551 three-band inductor EQ, and the 542 Tape Emulator. For this review, I received an R10 rack along with pairs of all of these modules apart from the 517 mic pre/DI.
Most modules feature the familiar RND light-blue-grey colour scheme, and are derived from other RND Portico units, while the dark-grey front panels of the new 535 diode-bridge compressor and 551 inductor EQ denote their design origins in the company’s Shelford range (reviewed by Bob Thomas in SOS August 2015: www.soundonsound.com/reviews/rupert-neve-designs-shelford-5051-5052). But while all these modules are derived from other products, the detailed amplifier circuitry and transformers have been redesigned to work with the lower-voltage power rails and supply current limitations of the 500-series format. The RND engineers have gone to great lengths to match the technical performance and sound qualities as closely as possible, and claim the only real difference is a very slightly reduced headroom margin — we’re talking about only 3dB here, and typically +22dBu instead of +25dBu, so it’s really nothing to worry about!
The 511 preamp draws heavily on the Portico 5012 design (reviewed back in SOS April 2007), and construction is to very high standards. In fact, I wish all 500-series modules were built this well! Unlike many 500-series modules, all RND’s offerings are fully enclosed, with a steel case effectively incorporating a sub-frame to support the securing nuts for the rotary controls, which keeps the mechanics hidden behind the front-panel. As a result, the module’s attractive anodised, slim-line, aluminium knobs sit flush on the panel, and the buttons poke through holes, which all combines to create a smart and uncluttered appearance.
Another nice engineering touch is that the module’s edge connector is a separate PCB bolted onto the main circuit board. This affords some extra internal height for components such as transformers and capacitors, but also allows easy replacement of the edge connector should it become damaged or worn. Surface-mount components are used on the two internal circuit boards, and I spotted several 5534 op-amps as well as some discrete transistors, along with several high-quality through-hole electrolytic capacitors and a compact output transformer. The whole mechanical design is very neat and classy, both technically and aesthetically.
Preamp gain is selected with a 12-position rotary switch (0 to 66 dB, in 6dB steps), while a ±6dB rotary trim control (with centre-detent) takes the maximum gain up to 72dB, while also allowing precise gain matching for stereo applications. Another rotary control adjusts the turnover frequency of a second-order (12dB/octave) high-pass filter (20-250 Hz), while a fourth determines the amount of Silk Texture, of which more in a moment. Four illuminated buttons engage phantom power, polarity inversion, the high-pass filter, and the Silk feature, while an LED at the top of the panel illuminates when the module is receiving power. An eight-LED bar-graph meter, scaled from -10 to +22 dBu, displays the output level, although note that the meter shows the signal level before the output transformer, so strong Silk Texture settings can result in slightly higher levels than are displayed.
The preamp circuit design is based on Rupert Neve’s well-proven ‘transformer-like’ (TLA) instrumentation-amp configuration, which boasts a 150kHz bandwidth, an EIN of -125dB and an unusually high 10kΩ input impedance, the last favoured by Rupert Neve as it minimises the microphone loading and gives a flatter response while helping to preserve transients. This was the only module in the review rack with no input transformer, and there’s also no input pad because, impressively, when set to 0dB gain the input stage can accommodate line inputs up to +22dBu.
The Silk facility is based on the company’s ‘Red Silk’ circuit. The idea is to emulate the sound character associated with Neve’s early discrete Class-A transformer-coupled designs. Essentially, the Texture control reduces the amount of negative feedback around the output driver which is derived from one of the output transformer’s two secondary windings. The effect is to introduce a rising high-end response, along with increasing the second-harmonic distortion in the mid- and high-frequencies due to transformer saturation. The strength of the Silk processing can be adjusted from barely audible to very obvious — the Texture control’s range is considerably greater than that in the original Portico II. I found that mid-range settings added a tasteful and attractive vintage character.
The floating (ground-free) transformer-balanced output means the signal level remains unchanged whether the destination is balanced or unbalanced, and there’s minimal risk of ground-loops. The maximum output level is a healthy +23dBu, and the module draws a modest 100mA.
With Silk switched off, I found the 511 preamp to fundamentally give a very clean and neutral sound with masses of quiet gain. The switched gain control completely avoids the common problem of gain-bunching at the loud end, while the Trim knob still allows precise level matching when necessary — it’s the traditional professional approach and it works very nicely indeed. The variable high-pass filter is very welcome, as it’s always a good idea to remove unwanted low end as early as possible in the signal chain. For many, though, the real star facility will be that Silk mode, which completely changes the character of this preamp to lend it a sparkling and, dare I say, ‘silky’ top end. It really is very nice!
The 551 is a simple three-band, inductor-based EQ which builds on the topologies and sound characters of Neve’s vintage designs, using a custom-wound multi-tap inductor and more modern technology for the discrete gain stages and the occasional buffering op-amp.
Illuminated buttons switch the entire EQ section into circuit, and select the fixed (80Hz) second-order, high-pass filter, and an LED at the top lights when power is being received — the unit draws 120mA from the positive rail and a little less from the negative rail.
The high and low EQ bands can be switched independently between shelf and peak (bell) modes, with selectable corner/centre frequencies. A white button switches between 8 and 16 kHz for the high band, while the low band’s more comprehensive options are designated on a rotary switch (35, 60, 100 or 120 Hz). Another rotary switch sets the mid band’s centre frequency (200, 350, 700, 1500, 3000 or 6000 Hz), while a white button engages a ‘High-Q’ mode.
As standard, the mid band has a Q of 2 (0.7 octaves), but pressing the button raises the Q to around 3.5 (0.4 octaves), making the filter sharper and more selective. In practice, it’s not quite as clear cut as that sounds, because the Q varies with the amount of boost or cut and the filter curves are asymmetrical, with the bell curves being narrower when cutting than boosting. This apparently complicated behaviour translates into a very natural-sounding equaliser which is very intuitive; gentle boosts or cuts affect a relatively wide range of frequencies for a subtle shaping effect, but the filters become more selective and precise in high boosts or cuts in exactly the right way.
The 551 is transformer-balanced in and out, and this brings a useful side-benefit of allowing the unit to add a little analogue flavour when the EQ section is bypassed through the transformers and buffer amps. In terms of technical performance, the 551 accepts and delivers a maximum signal level of slightly more than +23dBu, with very low distortion (0.006 percent) and an acceptable noise floor of -84dBu (this was slightly higher than the published specifications).
Based on the Portico 5043 (reviewed in SOS July 2007), this mono VCA compressor can also serve as a ‘brick-wall’ limiter thanks to a ratio control which offers ratios from 1.1:1 up to 40:1, all with a nice soft-knee characteristic. It also features a configurable sidechain, with selectable feed-back or feed-forward modes, as well as selectable RMS or ‘hybrid-peak’ detection options. The over-riding ethos of this compressor is transparency, and it is clean-sounding almost to the point of aural invisibility — unlike the 535 diode-bridge compressor, as discussed below.
Oddly, the power LED featured on all of RND’s other 500-series is absent from the 543, but it is otherwise styled in the same manner. As you might expect, the VCA circuitry is based around a THAT 2181 chip working in collaboration with a THAT 4305 ‘dynamics processor’ in the side-chain, all buffered with a handful of TLO72 op-amps. Test bench measurements showed the 543’s distortion (THD) figure to be around 0.09 percent and the noise floor was a healthy -94dBu. The maximum output level measured slightly lower than the other 500-series modules (about +21dBu), but that’s not going to cause any problems in practice given that the role of a compressor is to turn loud things down! The current consumption is around 125mA.
An unexpected feature is the provision of two connection pins accessed through a hole in the rear panel above the edge connector. These offer an alternative method of linking the sidechain to that of other modules for stereo operation. The reason for this facility is twofold: first, a few 500-series racks don’t include the standard link-bus provision and, second, the racks that do provide this link bus normally share it across all of the modules in the rack (discussed further in the ‘On The Rack’ box). In either case, RND’s additional link-bus connections could be very helpful.
Five front-panel rotary controls adjust the threshold (-30 to +20 dBu), ratio (1.1:1 to 40:1), attack time (20-75 ms), release time (100ms to 2.5 seconds), and make-up gain (-6 to +20 dB). An illuminated button switches the compressor on, while three white buttons engage a high-pass filter in the sidechain, switch between the feed-back and feed-forward modes, and select the RMS or hybrid-peak detection. A recessed toggle switch connects the sidechain to the rack’s link bus (see box), facilitating matched and synchronised gain reduction for stereo/surround operation. Two eight-LED bar-graph meters show the output level (0 to +22 dBu) and gain-reduction 1-22 dB).
The sidechain’s feed-back mode reflects the topology of Rupert Neve’s earliest compressor designs (and most vintage compressors, come to that), where the sidechain signal is derived from the compressor’s output. This configuration tends to produce more transient overshoots than the feed-forward mode, and exhibits much gentler ratios than the control knob setting implies. The reason is basically because the signal is already at the output before the side-chain can sense the level and start applying (or releasing) attenuation. It’s also interesting to note that the shape and speed of the attack and recovery time-constants are different with a feed-back format compared with a feed-forward system, giving this type of configuration a more ‘musical’ and softer sound character. In contrast, the much faster, more modern-sounding feed-forward structure exerts far tighter control over the signal dynamics, and delivers the compression ratios exactly as marked on the control.
I’ve mentioned the RMS (average) and ‘hybrid-peak’ sensing modes, and these are borrowed from the Portico II. The former is intended to control the signal levels in a way that closely matches our perception of loudness, and this would normally be preferred with moderate compression ratios. The hybrid-peak mode combines both peak and RMS weighting, and provides much better control of transients; it is more appropriate when the production emphasis is on preventing overloads or for peak-normalising signals in mastering, particularly when using limiting ratios (10:1 or above).
Activating the switchable high-pass sidechain filter reduces the compressor’s sensitivity below 250Hz, so that the amount of compression is determined mainly by the mid-range programme content, to which the ear is more sensitive. It also avoids the pumping effect which can occur if the gain reduction follows the bass or kick content in a mixed track.
There’s no automatic recovery time but the release control spans a usefully wide range, as does the attack-time control — I was initially concerned to see that the fastest marked attack time was 20ms, but in use it appeared to be fast enough; I suspect RND’s method of measuring or specifying the attack time may differ from that employed by some other manufacturers (there are a couple of different ‘standard approaches’).
In contrast to the 543 VCA compressor, the 535 diode-bridge design is the opposite of transparent; it is intended to deliver a punchy kind of compression which is intentionally ‘vibey’ and characterful. Rupert Neve’s original vintage 2254 diode-bridge compressor, of course, is already famous for introducing such a distinctive sound character, but in designing the new module RND also addressed various inherent technical and operational limitations. Consequently, the new design enjoys considerably more versatility and a much lower noise floor than the vintage 2254, and it features a distinctly different set of controls from most other compressors.
Painted in the same dark grey as the 551 EQ , the 535 diverges from the paradigm of all RND’s other 500-series modules by employing 31-detent actions on three of the rotary controls. The threshold control spans the range from -25 to +20dB, while the ratio is adjusted with a rotary switch between settings of 1.5, 2, 3, 4, 6, and 8:1. Rather than separate attack and release controls, a rotary switch labelled ‘Timing’ selects values for both simultaneously, and this presents the user with six options: Fast, MF, Medium, MS, Slow, and Auto. Usefully, these attack/release timings can be halved by pressing an illuminated ‘Fast’ button, resulting in a total of 12 possible time-constant pairings.
The fastest standard setting provides an attack time of a blindingly quick 0.75ms coupled with a release of 130ms — and both values can be halved via the Fast button if needed. At the other end of the scale, the slowest setting employs a 10ms attack and 1s release. The auto mode uses a moderate 5ms attack and switches between two release curves, initially with a 500ms time constant before reverting to a one-second decay. I found this Auto mode worked extremely well in almost all circumstances and it became my default setting.
Parallel compression can be set up using the Blend control, mixing between the dry source signal and the output of the compression path, while a gain control rounds out the adjustable parameters, with make-up gain ranging from -6 to +20 dB. An illuminated ‘Comp In’ button engages the compression processing, and two further white buttons select the link bus (for stereo working) or a 150Hz sidechain high-pass filter to reduce the compressor’s sensitivity to low-frequency content. As with the 543 compressor, a pair of bar-graph meters shows the output level (-10 to +22 dBu) and gain-reduction (1 to 22 dB), but the 543’s secondary link-bus connector is absent here.
As this compressor’s name implies, its active gain-reduction element is a ‘ring’ or ‘bridge’ arrangement of diodes, with the audio signal applied across one axis of the bridge and the side-chain control signal driving a current across the other axis to vary the amount of signal attenuation. The 535’s sidechain operates in a feed-back configuration and, in this incarnation, employs full-wave rectification to provide lower intermodulation distortion and faster attack times than the original 2254 design. The non-linearity of the diodes results in some inevitable harmonic coloration, with the amount dependent on several factors including how hard the circuit is driven, the selected compression ratio, and the attack and release time constants. Elevated drive levels, stiffer ratios, and faster attack and release times produce noticeably more coloration; and conversely low ratios, slow timing settings, and engaging the sidechain’s high-pass filter all help to make the compressor more transparent and subtle. Using the Blend control for parallel compression also works very well to deliver more subtle compression effects.
Although noticeably cleaner-sounding (at gentle settings) than I remember the 2254 being, the 535 diode-bridge compressor has a distinctly vintage sound character, and it can develop quite an attitude when pushed hard — assisted, no doubt, by the very hard-knee characteristic of its ratio slopes and the fact that the actual compression ratios are rather stiffer than the switch markings suggest at the gentle end of the range (I measured the lowest ratio as 2.4:1 rather than the marked 1.5:1). Consequently, I’d say the 535 diode-bridge compressor is a bit of a ‘Marmite product’ — it probably won’t suit everyone’s requirements, but others will love it, and it is certainly a very useful alternative to the 543 VCA model.
The final module supplied in the review set was the Tape Emulator, derived from the Portico 5042 unit (reviewed in SOS July 2007). This is designed to replicate the effects of recording to analogue tape courtesy of RND’s famous ‘True-Tape’ circuitry, which uses bespoke miniature transformers to replicate the magnetic behaviour of record/play heads in generating third-order harmonics along with some soft-clipping for second-order harmonics at higher levels. The module also features a configurable Silk function for extra tonal flavouring!
The 542 has just four rotary controls, three buttons, and two bar-graph meters. The top control, Trim, essentially adjusts the module’s input sensitivity by up to ±12dB, while the Saturation knob determines the drive level into the tape emulation circuitry, the amount being displayed on an adjacent eight-LED bar-graph meter, scaled one to eight (soft clipping occurs above five).
An illuminated button activates the True-Tape processing, and a white button reflects the sonic influence of different tape speeds by changing pre-emphasis and de-emphasis filter curves around the True-Tape circuit. These alter the amount of HF extension and the low-end ‘head-bump’ frequency and level, with the slow-speed setting (15ips) giving a noticeable HF roll-off (-3dB at 20kHz), along with a bass boost of between 3 and 6dB depending on Saturation level, centred at 60Hz. Switching to the 30ips option the high-end is pristine while the low-frequency head-bump reduces to between 2 and 4 dB, centred at 120Hz. As a result, the 30ips setting is noticeably smoother and more open-sounding.
However, the final strength of this True-Tape processing can be finessed by using the Blend control to mix between the dry source signal and the processed signal, enabling the overall effect to be made very subtle indeed, if required.
Although completely separate in a circuitry sense from its True-Tape processing, the 542’s transformer output stage incorporates RND’s Silk circuitry. I discussed this earlier, but in this incarnation it is switchable between ‘Red’ and ‘Blue’ modes. The controls comprise an illuminated button to toggle between Off, Red and Blue, the illumination changing colour appropriately, and a rotary Texture control to adjust the amount — the control range is again much greater than that found in the original Portico products.
In essence, the Red mode raises the overall level by about 1.5dB and boosts the high end above 5kHz by about 3dB, simultaneously increasing the harmonic content, too. The Blue mode doesn’t affect the high-end significantly (if anything, it introduces a very slight roll-off), but it boosts the low frequencies below 100 Hz, reaching about +1.5dB at 30Hz, while also adding more saturation to the LF and low-mids. Although these two options sound quite different in character, they both create the impression of more ‘vintage’ sound characters — I found them rather addictive!
I mentioned the True-Tape drive meter earlier. A second bar-graph meter at the bottom of the front panel displays the output level (scaled from -10 to +22 dBu), an arrangement which I initially found a little confusing when using the review modules together, since all the other RND modules have their output level meters at the top of the panel. But there’s a good reason for this configuration: it keeps the drive meter alongside the input Trim and Saturation controls at the top of the panel.
My test bench measurements revealed that the 542 can drive output signals to slightly over +23dBu, and the noise floor is a little lower than the other modules tested, at -100dBu. Distortion measurements seem pointless in a device that specifically exists to distort the signal, but for the record I found it possible to dial in as much as three percent THD if required (this rings a bell as a typical reference level value when aligning analogue tape recorders!).
Everything about RND’s 500-series modules and R10 rack impressed me. The mechanical design and build quality are excellent, and it’s clear to see what the premium price is buying. The control knobs are elegant and beautifully machined, and sit well in the fingers in pleasantly uncrowded control panels with clear and precise panel markings. I was a little surprised at the lack of consistency across the range — the different colour schemes, the missing power LED and link-bus connectors, and the one-off use of detented controls, but these things don’t impact on the sound or quality of the modules in any significant way.
The 511 mic preamp is a joy to use, delivering clean or vintage characters at will, and the 551 EQ makes the perfect partner delivering a very classy sound with well-chosen EQ options. I also liked the 543 VCA compressor a lot — it delivered exactly what I needed every time without fuss or hassle, and the versatility of the two sidechain modes is a major bonus. The new 535 diode-bridge compressor is a triumph of design that will certainly appeal to those who want characterful compression — although it’s harder-sounding and less transparent than the VCA option; I wouldn’t count it as an ‘everyday’ utility compressor. And finally, there’s the 542 Tape Emulator. This is a very clever product that introduces some very interesting and useful tonal shaping effects — again, a very useful option to have in the rack, even if you probably won’t end up using it on every source. And mentioning the rack, the R10 isn’t flashy and it has few bells or whistles, and that’s a good thing: the focus has clearly and rightly been on very good engineering, and the implementation of a handful of very thoughtful features such as the configurable link-bus arrangement.
It won’t surprise anyone that Rupert Neve Designs’ 500-series range isn’t the cheapest option on the market. However, it is not simply a case of a brand name commanding a high price; it’s very clear to me where the money is being spent in the construction, the facilities and the sound. This is all classy stuff that is beautifully engineered, sounds fantastic, and — importantly for me — is a real joy to use. I was very sad to box up the review set and hand it to the courier!
Everyone including the factory cat seems to offer a range of 500-series modules these days, and these and the PSU/chassis required to host them are available at a wide range of prices and with all manner of facilities. But very few stand comparison with these Rupert Neve Designs’ offerings in terms of the engineering and build quality, and the sheer elegance of the finished product.
RND released the six-module R6 chassis in 2015, but last year they brought out the larger R10, a 3U rack-mounting version which can hold up to 10 modules and which is reviewed here. The R10’s integral power supply is housed in the right-hand side of the unit, and its front panel and rack ears are painted in the classic RND blue-grey colour, the rest of the bodywork being black. Construction is very sturdy: there’s a steel chassis and, rather than having drilled and tapped holes for the module fixing screws, RND’s design uses captive floating nuts which allows for more leeway in module manufacturing tolerances — a very nice engineering feature.
In both the R6 and R10 the generously over-specified switch-mode PSUs are double-screened to minimise the possibility of electromagnetic interference into adjacent audio modules, and both feature a six-LED current meter to indicate how much of the capacity is being called upon by the installed modules. The R10’s meter ranges from 400 to 2400 mA in 400mA increments (the smaller R6’s meter covers 100 to 1000 mA in 200mA steps). It’s a small but very nice detail, which provides great peace of mind. The only user control is a black power button with a green status LED. However, some useful engineering features are present inside, such as the ground-lift jumper on the backplane circuit board, for separating the audio and mains safety grounds where that’s necessary.
More jumpers are located between pairs of module slots to configure the link bus — this is normally employed to share the sidechain control signal between individual compressors so their gain reduction can be matched when processing stereo/multi-channel material. The VPR Alliance standard defines a single link bus that can be accessed by all modules in the rack, but this inhibits the use of more than one pair of compressors in the same rack. The R10 and R6 neatly overcome this by breaking the bus between each pair of adjacent modules; should multiple modules need to be linked (eg. for surround projects) the link bus can be extended using the jumpers.
Moving to the R10’s rear panel, an IEC inlet accepts mains power (100 to 240 Volts AC, and drawing up to 120W), and the input and output connections are provided on both XLR and TRS sockets, wired in parallel. Thus, standard TRS patch-cords can be used to route signals between installed modules, while the main input and output connections to other studio equipment is made via XLRs — another elegant and very useful feature.
The R6 shares the same duplicated connectivity and includes a pair of AES59 (Tascam DB25) sockets for even greater versatility. (The DB25’s eight channels are allocated to the R6’s six module I/O and two further XLR/TRS sockets fitted behind the PSU module; the R10 obviously has too many slots to make AES59 sockets viable.)
- R6 six-slot PSU/chassis £595$569
- R10 10-slot PSU/chassis £795$895
- 511 Mic Preamp £570$545
- 517 Mic Preamp/DI £795$850
- 535 Diode Bridge Compressor £925$995
- 542 Tape Emulator £785$745
- 543 VCA Compressor £925$995
- 551 Inductor EQ £815$850
Prices are per unit and include VAT.
In the course of reviewing these products, as well as actually using and listening to them with a range of material, I took the opportunity to capture some measurements using an Audio Precision analyser. You can find the resulting plots, complete with captions, within this article.