You are here

Rupert Neve Designs RMP-D8

Eight-channel Dante Mic Preamp By Hugh Robjohns
Published September 2020

Rupert Neve Designs RMP-D8

This remote-controllable preamp boasts some unusual features aimed largely at the live-sound market.

Audio-over-IP (AoIP) continues to gain popularity, particularly in live-sound and broadcast applications, and Rupert Neve Designs have recently joined the network-audio crowd, with the release of the RMP-D8. This eight-channel, remote-controllable microphone preamp incorporates the almost ubiquitous Dante AoIP interface, and although aimed primarily at live-sound applications, it offers exemplary audio quality and simplicity of use for any Dante-equipped installation, so should also find welcoming homes in the broadcast, education, studio-complex and location-recording sectors.

Controls & Construction

The RMP-D8 looks nothing like any other RND product I've seen. With its sturdy 2U rackmounting steel chassis and control panel, both finished in plain matt black, it's far more industrial-looking than the Portico or Shelford ranges. Ten vertical slots milled into the substantial front panel reveal eight digital bar-graph meters and two LED arrays of status indicators. User controls comprise 15 illuminated buttons for channel access and configuration, a big red indented rotary encoder, a black power button, and a small colour OLED display.

All the usual preamp facilities are provided for each channel, with individually switchable 48V phantom power, polarity inversion, a 10dB pad, an 80Hz (12dB/octave) high-pass filter, and gain that's adjustable between 0 and +60 dB in 1dB increments. If the line input is selected, the gain range is restricted to a maximum of +30dB, phantom power is automatically disabled, and the pad is engaged. A Reset button restores all channels to their default settings.

When one of the channel buttons under the meters is pressed, that channel's settings are shown on the OLED screen. The preamp's gain is displayed in large numbers, along with the status of the phantom power, high-pass filter, pad and polarity options. Also shown is whether gain compensation (GC) is active (more on that later), and whether the front-panel controls have been locked. Additional menu screens show system information like the current firmware version, PSU voltages and temperature, the Dante connection IP/Mac addresses, Dante software and ID details, and the device ID for use with remote control from Yamaha CL, QL or PM consoles.

The preamp functionality is obvious and efficient, making routine setups and operations straightforward, but the 20-page manual is necessary reading if you're to understand the more involved Dante configuration functionality. The only thing I felt was missing was an instant overview of all channel settings; the assignable nature of the controls means that the unit's front panel can't provide that overview, so I'd very much like to see an overview display page added to the OLED screen in a firmware update.

The RMP-D8 has a dual redundant power supply, with separate IEC inlets for each.The RMP-D8 has a dual redundant power supply, with separate IEC inlets for each.The RMP-D8 features true mains power redundancy: there are two separate universal voltage (100-240 V AC) power modules, each fed from separate mains supplies, with their outputs switched automatically if one supply (or PSU) fails. The two provided mains cords are fitted with locking IEC plugs, too, so there's zero risk of the cables falling out after being bounced around in a wheeled rack or an OB truck. These provisions are important for applications where the equipment serves in 'mission critical' or arduous roles. There's a cooling fan, but it's temperature-controlled and quiet: on the occasions it decided to run I could barely hear it, even when right beside me on the desk.

The eight mic/line inputs are connected via a single row of combi XLR/jack sockets on the back panel, and phantom power is never present on the TRS connections. I was surprised at the omission of a multichannel input connector; there's plenty of space for a couple of AES59 D‑sub connectors for separate mic and line inputs, for example. Another surprise was that there are no analogue outputs: no line-level preamp outputs, and no headphone socket for local monitoring, which would have been useful for checking connections and settings during rigging, or when fault-finding. There are four male XLRs carrying AES3 digital outputs from all eight channels, although I'm struggling to imagine what these would typically be used for. Also on the rear panel is a USB‑A socket for firmware updates, and a pair of RJ45 sockets providing primary and secondary Dante network connections.

Surprisingly, there are no analogue outputs: no line-level preamp outputs, and no headphone socket for local monitoring, which would have been useful for checking connections and settings during rigging, or when fault-finding.Surprisingly, there are no analogue outputs: no line-level preamp outputs, and no headphone socket for local monitoring, which would have been useful for checking connections and settings during rigging, or when fault-finding.

Signal Path

As you'd expect of a Rupert Neve Designs product, the analogue circuitry is described as Class‑A and each channel features a custom-designed transformer. These are not the mic input transformers you might have expected, though; the front end is actually electronically balanced with an 'instrumentation amplifier' circuit topology. Instead, the transformers reside in the channel output stages feeding the A‑D converters, and are credited for delivering the 'larger than life' tone so often associated with Rupert Neve's preamps.

Apparently a lot of attention has been paid to the RMP-D8's digital clocking and jitter-reduction arrangements, and its 24-bit converters support all the standard sample rates between 44.1 and 192 kHz. Unusually, the four common pull-up/pull-down sample-rate modifiers required for some film/TV shoots are also provided (±0.1, -4 and +4.1667 percent). As a pure Dante interface, the desired sample frequency can only be adjusted via the Dante Controller application; there's no provision to adjust the sample rate locally.

Dante & GC Outputs

Although an eight-channel preamp, the RMP-D8 actually presents 16 outputs to the Dante network. The main outputs are labelled channels 1 to 8, as you'd expect, while channels 9-16 can either be straight duplicates (mirrors) of the first eight channels, or 'gain compensated' (GC) versions, selectable on individual channels.

This 'GC' refers to a feature whereby the channel gain can be adjusted for the output without affecting the previously set gain structure. For example, if Channel 1's gain is turned up, the GC output has its gain turned down automatically to compensate, thus maintaining a consistent level at that output. The GC outputs always start with 6dB less gain than the main outputs, to build in some working headroom, and the automatic gain compensation only works over a ±12dB range, and within the limits of the preamp's 0-60 dB overall gain range.

Why is this facility provided? Well, in a typical live-sound setting the main (1-8) outputs would typically be routed to the FOH console and the GC (9-16) outputs to a stage monitor console. During the soundcheck, let's say channel 1's gain of +36dB is stored as the initial setting, and the gain to the GC output will therefore be +30dB. During the show, the FOH engineer wants a bit more level and tweaks the gain up to +40dB, the GC output to the monitor desk will still have 30dB of overall gain, so the artists' monitoring feeds don't change either.

While the FOH engineer could use the front-panel encoder to change channel gains, the RMP-D8 can also be controlled remotely over the Dante network; RND provide free Mac/Windows remote-control applications that run alongside the Dante Controller and it's possible to control the preamp channels directly from any Yamaha CL, QL or PM digital console (the RMP-D8 appears as a native Yamaha RIO preamp, allowing control of gain, phantom power and high-pass filter settings).

RND's remote control app provides a graphical representation of the eight channels, with gains being adjusted either via on-screen knobs or by typing in numerical values, and switch functions are toggled by clicking the on-screen buttons. Setting up this interface is a bit 'geeky', but it works well. Although the app version I used during the review could only control one physical RMP-D8, RND were already beta-testing an updated version which can address eight units simultaneously, and that should be available by the time you read this.

Performance

As you might expect, the RMP-D8 boasts some very solid technical specifications, all of which I confirmed with an Audio Precision test system. The mic preamp EIN figure (150Ω source, 60dB gain, 20Hz-22kHz bandwidth) measured the equivalent of -127dBu (-92.5dBFS at the AES3 output), and the system noise floor at unity gain was -100dBFS. The AES17 dynamic range figure measured a tad over 115dB (A-wtd), putting it on a par with the Audient ASP880 and Antelope Orion. The THD figure was 0.007 percent with an output level of -0.5dBFS, showing a slight emphasis of odd harmonics over the even ones, thanks presumably to the output transformer.

The frequency response is easily within ±0.25dB from about 30Hz up to just below the Nyquist frequency, and I measured the low-frequency -3dB turnover point at 10Hz, rising to 80Hz with the second-order high-pass filter engaged. The input impedance is a Neve-classic 5.3kΩ for both mic and line modes and, unusually, it doesn't change if the input pad is activated. The unloaded phantom power voltage was fractionally low, but comfortably within spec at 46.9V, and it delivered 10.8V at the microphone when providing the maximum 10mA current, which is also safely within spec.

The maximum input level corresponding to 0dBFS (digital clipping) is +25.5dBu, while the SMPTE specification calls for +24dBu, so RND have effectively built 1.5dB of extra headroom into the conversion. (While this is potentially useful in a live-sound situation, it means a standard +4dBu analogue reference doesn't generate the expected -20dBFS digital output. Thankfully, only engineering geeks like me would fret about such trivial anomalies!)

As you might expect, the RMP-D8 boasts some very solid technical specifications, all of which I confirmed.

In Use

Once the RMP-D8 is integrated into a Dante network, it's very easy to use both from the front panel and remotely. The bar-graph meters show -60 to -9 dBFS across five green LEDs, with two oranges for -6dBFS and -3dBFS followed by a (helpfully pessimistic) red overload LED. (I like a little more warning of high peaks, and would have preferred the -9dBFS LED to be orange.) Unfortunately, setting high gains from the front panel can be rather tedious, because the encoder isn't speed-sensitive — a lot of revolutions are needed to reach +60dB. The controller app is a lot faster in that respect. I also couldn't find a way to pair channels for convenient stereo operation.

Although the RMP-D8 is intended to be used with a Dante network connection, it can be used as a standalone preamp/converter under certain circumstances. The unit retains in memory its Dante-programmed clocking configuration and restores that setting when the power is cycled. So if the unit is connected to a computer running the Dante Controller and programmed to use its internal clock, it retains that capability afterwards, allowing use as a free-standing preamp with AES3 outputs. It's not particularly convenient, but it works!

Sound-wise the RMP-D8 is great, being quiet and generally clean, with more than enough gain for most live-sound applications. The standard facilities are effective and working with normal headroom margins delivers a sound which is full-bodied and does have a slightly larger-than-life character associated with well-engineered mic preamps. It's not obviously coloured, but intentionally driving signals into the red results (initially) in a progressively saturated distortion rather than the more typical hard aliased clipping.

Although I feel there are a few areas where some minor firmware updates would be beneficial, overall this is a good Dante preamp and should do well in the AoIP live-sound market for which its unusual feature set has clearly been focused.

Alternatives

There are now several octal Dante mic preamps, and some of them share a Rupert Neve heritage. These include Neve's new 1073OPX and Focusrite's older ISA828 MkII (which can be equipped with a Dante interface, but it isn't remote-controllable). Focusrite's Rednet MPR8 is remote-controllable, though, and also has dual-redundant power supplies. Other remote-controllable eight-channel Dante preamps include Glensound's DARK8MAI, Grace Design's m802 and Millennia's HV‑3R.

Technology

The dual power modules can be seen at the bottom of the image just behind the front panel, with the fan to the right. Four dual-preamp boards are mounted on stilts above the motherboard, their line output transformers aligned across the middle of the unit. All the control electronics, micro-controller and most of the digital audio interfacing are on the right half of the motherboard, with the A‑D converters being hidden under the preamp modules. The red plug‑in Audinate Brooklyn II card provides the Dante formatting and management facilities.The dual power modules can be seen at the bottom of the image just behind the front panel, with the fan to the right. Four dual-preamp boards are mounted on stilts above the motherboard, their line output transformers aligned across the middle of the unit. All the control electronics, micro-controller and most of the digital audio interfacing are on the right half of the motherboard, with the A‑D converters being hidden under the preamp modules. The red plug‑in Audinate Brooklyn II card provides the Dante formatting and management facilities.

The RMP-D8 is built to a high standard, and it all looks very rugged and reliable. The two switch-mode power modules are located just behind the front panel, with cooling when required from a quiet temperature-controlled fan on the right-hand side.

All digital audio and control electronics are accommodated on a large motherboard, with four dual-channel preamp modules mounted above. Proper RF filtering is provided at the XLR inputs and the circuitry for each preamp channel comprises half a dozen op-amps (mostly NE5532s), along with nearly 20 discrete transistors. Digital gain control appears to be courtesy of a THAT 5173 chip, although that increments in 3dB steps, not 1dB, so there's something clever going on somewhere!

Custom line transformers convey the preamp outputs to AKM AK5388 four-channel A‑D converters located on the motherboard, and each one handles the signals from the pair of preamp boards mounted directly above. This particular AKM converter features a modified linear-phase FIR filter architecture which minimises the group-delay, providing an analogue input to Dante output latency of under 0.6ms at a 96kHz sample rate.

Digital signal processing, presumably for the gain-compensation mode but also probably providing the 1dB gain adjustments and sample-rate manipulation for the pull-up/down rates, is provided by a pair of D2-Audio D2-92633 DSP chips, while an AKM AK4101 interface provides the AES3 outputs.

Pros

  • Dual redundant mains supplies.
  • Classic larger-than-life sound character.
  • Very solid technical performance with generous headroom.
  • Remote-controllable and compatible with Yamaha's RIO system.
  • Provided with locking IEC cables.

Cons

  • No display overview of all channel settings.
  • Fixed-speed encoder makes setting high gain values tedious from the front panel.
  • No analogue outputs or local headphone monitoring.

Summary

Optimised for professional live-sound AoIP installations, the RMP-D8 provides a high-quality eight-channel, remote-controllable preamp with full Dante connectivity.

information

£5499 including VAT.

Rupert Neve Designs UK & Europe +44 (0)208 191 0058

info@rupertneve.com

rupertneve.com

$5995.

Rupert Neve Designs +1 512 847 3013.

info@rupertneve.com

rupertneve.com

Published September 2020