FOCUSRITE REDNET ETHERNET AUDIO INTERFACE SYSTEM
Next time your corporate mates suggest your studio business might benefit from some time spent networking you’ll be able to tell them you’ve got it covered. Thanks RedNet!
Review: Andrew Bencina
Focusrite’s RedNet product line is the first ethernet audio interface system based on the Dante protocol to make a significant play for the recording studio market. Dante is an IP and ethernet-based digital AV network technology designed to eliminate the bulky point to point wiring requirements of analogue systems. The product of Australian company Audinate, Dante has become a popular standard in live sound and AV installations and the protocol is licensed by over 60 companies for use within digital mixers, stage boxes, loudspeaker processors, wireless microphone systems, amplifiers and matrix systems. RedNet relies on Dante, incorporating their hardware within each interface, so you’re not just buying into audio over ethernet but rather a specific protocol for achieving this end.
Dante imposes no limit on the total number of channels that can be present within a system — this will be restricted by the capacity and stability of the network. Any one Dante device, or link, is limited to 128 I/O at 192k (256 at 96k, 512 at 48k) over a gigabit connection. Over fast ethernet (100Mbps) the available channel count per link is reduced by over 90% (12/24/48). RedNet however doesn’t seek to push these limits and even the low-latency PCIe card has only a maximum 64 I/O channels at 192k. Multiple interconnected gigabit devices can stably achieve latencies of well under one millisecond if all devices and the network are configured correctly.
Not surprisingly, if you want to get the most from any ethernet audio system you’ll need to ensure that your network is in order. While not particularly demanding, the network spec required for the stable use of RedNet devices is a step above general home and office use. Minimum requirements include a managed gigabit switch and the use of Cat5e or Cat6 (preferred) cabling. To quote the Focusrite FAQ, “Dante makes use of standard Voice over IP (VoIP) protocols and utilises Quality of Service (QoS) switch features, to prioritise clock sync and audio traffic over other network traffic.” Don’t worry if this is all a little over your head — I myself am a network dwarf — just check the network specifications for RedNet before you buy. In my experience, any gigabit switch classified as smart (read ‘affordable managed solution’) or managed will do the trick.
To be safe, I stuck with one of the models specifically approved on the Focusrite website, picking up a ‘smart’ eight port Cisco SG-200 for about $140 new. With my desktop taking up two ports (one for RedNet control and the other for low-latency audio) I’m left with room for six other RedNet/Dante devices or gigabit links. A modular installation may choose to install a switch in every rack/room and then interconnect them at another central switch or in series. With each individual cable having a maximum limit of 100m, the breadth of any network will be game-changing for many in music production. I did read one warning against the use of switches relying on external plug pack power supplies (the SG-200 is one of these) as they may be responsible for audio artefacts or clicks. I did not have these problems but that’s not to say it won’t be an issue.
Setting up your network for Dante is easy — with a few provisos. The beauty of the protocol is that it can happily operate over the same network on which your file transfers and internet traffic are humming. In practice you’ll need to make sure you get your switch and other network hardware (routers, firewall etc) correctly configured in order to avoid incorrect prioritisation of data streams. Setting up the Cisco switch was simple enough; with a few configuration notes gleaned from the RedNet FAQ. In the case of my home studio it was then just a case of connecting everything into the switch and voila! I also tried to replicate a quick daily setup in a friend’s facility and the process wasn’t quite so stress free. In this case however, removing the modem/wireless router from the network conversation settled things immediately so we could get on with work until we had time to tweak the configuration. Focusrite does recommend that, where possible, you use a dedicated audio network and this will certainly make life easier. Dante is not compatible with wireless networks but I did manage to transmit a steady stereo audio stream over a particularly shonky ethernet over power setup. Latencies were blown all the way out to maintain audio stability at sample rates above 44.1k but for non-critical remote monitoring requirements (a green room or lounge) it was a pleasant surprise.
RedNet makes use of Apple’s Bonjour ‘zero-configuration’ service for automatic device discovery and identification. If you’re on Windows, iTunes will have generously installed Bonjour for you. I have noted online discussion of some conflicts between Bonjour and Windows 8 systems so this may be something you’ll need to resolve before moving forward. Following network configuration all that remains is to install the Dante controller and RedNet Control software on any computer that will be managing the system, and Dante’s virtual soundcard (DVS) on any computer that will be transmitting/receiving audio without the aid of the RedNet/Dante PCIe card. Theoretically, installing the PCIe card is just as easy. If you’re looking to achieve sub-3ms latencies you’ll definitely need it (which may be a problem for those based on a laptop or looking seriously at the new ‘slotless’ Mac Pro). Requiring at least a PCIe x4 slot, Focusrite does recommend using your first x16 slot if it’s available. On my Windows 7 system, this slot was already take by my graphics processor. Configuring other slots for high speed performance via the motherboard BIOS was straightforward but achieving stable operation less-so. It did take some card movement and reconfiguration before I achieved peak performance. When you’re not quite there you’ll know about it; with audio drop outs and driver instability an issue.
There are six devices that currently make up the RedNet family,
here’s a countdown:
Is a MADI bridge offering a single optical or coaxial MADI I/O in a 1RU rackmount chassis. It adds 16 channels of digital I/O at 192k (32 at 96k, 64 at 48k), Word Clock I/O, and sample rate conversion.
Offers similar digital connectivity (both 96k and 48k max out at 32 I/O) in the standard 2RU RedNet chassis; this time to a ProTools HD system via DigiLink.
RedNet 4 is really the key to any RedNet system. An eight-channel remote-controlled mic pre, it can go anywhere in your network, or even side of stage, to return your analogue sources to the recording hub. For most, this will be the first taste of RedNet you sample. Mic inputs are via XLR only, while line inputs are made available via d-sub (DB25) connector — unfortunately you don’t get to make your own choice between them. Two front-panel DI inputs are also selectable on the first two channels. Gain is adjustable in 1dB steps between 8-63dB. Front panel controls offer per-channel editing of 48V phantom power, gain, input source and analogue high-pass filters (-6dB at 65±3Hz, 12dB/octave). All of these controls being replicated in the RedNet Control software for remote adjustment.
Disappointingly, for such an ample front panel, metering on both the hardware and software interface is limited to a single multi-colour LED/indicator per channel. Also, all buttons are a little clicky, so even if you’re in the room with performers you may choose to edit things from software. At present, RedNet Control provides no option for external MIDI control so you will be stuck using the mouse. They have however, employed digital-controlled gain change using zero-crossings to make any adjustments sound as smooth as possible. You’ll notice I haven’t made mention of any outputs; because there aren’t any — not even a headphone send! While frustrating, I suspect this is entirely due to Dante’s restriction on intra-device patching (even if they were available you couldn’t configure the box with direct outputs). This places RedNet uptown in the studio interface market as most tasks will require multiple components.
They do sound pretty damn good though. Using transformer-isolated microphone splits I compared the RedNet 4’s preamps and DI inputs to those of a Universal Audio 2108, Phoenix DRS-1 and a channel of Quad Eight MM-312. On a range of sources (Fender Precision Bass DI, classical guitar, electric guitar and baritone male voice) the RedNet was always in the running. Unlike many interface preamps, it had a relaxed sound, avoiding hype in the upper mid range and any fizzy air. In contrast, the bottom end was solid. When it came to select tracks for a quick mix, the RedNet got the nod for the nylon string guitar. While never sounding cloaked, the finger-picked performance was captured truthfully without instant demand for EQ to attenuate the stringy-ness that can often prevail. If I had to use only the RedNet, I would feel like I was trading off some depth and dimension offered through the combination but I wouldn’t be let down.
RedNet 3 is a 32 I/O digital audio interface featuring eight ADAT I/O (ports 5-8 mirror 1-4 at sample rates 48k and below, becoming active for SMUX operation at 96k and 192k), eight-channel AES/EBU via DB25 connector, two-channel coaxial SPDIF and word clock I/O. I experimented with the RedNet 3 in between my existing RME PCIe interface and ADAT converters as a means of integrating audio over ethernet into my current system. While this was largely successful, again the intra-device patch limitations of Dante do restrict some interesting possibilities. While recording tests under full RedNet operation showed solid syncing of my external converters over ADAT, there was a sample offset between the RedNet and RME channels (as you’d expect) so this is worth keeping in mind if you intend to mix and match.
The RedNet 1 (eight I/O) and 2 (16 I/O) are the workhorse ADC/DAC components of the RedNet system. Delivering Focusrite’s most advanced 24-bit/192k audio conversion to date. It’s difficult for me to go into too much detail in this overview but further information is available here (global.focusrite.com/the-sound-of-rednet) for those interested. Analogue line I/O is again catered for by eight-channel DB25 connectors. Particularly in the case of the RedNet 1, this seems a little short-sighted, as the 2RU chassis would seem to provide ample panel real estate for some XLR, TRS or combo connectors. In an install situation when boxes may be shifted around on a regular basis there is certainly an advantage to the inclusion of dsubs, but the omission of more commonly used connectors will probably cause frustration for some. Two global calibration levels are switchable via software (+18dBu or +24dBu) but there were times where I would have loved independent control over the calibration for A-D and D-A and indeed some form of fine level trimming to match other devices or analogue meter calibrations. Again, like RedNet 4, the metering is limited; but this is unlikely to bother you if all of your converters live in a machine room. I thought all of the converters used in the RedNet components sounded classy. In blind ABX testing with a few different converters of comparable expense they performed well without standing out. Indeed, a commitment to transparency rather than any particular aesthetic of analogue enhancement was a key tenet of RedNet’s design philosophy and on this front they’ve succeeded.
REDNET IS GO
Configuring your RedNet system for use in your DAW, or as a standalone signal transfer system, is as simple as colouring in squares on the Dante Controller’s matrix to connect Dante transceivers and receivers. There is no signal monitoring incorporated so at times tracking down that input can get a little confusing (especially when ADAT SMUX is involved!). Using the PCIe card, I found that only channels patched in the controller appeared as available I/O in my DAW. The Dante Virtual Soundcard driver can be easily enabled or disabled when required and in its ASIO mode I found it to be really solid. My own studio machine has gigabit ethernet on-board, and I was able to achieve stable multichannel performance and relatively low latencies even without resorting to the PCIe card. Channel count is limited however and while, to me, the latency felt far tighter than the supposed 4ms limit it’s possibly not a viable permanent solution where live monitoring is critical.
With my PCIe configuration sorted, I was able to record 24 channels of 96k audio with stable monitoring at well below 1ms latency. Sample rate, buffer settings and clock assignments are all located in the RedNet Control panel and you’ll probably want to keep this open most of the time. Running RedNet under ASIO, it wasn’t possible to just jump around between programs using different sample rates willy nilly as I normally do and occasionally this caused short term confusion. I found the lack of Dante matrix metering, intra-device patching and any software mixer meant that ultimately my preferred method was to continue using my everyday interface and driver with RedNet integrated via RedNet 3’s digital interface. If you’re a ProTools HD user or already have a MADI interface this is what I’d currently recommend. In a perfect world, I’d love to see a new Focusrite Saffire Pro Thunderbolt/USB 3 interface that included a Dante link. Alternately a new custom RedNet Thunderbolt/USB 3 interface (RedNet 7? aka ‘Brains’) with expanded driver functionality, word clock I/O, MIDI, eight channel ADC/DAC, two mic pre/DIs, headphone output and critically dual Dante links for sends and returns. With two of these you’d be ready to rock and roll tape anywhere.
I SEE RED
For those committed to the Dante digital media networking platform Focusrite’s RedNet range is an obvious choice to augment your work flow. From painless live recording to concert mixing in the box; RedNet and Dante expand the options for mobile musicians. Check out the case studies (global.focusrite.com/rednet-case-studies) for more ideas. For everyone else, RedNet opens up new possibilities for the flexible use of existing networked spaces and a more efficient way to access currently installed resources. If you’re based in-the-box, your existing audio interface’s software may still offer greater flexibility and functionality but with RedNet components designed for direct integration with ProTools HD, MADI, ADAT and AES/EBU systems there’s no reason why you can’t have it both ways. If you’re going to tape, RedNet can be used to connect any room with an ethernet link to your main studio, allowing the use of your primary recording hardware for capture of sources in distant performance and rehearsal spaces. For institutions looking to break ground on or upgrade a large installation, the connection of performance, recording and broadcast facilities through existing network infrastructure may be temptation enough. For smaller studios the current requirement for additional units to create a flexible set-up may make RedNet a little less attractive/affordable. Either way, you’ll need to be particularly fond of the colour red.