Universal Audio Arrow

The Arrow offers two-channel recording and UA’s celebrated plug-ins, all at the end of a Thunderbolt 3 connector.

The Universal Audio Arrow, compatible with macOS and Windows, builds on the technology already used in the Apollo range of products to combine a bus-powered audio interface with the ability to run any UAD DSP-hosted plug-ins using its onboard SHARC-based UAD2 Solo Core engine. Furthermore, it includes the Apollo’s ability to run plug-ins with Realtime UAD Processing, courtesy of its Console software, which means you can record through the plug-ins, or use them for monitoring purposes without incurring the usual latency issues encountered when using DAW-hosted plug-ins. Of course there is no such thing as zero latency, as it takes maybe the best part of a millisecond for the A-to-D and D-to-A converters to do their thing, and even the slickest coding can’t stop the various plug-ins and the control Console software adding a further tiny delay of their own. But in reality the delay when using Realtime UAD Processing is so small that for all practical purposes it can be considered as being zero latency — typically below three milliseconds at a 96kHz sample rate and maybe twice that at 44.1kHz.

Another major feature that Apollo brings to the Arrow is Unison, which really is quite a big deal and is unique to UA. Arrow’s two Unison-enabled mic preamps have the ability to reconfigure their analogue signal path according to the plug-in being used. For example, when you track via one of the Unison-enabled plug-in emulations of, say, a preamp or guitar amp, the analogue input stage of the Arrow switches its impedance and gain-staging to replicate the behaviour of the modelled device based on component-level analysis of the original hardware. When you load a Unison-enabled UAD preamp, guitar amp or console plug-in, data within the plug-in instructs the Arrow on how to configure its input stage.

Connections

The Arrow is billed as the first Thunderbolt 3 audio interface and is a two-in, four-out device. All four outputs are independently addressable via the Console Setup page so, for example, the monitor mix can be different from the loudspeaker mix. You can also set up Console to include two aux sends and also Virtual Inputs fed from DAW outputs. Both aux sends can also be used as separate feeds into the DAW, providing the ability to control the level of reverb or delay separately from the dry signal on playback.

Conversion is 24-bit at sample rates up to 192kHz. Power comes directly from the Thunderbolt bus, but be aware that you will need to provide your own Thunderbolt cable. It is also important to appreciate that not all USB-C cables work correctly as Thunderbolt 3 cables, so you’ll need to choose one that is certified for Thunderbolt 3 use — look for the lightning symbol on the connector. Cables up to half a metre in length are passive, whereas longer ones include some active components and cost a little more, though both types will work as long as they are correctly certified. More information is available on the UA web site if you are still unsure what cable to buy.

The reason the Arrow was conceived as a Thunderbolt 3 device when Thunderbolt 2 would be perfectly fast enough, was so that it could be bus powered. UA’s engineers tell me Thunderbolt 2 can’t provide sufficient power for the Arrow’s converters, preamps, 48V phantom power and DSP chips, which use up most of Thunderbolt 3’s 15 Watts of bus power capacity. In theory, the Arrow could be made to work with Thunderbolt 2‑equipped computers, but this probably isn’t practical, as an expensive powered external hub would be needed to provide power to the Arrow. However, you can combine an Arrow and a Thunderbolt 2 Satellite in the same system using appropriate adaptor cables. It is possible to cascade up to four Universal Audio interfaces or to add UAD2 Satellite devices (up to a maximum of six devices in total) over Thunderbolt to add both DSP capability and I/O.

Things are pretty simple at the back of the Arrow, with just a Thunderbolt 3 connector, stereo quarter-inch outputs and combi XLR/jack inputs.

The Arrow has two combi XLR/jack mic/line preamps, a pair of balanced monitor outputs on quarter-inch jacks to feed your monitor speakers and a stereo quarter-inch headphone output on the front-panel. Also sharing the front panel is a Hi‑Z instrument input for use with guitars and basses.

It is worth commenting on the physical aspects of Arrow as it has an ergonomic yet compact desktop profile and the casework is made from a seamless piece of metal, which I assume to be a casting. A piece of grippy rubber covers the base. An illuminated panel shows the input levels and Monitor/Phones levels on five-section bargraph displays, below which are illuminated status indicators to show input selection, input type, low-cut filter active, +48 Volt phantom power active, pad, polarity invert and link, as accessed using the six buttons below the display. There’s also a rotary LED bar display around the large knob, which operates as a continuous controller to adjust input gain or monitor level. An integrated push switch acts as a monitor mute, whereon the LED ring changes from green to red. Two further dedicated buttons select Preamp and Monitor (monitor/phones switching) for gain or level adjustment.

Console

Though you could just plug in the Arrow, install the software (VST, RTAS, AAX 64 and Audio Units plug-in formats are supported) then use your UAD plug-ins or other third-party plug-ins within your DAW in much the same way as any other audio interface, the key to accessing the real-time and Unison capabilities of the device is to use the included Console 2.0 software control interface. This follows a familiar console channel strip format and sits between the Arrow and your DAW, and allows you to track via the plug-ins or, alternatively, to track clean but to monitor via the plug-ins. Console 2.0, which is essentially the same as that used for the Apollo units, also allows remote control of the Arrow’s hardware features and provides switching options using bi-directional communication so that changes on the Arrow unit are reflected in Console and vice versa.

Console sessions can be saved for later instant recall while virtual I/O allows for the routing of DAW channels into Console or Console channels into the DAW for recording/monitoring purposes. There are Level, Pan, Solo and Mute controls on all inputs and on the two stereo auxiliary sends. Adjacent inputs can be linked as stereo pairs while the two aux returns may host up to four plug-ins each.

The Arrow Mixer within the Console 2.0 software showing Unity plug-in inserts.The Arrow also serves as a monitor controller and the Console 2.0 software provides mute, solo, dim and source select controls as well as volume and mono summing. Console’s input meters are globally switchable to display pre- or post-fader signal levels with selectable peak/clip hold along with a button to clear the clip’s display. A resources meter indicates current DSP and Memory usage and within the I/O Matrix is the ability to add custom names for Core Audio or ASIO I/O.

Within Console, each input channel provides the option to insert the plug-ins into the record path or the monitor path in a Unison plug-in area in the Input section (only Unison-enabled plug-ins show up in the Unison insert slot) and also offers up to four conventional inserts in the channel Inserts view. The Virtual inputs and outputs handle the routing between Console and the host DAW and the default setting sends the DAW’s main outputs directly to the Monitor Control section. All the console features are visible at all times and the screen size can be reduced to limit the number of channels on display, though alternative view options are also available for when you need to focus on, for example, the aux sends.

Operation

My tests were carried out using a 2017 quad-core iMac running Sierra with Logic Pro as the host DAW, and there was very little to do to get up and running with the Arrow. In order to enable the physical panel controls to adjust the input functions the Arrow needs to be in preamp mode, accessed by pressing the Preamp button — though the Console software can access the controls whether or not the hardware is set to Preamp mode. Either of the two preamps can be selected for adjustment, and the currently selected channel is indicated by the illuminated CH1 or CH2 legend above the input meters. Channel 1 can be switched, using the Input button, to Mic or Line mode and Hi‑Z mode is selected automatically by plugging into the Hi‑Z jack. Channel 2 offers a choice of Mic or Line only. When the Arrow is switched to Monitor mode, the physical panel controls allow the user to adjust the speaker and headphone levels.

While Console allows all of UAD’s plug-ins to be used in real-time mode for tracking or monitoring, plug-ins hosted within the DAW itself are subject to the same latency limitations as when using any other audio interface. To minimise latency, that means setting the lowest possible stable buffer size in your DAW, particularly when recording virtual instruments. When using UAD plug-ins within the DAW for mixing, a small additional latency will be experienced due to the need to send the signal to the Arrow and back again. Using the low-latency button in a UAD plug-in window reduces this latency to minimum at the expense of using more CPU power — a useful feature when tracking.

Logic Pro also has a separate ‘Process Buffer Range’ setting that affects the buffering of plug-ins, so you could set this to Small rather than the default setting of Medium for lower latency as long as your system remains stable on that setting. With a Medium Process Buffer setting, Logic Pro reported a round-trip latency of 12.9ms at 44.1kHz, which is similar to what I read from my other non-UA interfaces. However, I did further tests at Logic’s minimum 32 samples buffer size, with the Process Buffer set to Small, and recorded round-trip latencies of 4.2ms at 32 samples, 5.7ms at 64 and 8.6ms at 128. When monitoring via the console directly latency is steady at around 2.5ms, so the response when using real-time or Unity plug-ins feels very immediate. Normally I’d use a buffer size of 64 or 128 and a Logic Pro Process Buffer setting of Medium to ensure stability, but even with those settings the round-trip latency was no worse than around 12ms at a 128 samples buffer size running at 44.1kHz.

In most cases I don’t find latency presents a problem with a 128 buffer size, but for guitar playing, using the Unison-enabled Marshall Plexi does somehow feel more natural and tactile than using DAW insert plug-ins with a generic Hi‑Z interface input. And it sounds really good too.

Impressions

With only a single processing core, the number of UAD plug-ins that can be run at the same time is necessarily limited, and depending on which plug-ins you choose, even running two of the greedier ones together can overtax it, in which case the one already loaded is automatically disabled. In other cases you might find that you can run four or more plug-ins with no problem. To give a practical example, a vocal chain that runs at around 90 percent of the Solo DSP Core capacity at 44.1kHz, and that can take advantage of near zero-latency monitoring via the Console software comprises, in order, the Neve 1073 Preamp & EQ Unison, the Fairchild 660 Tube Limiter, the Precision De-Esser and Oxide Tape with Aux 1 sending to the EMT Plate 140 and Aux 2 to the Cooper Time Cube for slap delay.

If you need more capacity and bus powering doesn’t matter to you, then moving up to a multicore Apollo Twin MkII might be a better option. Or you could add a UAD Satellite to your system if you need more plug-ins at mixdown, assuming of course that you have a recent TB3-equipped computer with two Thunderbolt ports. A TB3 to TB2 adapter would allow the TB2 racks and satellites to daisy-chain into one port with the Arrow connected to the other. A TB3 option card is also due to be released for Apollo rack units later this year.

On its own, the Arrow is ideal for working on the move as its bus powering makes it possible to record and mix away from mains electricity — such as when enduring a train or plane journey. The Unison feature is also a great asset for those who only need to record one part at a time but want ultra-low latency monitoring, while the included plug-ins are worth the price of admission on their own.