Antelope Audio Zen Tour Synergy Core

Antelope Audio have turbo‑charged the desktop interface with their Synergy Core processing engine.

These days, more people than ever are recording music on Macs and PCs, and there’s a forest of audio interfaces out there. Whether you’re a laptop musician who just needs a headphone output, or a studio manager who wants to deploy hundreds of mics on a symphony orchestra, you’re spoiled for choice.

One format that has proved especially popular in recent years is the desktop interface. These typically combine hands‑on monitor control with a handful of inputs and outputs, in a stylish box that sits nicely under the hand rather than in the rack. So successful have they become that they have now begat what might be called the ‘super desktop’ interface — of which Antelope’s Zen Tour Synergy Core is a prime example.

The ZTSC, as I’ll call it from now on, is more expensive than most desktop interfaces, but the outlay brings you a much more extensive collection of I/O and features. Four built‑in mic preamps support Antelope’s Edge mic‑modelling technology, and there are no fewer than four dedicated high‑impedance sockets for connecting electric guitars, with further expansion possible through ADAT optical and coaxial S/PDIF I/O. Stereo line‑level jack outputs are augmented by a DB25 connector carrying eight more balanced outputs — DC‑coupled to permit use with modular synths — plus two independent headphone outs and two quarter‑inch sockets designed for reamping directly recorded guitars. Hands‑on control is granted not only by a large rotary encoder and three buttons, but also by a colour touchscreen, and there’s built‑in talkback.

The ZTSC supersedes Antelope’s original Zen Tour, and actually has a slightly less generous I/O configuration than its predecessor. With only a single optical input and output, the ZTSC is limited to a maximum of eight channels of ADAT expansion; a bigger loss, however, is the Zen Tour’s second pair of quarter‑inch monitor outputs, with their associated speaker‑switching functionality. Apparently, Antelope’s market research showed that Zen Tour users didn’t make much use of the additional I/O.

Where the ZTSC does improve significantly over the Zen Tour is in its audio‑processing capabilities. A major selling point for all Antelope’s audio interfaces has always been the incorporation of a field‑programmable gate array (FPGA), which can run not only an internal mixer and patchbay, but also Antelope’s low‑latency AFX effects and processors. The Synergy Core at the heart of the ZTSC is the latest and most powerful iteration of this technology, and combines two FPGAs with four DSP chips to provide a seriously capable internal audio engine.

Light Launch

The ZTSC is a neat and surprisingly compact device, about the size of a large paperback but considerably heavier. It requires a dedicated external PSU, which is attached using a locking connector. Like all of Antelope’s interfaces, it can connect to the host computer either using Thunderbolt 3 or USB. Only one cable is supplied, and there are no prizes for guessing which one it isn’t. This is a little disappointing, because anyone with the choice will surely want to hook the ZTSC up over Thunderbolt; not only do you get much better low‑latency performance, but you can pass up to 32 channels of audio between computer and interface in both directions. In USB mode, the ZTSC is restricted by the bandwidth of USB 2 to 24 channels each way.

Getting started with the ZTSC requires a live Internet connection, and as has long been the case with Antelope interfaces, you can’t open the control panel directly. Instead, you need to do so from an application called Antelope Launcher, which also handles firmware updates and detects any connected interfaces. The launching process sometimes opened two instances of the control panel simultaneously on my machine, which was odd, if not in itself a problem.

Route Marching

The basic arrangement of the Zen Tour Control Panel utility is familiar from other Antelope interfaces. A horizontal strip at the top can be switched to show input settings for the preamps, the digital inputs or the outputs, or to show various housekeeping options. There’s also a cogwheel icon which opens a Settings window, containing several quite important controls.

The colourful patchbay in Zen Tour Synergy Core's Control Panel lets you manage the many input and output connection points.

The main area of the screen is likewise switchable, and defaults to the Routing or patchbay display. This represents every possible input source and output destination within the ZTSC’s internal audio engine as a numbered, coloured block. To make a connection, you click on one or more blocks in the Input section and drag them onto blocks in the Output section. So, for example, you might want to route Preamp 5 to AFX In 5 in order to process your mic using EQ and compression, then route AFX Out 5 to Comp Rec 5, whereupon it’ll show up as hardware input 5 in your DAW. Simultaneously, you could route AFX Out 5 to an input on one of the four built‑in mixers, and have the output from that mixer dished up to your headphones for low‑latency monitoring.

This does present a bit of a learning curve, but with so many potential routing options on offer, it’s not obvious how it could be further simplified, and it’s well supported by explanatory YouTube videos and the like. Time spent getting used to it is certainly rewarded by possibilities that just don’t exist on some interfaces. For instance, with a few clicks you can set things up so that a DI’d guitar is recorded to three separate DAW tracks: once dry, once through an AFX amp simulator, and live via the reamp outputs to a real amplifier. (Hence the value of having more I/O paths to your DAW available than the ZTSC has physical I/O.) The new option to select your own colours for each input type might help anyone whose colour vision is less than perfect, and there’s also a pop‑up Matrix view for those who prefer to visualise patching on a grid.

Switching away from Routing allows you to view either one of the four mixers, with its associated Auraverb reverb, or a dedicated metering page. This presents a pop‑up selector allowing you to choose which bank of inputs or outputs you want to meter. It would be nice to have the option to display more than one bank of inputs so that you could view, say, Preamps 1‑8 and ADAT 1‑8 simultaneously. This doesn’t seem to be possible, though you can view Comp Rec 1‑32, which might come to the same thing depending on your routing.

Finally, a button labelled AFX opens a separate floating window in which you can configure the built‑in processors. This can be resized, but only ever shows two AFX slots per channel, which seems an unnecessary limitation.

Core Strength

Each generation of Antelope hardware shares a common internal platform; consequently, the Synergy Core also powers the current Galaxy 64, Orion Studio and Discrete interfaces. Individual features of the platform are activated to match the I/O on a given interface so, for instance, mic modelling is an option only on interfaces with preamps. The control panel software for each interface is likewise adapted to reflect the specific feature set on offer.

This customisation process only goes so far, and there are a few inconsistencies in Zen Tour Control Panel. For example, although Preamps 1‑4 are dedicated high‑impedance jack sockets, the panel gives you the option to select Mic or Line modes for them; and when you clock the ZTSC to an ADAT input, the Lock indication on the touchscreen lights up, but the External Sync indicator in Zentour Control remains unlit.

However, these are quirks rather than serious faults, and the good news is that Antelope have fixed the bigger issues that affected their drivers and control‑panel utilities in the past. The Thunderbolt and USB connections no longer present separate patch points in the Routing panel; the mixer faders now default to 0dB instead of ‑30dB; and the mixer pan law now makes sense. More importantly, there’s now protection to stop you deleting all your AFX settings or recalling a Zen Tour Control Panel preset through an accidental button‑press, and there’s a proper PDF manual which actually tells you the information you need to know. Most importantly of all, I found the ZTSC and the control panel stable on my Mac Mini, with no dropouts, clicks, splats or losses of communication.

It has all the power and I/O you’d expect to find in any high‑quality studio interface, and sounds just as good.

Tender Touch

Everything in the ZTSC is controlled digitally, so its touchscreen, buttons and encoder all duplicate functionality that’s available in Zen Tour Control Panel. The screen defaults to showing a bank of meters, in exactly the same way as the software Meters page Panel, and with the same options. Alternatively, it can display settings for a single preamp, for the monitor outputs, or for one of the two headphone outputs. The Gain and HP buttons respectively cycle through the preamps and the two headphone outputs, with the main encoder adjusting gain or level as appropriate. This also has a push action which mutes the selected input or output.

The third button bears an Antelope logo and can be assigned either to talkback, to collapse the main outputs to mono, or to dim the main outputs on a latching or momentary basis. The talkback signal can be routed to any or all of the two headphone outs and the monitor out, but it’s not digitised so can’t be slated; nor can it be sent to the other line outputs, which might have been a useful option. There doesn’t seem to be the option to have the main outputs automatically dim when talkback is engaged, either.

The touchscreen is a nice idea in theory, but in practice, I didn’t find it at all useful as a means of controlling the ZTSC. Its compactness means that you need absolute concentration to land your fingertips in the right place, and it’s simply easier to do everything from the mouse and keyboard. Moreover, I can’t help feeling that what screen space there is could have been better used. Given that the ZTSC has physical buttons for preamp and headphone level, why duplicate them on screen? And why allow preamp gain to be changed from the screen, but not the input type, polarity or phantom power settings? In my opinion, a better use for the touchscreen would be to display settings related to the internal mixers and AFX; I’d love to be able to adjust cue mixes or see the AFX guitar tuner. Arguably, the raison d’être of the desktop interface is ease of use, so it’s unfortunate that the ZTSC’s touchscreen doesn’t contribute more in this respect; but, thankfully, its use is entirely optional.

Tour Buses

Low‑latency performance when the ZTSC is connected over Thunderbolt is highly impressive. I had no problem operating it at a 32‑sample buffer size on my Mac, yielding a round‑trip latency of only 2.3ms at 44.1kHz. By contrast, however, the same buffer size and sample rate resulted in almost 8ms of round‑trip latency over USB. I did not have the opportunity to test the ZTSC on a Windows machine, but given that it seems to use the generic Thesycon USB driver, I’d expect to see a similar disparity there. As I’ve already mentioned, the ZTSC’s internal patchbay also presents only 24 Comp Rec and Comp Play sources when connected via USB, rather than the 32 of each available using Thunderbolt, and AFX2DAW operation is unsupported on USB. In my view it’s best to think of the ZTSC as a very well‑performing Thunderbolt interface, with USB operation a useful backup option.

Antelope have a reputation for making very good‑sounding equipment, and the specifications listed in the ZTSC’s manual are outstandingly good, though it’s not entirely clear whether some of them refer to the unit itself, or just to the converter chips. More importantly, the subjective sound quality of the ZTSC is excellent, from the clean and clear monitor outputs to the crisp‑sounding high‑impedance inputs.

Above all, the Zen Tour Synergy Core amply demonstrates the value of the ‘super desktop’ format. It has all the power and I/O you’d expect to find in any high‑quality studio interface, and sounds just as good, but sits neatly on any convenient surface. You never find yourself having to reach around the back of a rack to plug things in, and hands‑on monitor control is available exactly where your hands are! It has all the expandability you need to track a drum kit or even a full band, whilst being much more portable than any 19‑inch interface. And although the touchscreen is underwhelming, and I missed the original Zen Tour’s second pair of monitor outputs, the new unit’s massively powerful audio engine more than makes up. Most of all, though, it’s great to see that Antelope’s documentation and control‑panel software are now starting to match their always‑excellent hardware. The ‘super desktop’ interface is here to stay!

DSP, FPGAs & AFX

Antelope Audio’s interfaces have long had built‑in resources for hosting audio effects and processors. That capability takes a big step up with the new Synergy Core engine, which combines four DSP chips and two FPGAs. As well as implementing Antelope’s Edge mic‑modelling system, which requires one of their own microphones, these can host a huge range of compressors, EQs, mic preamp emulations, amp and cab simulators, a tape emulator, and various utility processors including a very welcome tuner. Different Antelope interfaces ship with a different selection of these as standard, with other compatible processors available as cost options.

Mac Thunderbolt users can use AFX processors at mixdown within their DAWs, courtesy of the AFX2DAW plug‑in — a cost option from Antelope’s online store.

The list of free AFX that comes with the Zen Tour Synergy Core is pretty substantial and includes three Pultec EQ emulations, recreations of the Gates Sta‑Level, UA 1176 and dbx 160VU compressors, and several modelled guitar amps and mic preamps. Almost 50 further AFX are available to buy from Antelope’s website, with prices ranging from €55 to €249 (for the AFX version of Antares’ Auto‑Tune). Mac Thunderbolt users can also purchase the AFX2DAW plug‑in, which allows chains of AFX to be accessed from within your DAW’s mixer in much the same way that UAD or AAX DSP plug‑ins can. This massively enhances the usability of the AFX at mixdown, ensuring you get your money’s worth from any that you’ve purchased. I tested this in Pro Tools and it worked well, with the odd limitation that there’s no mono‑to‑stereo version.

There’s no space to go into detail here, but the quality of the AFX is generally high. I particularly liked the vintage EQ and preamp emulations, which include a number of devices I’ve never seen modelled anywhere else — Blonder Tongue Audio Baton, anyone? The guitar amps too are very usable and cover most ground from classic rock and country through to modern metal, though I found a lot of them to be on the dark side sonically. I was less keen on the Reel To Reel tape emulation, which is more of a special effect than a subtle mix enhancer, and while many of the compressors sound good, their calibration is inconsistent: drop a Comp‑4k‑Bus onto your master bus and you’ll see 20dB or so gain reduction, whereas the default settings in the Gyratec X compressor will do nothing on the same material. Antelope are aware of this issue, though, and it may be fixed by the time you 
read this review.

AFX resources are, of course, finite, but not quite in the same way that those of a UAD or HDX cards are. There’s no global resource meter, because the limits apply to the number of instances of each processor, rather than to DSP as a whole. In practice, I never ran out of processing power, and with the AFX2DQAW plug‑in, I’d be happy to mix almost anything using AFX alone. I say ‘almost’ because, apart from the global Auraverb, there are no AFX delay or reverb plug‑ins. Even the guitar amp emulations don’t include reverb. I assume there are technical reasons to do with the way AFX work, but it seems a surprising omission.