Roundup: Thunderbolt Interfaces

Our guide to interfaces for any studio rig, from budget to top-of-the-line
By Geary Yelton ,

If you’ve purchased a Mac in the past few years, you’ve probably noticed it has a new type of connector. Every Apple computer made since 2011 sports at least one Thunderbolt port, which has recently replaced the once ubiquitous FireWire ports that graced previous generations. The reason is that Thunderbolt is much, much faster than any of its predecessors. USB connectors are still onboard because USB is so universal, but Thunderbolt transports audio and other data with speedier throughput, resulting in greatly reduced latency, more numerous DAW tracks, smoother operation, and a better experience all around.

With Apple’s participation, Intel Labs developed Thunderbolt as a high-speed interface for connecting computers to external devices. It lets you connect the PCI Express bus directly to peripherals, supplying them with DC power and providing the fastest access to your computer’s main logic board that modern technology can muster. The original Thunderbolt, now called Thunderbolt 1, has a transfer rate of 10Gbps—20 times faster than USB 2.0 and 12 times faster than FireWire 800. Thunderbolt 2 is twice as fast as the first version, and the latest Thunderbolt 3 is a blazing 40Gbps.

Thunderbolt enables daisy-chaining of as many as six devices if at least five of them have two ports and any single-port device is the last in the chain. That makes the number of ports a consideration when choosing any Thunderbolt device, including an audio interface. Cables can each be almost 10 feet long. If you own any pricey FireWire gear, don’t fret; Apple’s Thunderbolt-to-FireWire adapters work like a charm.


Typically, an audio interface is an AD/DA converter that converts analog audio signals to digital and digital signals to analog. It’s what you use to get high-quality audio into and out of your computer. Audio sources are connected to the inputs, and the outputs are usually connected to amplified monitor speakers or mixing boards. Most audio interfaces also house two or more microphone preamps and a clock generator for synchronization, and the whole shebang is packaged in a tabletop or rackmount unit with various jacks, ports, and sockets to connect it to the outside world. Most have individual jacks for each analog input and output, and some have D-sub sockets that require an audio snake with a 25-pin plug at one end and numerous XLR or TRS jacks or plugs at the other. Most also have some sort of digital audio connectivity, usually stereo S/PDIF or ADAT Lightpipe, which carries a maximum of eight channels, depending on the sampling rate.

Many audio interfaces come bundled with software that lets you adjust parameters, route inputs to outputs, apply effects processing, and control mixes from the comfort of your computer screen. Because Thunderbolt offers such lightning-fast throughput, all of the interfaces mentioned in this roundup claim near-zero latency, and all have the numbers to back up their claims.



It can’t be easy to design and build a studio-quality Thunderbolt audio interface practically any musician could afford, but that’s exactly what relative newcomer Resident Audio has done. Holding down the budget end of the Thunderbolt spectrum, the T2 (Mac, $150) provides two channels of 24-bit, 96kHz AD/DA conversion at an unbeatable price.

The T2 is housed in a 1/3U chassis that you can rackmount, but it doesn’t come with any mounting hardware. Two combo XLR/TRS jacks on the front panel are the only audio inputs. They accept signals from microphones, line-level sources, or high-impedance instruments like guitars. A switch sets both inputs to instrument or line-level impedances, and another enables phantom power for both inputs. Two knobs for controlling input gain are encircled by wraparound LEDs that indicate signal level in three colors. A large knob determines the main output and headphone levels, and a smaller knob determines the mix between the two inputs and any audio streaming from your computer.

The back panel comprises two line outputs on TRS jacks, a 1/4-inch stereo headphone jack, MIDI In and Out on DIN connectors, and a single Thunderbolt port. During playback, you can switch the outputs from stereo to mono, which may be helpful for singers or DJs who want to hear the entire mix through one side of their headphones. Unlike most of the other interfaces in this roundup, the T2 is bus-powered, which means it has no power supply of its own but draws enough current to operate from your computer through the Thunderbolt cable.



Next up is the multichannel TAC-8 (Mac, $650) from a company best known for multi-effects pedals and handheld multitrack recorders. Only $250 more than the 2-channel TAC-2 launched in 2014 (TAC stands for Thunderbolt Audio Converter), the TAC-8 is a 1U rackmount unit with eight analog inputs, ten analog outputs, and up to ten channels of digital audio I/O—up to 18 inputs and 20 outputs in all, not including two 1/4-inch stereo headphone jacks with independent level knobs. A switch enables standalone mode, in which you can use the TAC-8 as an 8-channel mic pre and AD/DA converter without connecting it to a computer. According to the manufacturer, the TAC-8 can eliminate aliasing noise by internally upsampling 44.1 or 48kHz audio to 176.4 or 192 kHz.

Eight combo XLR/TRS inputs are on the front panel, each with its own individual gain knob and LED to indicate signal and clipping. Handy hi-Z switches on the first two inputs mean you can plug an electric guitar or bass into either of them. A large output knob controls levels for all outputs simultaneously, and two 48V switches enable phantom power for four inputs at a time. Around back, you’ll find eight individual channel outputs on TRS jacks and a separate pair for the main output, as well as 8-channel ADAT I/O on optical ports, stereo S/PDIF on coaxial jacks, word clock I/O on BNC connectors, and MIDI In and Out on 5-pin DIN connectors.

TAC-8 MixEfx is the bundled application for controlling the TAC-8 from your Mac. It provides access to parameters such as sampling rate, clock source, and so on, and it also functions as a signal router and mixer. In addition, MixEfx lets you use the included effects plug-ins—three reverb algorithms and delay—but only if upsampling is disabled.



Founded by legendary studio hardware designer Rupert Neve, Focusrite first made its mark building outboard audio processing modules beginning in 1985. Although Mr. Neve sold the company four years later, its current products carry over that heritage. For decades, Focusrite’s product lines have been distinguished by colors—Red, Blue, Green, Platinum, Saffire, and Clarett—indicating their target market and cost. The Clarett line comprises four relatively affordable Thunderbolt interfaces. As the name indicates, the Clarett 4Pre (Mac, $700) has four mic preamps and sits smack between the dual-preamp Clarett 2Pre and 8-preamp Clarett 8Pre. (The top of the line is the 8PreX, which has additional I/O functionality.)

Not to be confused with the $2,500 Red 4Pre, the Clarett 4Pre boasts 24/192 conversion with up to 18 simultaneous inputs—8 analog and 10 digital—and 8 outputs. The front panel has four combo XLR/TRS inputs that accommodate mic or line-level signals, with another four 1/4-inch line inputs on the back. An optical input furnishes either 2-channel S/PDIF or up to 8-channel ADAT, and a pair of coaxial jacks furnish stereo S/PDIF in and out. Four balanced TRS outputs are in back, and two 1/4-inch headphone outputs up front have independent level knobs. The interface also has two 48V phantom power switches (one for each pair of front-panel mic inputs), along with MIDI In and Out on DIN connectors and a single Thunderbolt port.

The Clarett 4Pre’s low-noise mic preamps are equipped with Focusrite’s exclusive Air effect. Air models the classic Focusrite ISA mic pre by duplicating the interaction between preamp input and microphone impedance, which has a substantial influence on a mic’s clarity and character. All Clarett interfaces come with Focusrite Control software for controlling the 4Pre’s internal audio mixer and parameters such as S/PDIF source and sampling rate, which affect the number of digital audio channels available.



In 1999, recording pioneer Bill Putnam’s sons resurrected their late father’s company to design and market software emulations of classic studio gear. Universal Audio still makes analog hardware, but its real bread-and-butter products are the UAD plug-ins that model studio hardware with jaw-dropping accuracy. However, you can’t use any of them unless they’re hosted on UA’s DSP accelerator hardware. The Apollo line of audio interfaces combines internal SHARC DSP processors serving as accelerator cores with superb mic preamps, pristine AD/DA converters, and analog and digital I/O.

The priciest model is the Apollo 16, a rackmount interface that supports Thunderbolt 2 and sells for $3,000. If that’s more than you need or can afford, the Apollo Twin Solo (Mac, $699) and Twin Duo (Mac, $899) are much more affordable. (A USB Twin Duo for Windows is also available.) The difference between the Solo and Duo is that the Duo has two SHARC DSP chips; the Solo has one. Either way, the solidly built desktop unit oozes quality. It offers as many as ten simultaneous inputs on the back panel, two analog channels via a pair of combo XLR/TRS jacks and eight digital channels via ADAT Lightpipe I/O. The Apollo can handle sampling rates as high as 192kHz if you can get by with fewer ADAT channels. Alternately, the optical port can carry two channels of S/PDIF I/O, and an instrument jack on the front is suitable for guitar or bass. Two pairs of TRS jacks labeled Monitor and Line Out are on the back, and a 1/4-inch stereo headphone jack is on the front, giving you six channels of digital-to-analog conversion.

A large knob on the top panel controls whichever inputs and outputs you select, and LEDs encircling it indicate input and output levels. Below that, a row of buttons enables the low-cut filter, phantom power, and other functions. The accompanying Console software affords access to all parameters, channels, plug-ins, and signal routing. (Read a review of the Apollo Twin at



The Zen Tour (Mac/Windows, $1,495) is the latest audio interface from Antelope Audio, a company that established itself over a decade ago by producing high-end AD/DA converters and clocking devices. The Zen Tour is a rugged, portable tabletop model that features both Thunderbolt and USB 2.0 connectivity on the back panel. Despite its compact size, it maxes out at 8 analog inputs, 16 analog outputs (depending on how you count them), and 18 digital inputs and outputs.

On the top panel, a bright, colorful touch screen displays all parameter values, channel levels, onscreen buttons, and menus. A large knob alongside the display changes selected parameters, and a talkback button is on hand when you need it. On the back panel, four inputs on combo XLR/TRS jacks can be switched to accommodate mic or line-level audio sources. On the front, four more inputs are on 1/4-inch jacks, and they’re switchable between high-impedance instruments and line-level sources. A pair of 1/4-inch reamp outputs on the front sits alongside two independent 1/4-inch stereo headphone jacks. Around back, you get four TRS outputs for separate monitor pairs and S/PDIF digital I/O on coaxial jacks. Another eight analog outputs on a 25-pin D-sub connector require an optional 8-cable snake if you want to use them. Four optical jacks mounted on the side accommodate ADAT I/O.

One particular feature that stands out is the Zen Tour’s onboard suite of effects. Taking advantage of the onboard 64-bit field-programmable gate array (FPGA) for algorithm processing, the Zen Tour offers amplifier and cabinet simulation, Pultec EQ emulation, and Antelope’s algorithmic reverb Auraverb. In addition, control apps for piloting the Zen Tour from your Mac, PC, iPhone, or Android supply onscreen parameter controls, an onscreen mixer, and a routing matrix.



Unlike the other products in this roundup, the single-rackspace 112D (Mac/Windows, $1,495) has no analog inputs or outputs nor any AD/DA conversion, but it excels at converting between various digital formats. If you need to connect microphones, instruments, line-level sources, or monitor speakers, then first you’ll need at least one external device to convert audio signals from analog to digital and back.

The 112D connects to your computer via Thunderbolt 1 and 2, USB 2.0, or Ethernet. According to MOTU, the 112D is the first interface to combine Thunderbolt, AVB (Audio Video Bridging), and MADI (Multichannel Audio Digital Interface) networking in a single device. Over Thunderbolt, it gives you a maximum 112 simultaneous channels of digital I/O—24-channel AES3 (aka AES/EBU), up to 24-channel ADAT optical (depending on the sampling rate), and 64-channel MADI.

A large LCD on the front displays clock parameters and signal levels for all inputs and outputs simultaneously, and it can display hardware settings and status information at the push of a button or two. All external connections are on the back panel, where you’ll find three 25-pin D-sub sockets for AES3 connections, six pairs of optical I/O ports for ADAT connections, MADI in and out on coax connectors, an Ethernet port for ABV, word clock in and out on BNC connectors, a USB connector, and a single Thunderbolt port.

The 112D pairs with bundled AudioDesk software for controlling all parameters remotely. AudioDesk also furnishes an onscreen mixer with 48 channels and 12 stereo buses. Onboard effects include reverb, British analog EQ emulation, and Teletronix LA-2A compression modeling. Because it’s class compliant, the interface is plug-and-play compatible with Mac OS X, Windows, and iOS. As long as your audio stays in the digital domain, the 112D is an extremely versatile connection between your computer and digital audio devices.



Lynx Audio Technology has been designing and building AD/DA converters and sound cards for audio professionals, musicians, and recording studios since 1998. The Aurora 8 is a single-rackspace converter that supports 16-and 24-bit audio at sampling rates as high as 192kHz. Although Lynx calls it an 8-channel interface, it can stream eight channels of analog audio at the same time as eight channels of digital AES3 audio. Any other manufacturer might call that a 16-channel interface, but all the analog inputs must be routed to either the analog or digital outputs. You can double the number of channels with a hardware upgrade; if you need more to start with, though, check out the Aurora 16.

The Aurora has an LSlot port on the back panel that accommodates expansion cards for connecting to other devices in a variety of formats. In addition to cards for USB, Pro Tools|HD, and MADI (an ADAT Lightpipe card was discontinued in 2014), Lynx’s LT-TB card makes the Aurora 8 a Thunderbolt audio interface, and the model with that card preinstalled is the Aurora 8TB (Mac, $2,195).

The 8TB’s back panel has three 25-pin D-sub sockets: one for analog in, one for analog out, and one for AES3 in and out. (Optional 16.4-foot snakes with XLR connectors at one end are available from Lynx.) The only other connections are MIDI In and Out on DIN connectors and word clock on BNC connectors. Lynx’s SynchroLock word clock is reputed to be particularly stable and resistant to jitter. Buttons of the front panel afford access to parameters you’d change most often, including sampling rate, sync source, and so on, and peak LED meters indicate signal strength for either the analog or digital inputs. You can control parameters in greater detail using Aurora Remote, as well as route signals and view levels for all ins and outs.



Beginning with anti-aliasing filters more than 30 years ago, Apogee has evolved into a well-respected manufacturer of AD/DA converters, audio interfaces, and high-definition clock generators. One of Apogee’s newest products is a revision of its highly respected Symphony I/O converter.

You can choose from Thunderbolt, Avid Pro Tools|HD, or Waves SoundGrid versions of the Mk II, depending on what kind of connectivity your setup requires. The Thunderbolt model supplies two Thunderbolt ports. An option card slot on the back lets you expand connectivity, if needed. Two larger module slots let you configure the Mk II for however many inputs and outputs you need (or can afford). Standard features include a 1/4-inch stereo headphone jack on the front and word clock I/O on BNC connectors on the back.

The Mk II’s touch screen lets you access all its control functions, and the included Apogee Maestro software lets you set all parameters, create custom mixes, and route inputs and outputs using your computer. The Mk II’s base configuration (Mac, $2,495) comes with a module furnishing two analog inputs on XLRs, six analog outputs on a 25-pin D-sub socket (an optional snake is required), stereo AES3 I/O on XLRs, and stereo S/PDIF on coaxial jacks. Optical in and out connectors accommodate either 4-or 8-channel ADAT at rates up to 96kHz or 2-channel S/PDIF at rates up to 192kHz. The 8 x 8 configuration ($3,295) features a module with eight analog inputs and outputs on D-subs, AES3 I/O on another D-sub, stereo S/PDIF on coaxials, optical I/O dedicated to SMUX (high-rate ADAT), and optical I/O that accommodates S/PDIF, SMUX, or ADAT. The module in the 16-channel configuration ($4,295) has 16 channels of analog I/O on D-subs and S/PDIF on coaxials. You can mix and match these three modules in the two slots as needed and your budget allows. In addition, modules from the original Symphony I/O are compatible and available in a variety of configurations.

Windows Compatibility and Expense

Despite its obvious speed advantages, Thunderbolt hasn’t been broadly accepted by the Windows community. Although Windows 10 supports it and Thunderbolt cards are available for PCs, the protocol hasn’t really caught on, and only a few models come standard with Thunderbolt ports. Consequently, not a lot of products specifically support Thunderbolt in Windows, but that’s beginning to change.

Compounding the problem is the unfortunate fact that Thunderbolt drives and cables cost a lot more than they should, no matter what your platform. Fortunately, studio-quality Thunderbolt interfaces don’t cost much more than comparable USB interfaces, making it easier for the audio industry to embrace it as the data bus of choice for professional work.

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