Music Intrusment Reviews

ESI Audio U168 XT USB Audio Interface

ESI Audio U168 XT USB Audio Interface







Feature Reviews

Recording Reviews: ESI Audio U168 XT USB Audio Interface



ESI Audio U168 XT USB Audio Interface

Is orange the new black?



by Phil O'Keefe


harmonycentralesiaudiou168audiointerfaceleader-e6bd0709.jpg.0405f2dd117fb44ab9a7a1f1c0a9dcce.jpgL ots of people start their journey into the world of audio recording with a basic 2x2 USB audio interface - in many ways, this is the modern equivalent of the analog four track reel to reel recorder of the 1970s or the four track cassette recorder / mixer of the 1980s. It's a great place to get your feet wet and learn the fundamentals of audio recording on a computer, and for a lot of people it's as far as they'll ever need to go, since not everyone requires more than two simultaneous inputs. But when buying an audio interface, it's important to carefully consider how many inputs you will realistically need, both now and in the future, and many people will eventually run up against the limitations of a smaller interface, whether it is a lack of MIDI capabilities, or just the lack of sufficient inputs (and mic preamps) to tackle larger projects, such as recording a drum kit or a full band. Germany's ESI Audiotechnik clearly had users who need lots of inputs in mind when they developed their U168 XT audio / MIDI interface. Let's take a look at the details and see what else this cool looking orange box has to offer.  



u168xt-angle-2-db1b101a.thumb.jpg.4227a17a255219ea0a80d57b9d13ee0e.jpgWhat You Need To Know

  • The ESI Audio U168 XT is a USB 2.0 audio and MIDI interface for Mac and PC computers. It's not class compliant, so PC users will need to install drivers. A driver CD is included, but ESI-Audio suggests downloading the drivers from their site instead, which insures you'll have the latest ones for your computer. ASIO 2.0, WDM, MME, and DirectSound (including EWDM and / DirectWIRE), as well as CoreAudio on the Mac, are all supported.


  • Macs need to be running OS X 10.7 or higher, while PCs need to be running Windows Vista or later, with both 32 and 64 bit OS versions supported. Each will also need one open USB 2.0 port. Driver / control panel installation was quick and painless on a quad core 2.0 GHz i7 Mac Mini running El Capitan, and latency was nice and low when running with a 128 sample buffer.


  • A provided "line lump" style 12V DC power adapter is included with the U168 XT, and is required for operation.


  • The ESI-Audio U168 XT is capable of recording at up to 96 kHz, and with full 24 bit resolution. The dynamic range for the A/D converters is 107 dB (A weighted), and 112 dB for the D/A converters. In use it's quiet and neutral sounding, with good fidelity for an interface in this price range.


  • The U168 XT is a stylish looking desktop interface with its orange tinted metal housing. It measures approximately 45 cm W x 14.5 cm D x 4.5 cm H (17.72" W x 5.71" D x 1.77" H), and has black labels for all the jacks and controls. The controls all use black knobs, keeping the orange and black motif consistent.


  • The front panel of the U168 XT has a slightly concave shape to it, with the center slightly recessed.



  • The ESI U168 XT is a 16 x 8 audio interface, with four built-in mic preamps. These are mounted on the front panel. Inputs 1 and 2 offer combination XLR / 1/4" TRS mic / high impedance inputs and can be used for microphones or for plugging in and recording your guitars and bass direct. ESI Audio doesn't say how much gain the mic preamps have, but I'd estimate it as about 55-60 dB.


  • Inputs 3 and 4 have standard XLR inputs without the combo jacks, but are otherwise the same as Inputs 1 and 2. Each of the four front panel inputs has a meter with four LEDs for displaying the input levels, a Gain knob for setting input sensitivity, an On switch to turn the input on (or mute it), and a separate 48V phantom power switch.


  • The rest of the front panel controls are for monitoring. There are two Mono switches. Mono 1 sums inputs 1 and 2 in the monitor mix, while Mono 2 does the same for inputs 3 and 4, allowing you to hear them in both the left and right ears while monitoring instead of panned hard to either side.


  • Three knobs allow you to set the relative monitoring levels for inputs 1-8, inputs 9-16, as well as the eight outputs. These affect the headphone outputs, as well as the dedicated rear panel mix ouputs.
  • Four LEDs are provided that show which of the inputs are being used for input channels 1-4. When illuminated, these indicate that the corresponding front panel inputs are being used, as opposed to the rear panel line inputs.


  • The U168 XT can drive two pairs of headphones at once, and each has its own signal selection switch. These allow you to select between the main outputs 1-2, or from the built-in monitor mixer when the switch is depressed.


  • Each headphone amp has its own 1/4" TRS stereo output jack as well as its own separate gain control.


  • A power switch and power on LED finish off the front panel controls.


  • On the rear panel is where you'll find the rest of the U168 XT's inputs and outputs.



  • The ESI U168 XT has an impressive 16 line inputs on 1/4" TRS jacks. These can accept balanced or unbalanced signals. Inputs 5-16 are always available for line input use, while inputs 1-4 are only available when the front panel inputs are not being used. If you're using one of the first four line inputs on the rear panel and aren't hearing anything, make sure you have the corresponding channel On buttons (located on the front panel) turned off.  


  • You also get 8 Line Output jacks on 1/4" TRS jacks. As with the line inputs, the nominal level of these can be controlled through the ESI U168 XT's software app, and both -10dBV and +4dBu signal levels can be accommodated.


  • The software control panel app is also where you can set the system sample rate, bit depth and clock source, as well as adjust the output mix.



  • If you want to ignore the internal mixer, Line Outputs 1-2 can be used to connect to your stereo monitors. Otherwise, you may want to use the two 1/4" TRS dedicated Mix Output jacks instead.  


  • There are a pair of RCA jacks for stereo S/PDIF digital I/O, and the U168 XT can slave to incoming word clock from the digital input, or serve as the master clock.


  • A pair of 5-pin MIDI DIN jacks provide 16 channels of MIDI I/O, making the U168 XT capable of serving as a basic MIDI interface too.


  • Jacks for power in, and USB round out the rear panel.


  • ESI Audio provides a nice little downloadable software bundle with the U168 XT, including serial numbers and download instructions for Bitwig's 8-Track recording software, Stanton's Deckadance 2 LE DJ software, ampLion Free and GK Amplification 2 LE guitar and bass amp sims, and inTone 2 ESI Edition, which is a multichannel effects processor.




  • Since the U168 XT isn't bus-powered, it's not really suitable as a mobile interface unless you'll be using it somewhere with a AC outlet nearby.


  • While the U168 XT is just about the right size to fit into a single rack space, there are no rack rails included, or even available as an option. Rubber feet on the bottom of the unit make it clear that it's intended as a desktop, as opposed to a rack mount interface.


  • There are no pad switches on the U168 XT.


  • There is no multichannel ADAT digital I/O.


  • While classy looking, the orange and black color scheme makes reading the labels and control settings very difficult, especially in low-light situations. A bit of white paint added to the inset position indicators on the black knobs can help you see their positions a bit easier, but the panel labels can still be tough to read. Fortunately there aren't a ton controls, so you'll probably remember where everything is fairly fast, but in the meantime, keep a light handy. The rear panel, which is black with white labels, is much easier to read, although not nearly as cool looking as the front panel is.





If you need a lot of inputs and outputs on a USB 2.0 interface for your Mac or PC, you should definitely look into the ESI U168 XT. It has enough features to take it way beyond the capabilities of many entry level USB interfaces, including enough onboard mic preamps to do basic 4 mic drum recordings, and with an outboard mixer with multiple direct outputs (or several external mic preamps) you can easily expand it to handle 16 channel recordings, and that's usually plenty for tracking a full rhythm section at once, including drums, bass, guitars and even a scratch vocal. Depending on how many mics you use for the drum kit, you can even track audio from a keyboard at the same time, and with the onboard MIDI interface, you can record the raw MIDI data along with the audio too.


Even better, the unit has very good sound quality at this price point, and it's logically laid out and easy to use. It's not perfect - I do wish there were pad switches on the four mic preamps, and I also wish the unit was rack mountable and had easier to read front panel labeling, but that doesn't at all detract from the plethora of inputs and outputs you get, or the high quality of the construction and sound. This is the first time I've tested out a ESI Audio interface, and it didn't disappoint! While they're well known in Europe, they're less so in North America, and they can be difficult to find. If they keep putting out products like this one, and put them into more stores, I suspect that will quickly change.  -HC-




Want to discuss the ESI U168XT or have questions or comments about this review? Then head over to this thread in the Studio Trenches forum right here on Harmony Central and join the discussion!






ESI Audio U168 XT Audio Interface ($499.95 "street")


ESI Audio's product web page     



You can purchase the ESI U168 XT audio interface from:


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Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.  



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