ESI U168 XT Review
ESI U168 XT - Click to Zoom
I’m excited to bring this investigative report to you. I admit that I get a little extra bit stoked when an opportunity is presented to bench-test a new piece of hardware. This is certainly one of those times. ESI is not especially well known here in Canada, or anywhere North America for that matter, but I was highly intrigued when the U168 XT press release came across my desk.
Have you seen the ESI press release on Reviewer’s News? U168 XT Press Release As it turns out, German technology builders, ESI, have decided to enter the North American audio interface fray. I’m honored that Reviewer’s Revival is one of the original six entities to have received a demo unit. At 24 bit/96kHz, there is plenty of audio resolution on tap to produce über quality recordings, but since this is a USB 2.0 device, and thus limited to USB 2.0 transfer rates, it won’t take you into the stratospheric 192+ kHz range. I suspect that if you’re using a system powerful enough to handle the incredible amounts of data storage, and CPU capacity, that ultra high resolutions demand, you’re probably using a $3000 “Antelope” HDX interface and Pro Tools HD – in an elite LA Mastering studio. *Wink. The U168 XT is an upper mid-class prosumer peripheral -- compatible with both MAC and Windows PCs. ALL the boxes are ticked with big, bold check marks: build-quality, features, speed, performance, I/O, sound quality and useful appointments. We must keep things “on-the-level”; I have a few shards of neutralizing commentary to share, but for the most part, I’m very impressed with the U168 XT.
This audio interface is a fast, capable device that boasts a full complement of I/O connectivity – free of tangled, light weight breakout cables. We have (16) balanced TRS (Tip Ring Sleeve) inputs, (8) balanced TRS outputs, S/PDIF in/out, (4) high quality mic pres, and (2) high level ¼ inch headphone outputs. All of which are packed into a sturdy metal housing that’s powered up by the included, 12V power supply.
If you’re one of my European neighbors, then perhaps you’re already well acquainted with ESI Audiotechnik. Be that as it may, here in Canada & USA, the brand is not nearly as well known. I admit that when I received the U168 XT & U86 XT press release, my initial thought was that ESI must be a new startup. After a bit of research, I learned that the company is actually well-regarded in Euro-centric demographics, and that they’ve been doing this sort of thing since 2005. Now then, anyone who still needs to rely on USB 2.0 for their audio interface connectivity, please raise your hand. I too am one of those hobbled USB 2.0 folks. My current, new-ish ASUS i7 7700 HQ laptop is a very respectable multi-media/gaming computer, but it doesn’t harness the power of thunderbolt integration. Alas, isn’t it mostly our MAC Book Pro friends whom are outfitted with thunderbolt? Desktop users can install a PCI-e Thunderbolt add-in card, if they have an available slot on their desktop system’s motherboard, and some extra loot to spend. I would be thrilled to bits if I were able to hook up a shiny new “Focusrite Clarett” or “PreSonus Quantum” to my DAW PC(s), but alas, I’m restricted to USB 2.0, USB 3.0, and USB 3.1-C connectivity. As such, I’m all too aware of how necessary it is to have a good quality, fast, reliable USB 2.0 (or USB 3.0) audio interface. Of particular importance is the efficiency of a unit’s device drivers – especially where ASIO performance is concerned. It’s generally agreed that when it comes to USB 2.0 driver efficiency and reliability, RME has been the bar by which all others are measured against. Here in Canada, a new RME “Babyface” will remain proudly displayed on the shelf, behind the music store counter, unless you have $1000 to $1200 extra (CAD) dollars to drop. Let’s face it, unless one is actually earning money as a recording engineer, the average Joe can’t commit to that kind of expenditure for a personal hobby toy. Thus the old adage “you get what you pay for” is indeed true for we home recordists and producers. A recurring cry of many home producers has been for better drivers from all the popular builders: PreSonus, Focusrite, Zoom, Roland, M-Audio/Avid, and etcetera. Some of the developers finally started to listen and have responded to their customers’ needful requests. Case in point, the most recent revision of Focusrite’s USB drivers has made a marked improvement in the performance of my Scarlett 2i4. On the other hand, my PreSonus 44VSL is still lagging far behind and requires much larger buffer settings than the Focusrite unit. The 44VSL sounds great, and boasts high quality mic pres, but it suffers from high latency while tracking.
I made the mistake of clicking on the speaker icon in the Windows task tray . . . frozen.
After a few seconds, I was greeted by my very first Windows 10 BSOD – blue screen of death. Me be a-thinking, “Whaaatt?!” Up ‘til then, my system had been absolutely, flawlessly stable. It was tweaked for maximum DAW performance. Well, being an experienced (ex) professional computer & networking technician, I immediately started trouble-shooting. I won’t bore you with a list of trouble-shooting steps that I’d taken, but suffice it to say, I was thorough. Unfortunately, I couldn’t remedy the issue. I was kinda bummed out – I really was looking forward to experiencing the performance gains promised in the ESI press release. I began having a mutually respectful, open dialogue with ESI Managing Director, Claus Riethmueller, and also ESI’s lead developer, Jesko Q. It turned out to be a little glitch in the giddyup with certain USB 3.0 chipsets. I submitted the details of my Intel USB chipset to Jesko. He and his crew got straight to work, and within a few days, he furnished me with a new beta driver. Lo and behold, this time ‘round, the installation process went off without a hitch. With hesitancy, I apprehensively pressed the power switch. After 45 seconds or so, Windows 10 was pleasantly talking with the new hardware. I excitedly configured the U168 XT’s USB latency, Buffer and Sample rate settings. It worked well and sounded great in each of the four DAWs I’d quickly tested it in. I immediately wrote my kudos and congratulatory comments to Claus and Jesko; thanking them for their due diligence. Claus Riethmueller had this to say in reply: “Thank you for your feedback! I find your observations regarding the quality of the preamps and also (or especially) about the ASIO performance, and probably latency compared to the other products you mentioned, quite good. Let's just say, it does not surprise me that much, as we have put a lot of effort into it -- especially in the design of the analog parts and into a stable power supply for the ADC and DAC converters. Likewise, ASIO performance always has been our strength in the past, for our audio interfaces.”
What’s in the box?
My unit arrived in a securely encased, double-boxed, courier package. After digging the retail box out of a heap of “styrofoam popcorn”, I was immediately impressed with the heft and sturdy, ‘tight feel’ of the box – no slippage or loose, cheap-feeling movement. Although attractive, the box itself has a serious, no-nonsense appearance that eschews any kind of “gussied up” marketing bling. The interior packaging also bore a professional, careful air about it. Everything was neatly arranged and kept together in snug plastic wrapping and good quality adhesive.
Lastly, a USB cable and a 12V power supply are also enclosed. The power adapter itself is a sturdy little AC brick, but the power cable (from wall to power brick) is only about three feet long. Adding to a buyer’s cabling frustration, the USB cable is barely four feet long.
*Rolling my eyes. Seriously? Did ESI have to shave costs by compromising their superb product with skimpy cables? It would have been much more customer-conscious had they included a 6ft. power cord, and a 5ft audio-grade USB cable.
Appointments & Presentation:
ESI’s XT series of audio interfaces showcase classy, sleek lines, rounded edges and professional-looking layouts. Some would say that it bears a somewhat orange-y cast, but more accurately, the unit is handsomely presented in a rich, deep-copper tint. Starting from the front left, here’s what we have at hand on the U168 XT: 
ESI U168 XT (Front) - Click to Zoom
Inputs (1) and (2) are a pair of combi-sockets in which you can connect both low-balanced XLR or high-impedance ¼ inch (instrument) jacks. Channel (1) defaults to the stereo left, and channel (2) to the right. Channel inputs three and four accept XLR-only connections. Each of the four channels features an input gain knob, an off/on (mute) switch, LED metering, and selectable 48V phantom power.
The phantom power assignments are undeniably a cut above, as compared to other audio-interfaces in this class – most do not provide individually selectable phantom power per channel. On the U168 XT, however, each channel has its own 48V phantom power switch – now that’s convenience and usability extraordinaire! The metering is pro-grade. Input signal strength is displayed across a row of three LEDs, spanning -18 dBV, -6 dBV and 0 dBV. Low level signals flash green (-18 dBV), moderate input levels are indicated by a yellow LED (-6 dBV) and as expected, hot signals at 0 dBV or above, come out red. Following the (4) input channels is a small, yet functional, mixer section. Here we have a pair of ‘Mono’ push-buttons, a row of four channel activity indicators, two input volume knobs (channels 1 – 8 and channels 9 – 16 respectively) and an output volume control.
Next in line there are not one, but TWO, amply-powered ¼ inch headphone outputs – each with its own volume knob. There is a pair of push-buttons to select DAW (mix) monitoring or direct monitoring; one for each headphone output.
Lastly, we have a push-button power switch, and accompanying LED power indicator, occupying the right most position on the front panel. Overall, I assess the front strip of this audio interface to be very well laid out and decently proportioned. Regrettably, I do find that the gain and volume knobs are all too small. The controls rotate smoothly and feel very sturdy, but they’re somewhat fiddly to operate due to their meager size. I suppose if you have young, slender fingers, you’ll get along ok, but the small dials don’t suit my big ol’ man mitts very well. *Grin. Under dim lighting, it’s very difficult to see what level a knob is set at. A thin white strip etched into each dial would be very helpful. There isn’t any room to spare on this thin chassis, but I would suggest that ESI’s designers consider making it a little taller, and provision us with a row of sixteen separate input gain pots for all (16) input channels. Flipping the unit around, we find a bevy of I/O ports; covering all common connectivity needs -- and even a few extras not typically found on competing, higher end “Pro-sumer” interfaces. 
U168XT Rear Panel - Click to Zoom
Firstly, a pair of standard MIDI din ports greet us; midi out & midi in, respectively. Next in line is a 12V DC input and standard USB-b port. A duo of S/PDIF ports rest alongside in typical RCA format – offering both input and outgoing connections. A familiar-looking laptop security lock slot is here, closely followed by standard stereo MASTER MIX TRS ports.
Occupying the center of the back panel are the (8) stereo line out (TRS) connectors. Taking up the rest of the back-panel real estate are (16) TRS Input ports.
Performance & Functionality:
One of the first things I was pleasantly surprised by, was the complete lack of obnoxious thumps or snaps when the unit is powered on, or when it’s switched off. Clearly, this indicates exceptional power distribution. Unlike many mid-class USB interfaces, this one is *not bus-powered; it requires a dedicated 12V DC power supply. Personally, I prefer this method of powering a device because it means that my laptop’s USB power will not be consumed by the audio interface. When attached by itself, an audio interface is not a huge energy drain; however, power consumption becomes more of a concern when you’re also connecting a USB midi keyboard, a surface controller, and so forth.
I’ve already extolled the unit’s phantom power virtues, but I’m positively tickled that 48V phantom power is selectable per channel; as opposed to only being configurable globally.
Most audio interfaces, ranging from budget soundcards up to middle-tier devices, are not typically furnished with on/off switches. I really appreciate the convenience of having a power switch right there on the front panel. Kudos, ESI.
ESI hasn’t marketed their mic pres with any sort of catchy, cool-sounding “XYZ” names, but I can assure you that these preamps are some of the best in class. They yield flat frequency response and impressive dynamic range – loads of headroom! What’s more, the instrument inputs don’t easily clip, yet have tons of available gain. I suspect that some type of refined, auto-sensing pad control is hardwired in for us. It doesn’t stop there – the mic pres have a decidedly expensive, “Hi-Fi” quality about them.
There is plenty of hi-fidelity, crystal clear input gain on tap. I haven’t exact measurements for you, but I can tell you that the U168 XT provides substantially more input gain than a Focusrite “Scarlett 2i4” can deliver. I’ve always considered PreSonus “VSL” audio units to have robust, more-than-adequate gain, but this ESI interface serves up every bit as much; perhaps slightly more. As regards frequency response and clarity, I consider the U168 XT to be the most “Hi-Fi” sounding USB audio device I have personally used to date.
Latency Performance:
USB 2.0 busses are capable of reaching data stream speeds of 480 Mbps in *one direction at a time. In real-time performance tests, it’s been noted that most USB 2.0 audio interfaces transfer data at a speed of only 280 Mbps. Unlike USB 3.0’s 4.8 Gbps, which is a full duplex, asynchronous topology, USB 2.0 relies on polling (think narrow, single lane, country roads). USB 2.0 audio interfaces will never be able to operate at the ultra high sampling rates and breath-taking speeds that thunderbolt is capable of distributing. Notwithstanding, USB 2.0 offers extremely broad compatibility and can be accessed on most nearly any computer produced in the last 15 years. It’s not ready to be put out to pasture just yet – well developed USB 2.0 ASIO drivers are capable of providing workable, low-latency timings as small as (2.5 - 3) ms (roundtrip). Albeit, these are optimistic ratings that can be realized on only the latest, most powerful computers – and only with minimal track counts.
I use quite a few midi virtual instruments in my projects; including Kontakt and UVI sample libraries. Let’s not forget the dozens of 3rd party processing plug-ins that many of us like to use in lieu of stock DAW processors. All of the aforementioned, combined with vocal, guitar, bass, and miscellaneous audio tracks, does end up putting a fairly heavy load on my CPU. Hence I typically must use buffer settings of 1024 (or greater) to ensure smooth playback while mixing. Well, at least this is the case any other USB audio interface I’ve used.
I’m deeply impressed that I can experience most nearly the same level of efficiency at a buffer setting of 512 with the U168 XT – utilizing ESI’s version 1.2 drivers. What’s more, I can easily track and natively “real-time” monitor most virtual instruments (including U-He DIVA) using a buffer size of 64 -- without crackles, pops or dropouts. I’ve even managed to use a buffer length of only 32 samples with a good degree of success, but there were occasional hiccups. ** UPDATE ** With version 1.3 drivers, I can run full Studio One Pro (v3.5.1) projects with buffer settings as small as 256 samples, at 44.1kHz. This is a multi fold improvement over ALL my other audio interfaces' performance levels. These same projects require buffers of 1024 samples (or higher engaging PreSonus "Dropout Protection") using my other USB audio interfaces (Mbox mini 3rd gen, Focusrite Scarlett 2i4, and PreSonus 44VSL). Personally, I’m very happy when I can maintain glitch free, real-time monitoring at a buffer setting of 128. This results in roundtrip times of only 5.6 to 7 milliseconds at the most –- more than adequate for “live” recording. Halving that value and lowering the buffer to 64 samples (4.35 - 5 ms roundtrip) pretty much makes tracking and performance “feel” instantaneous to me. The old-timers would say, “Proof is in the pudding.” Here are Studio One Audio Panel screen shots of U168 XT driver/latency performance on my ASUS GL753.
Sound Quality:
Solid. Open. Transparent. Accurate. These terms aptly describe the ‘Class A’ audio quality that’s to be heard here. The U168 XT boasts very impressive analog-to-digital and digital-to-analogue specifications on paper. Quite frankly, I don’t think that the numbers have been embellished at all – if anything, they’re probably more on the conservative side. I haven’t a scientific audio lab full of wizardry tools here in the reviewer’s den, but I do have decent ears. *Grin. Without intending to foster one teensy bit of hyperbole, it seems to me that this metallic slab of audio artistry is a very fine example of German engineering indeed. Clarity is the order of the day here. The U168 XT houses powerful, ‘Hi-Fi’ mic pres, high headroom converters, low noise output, and stable, quiet power supply. In no way does this audio interface suffer from underwhelming, anemic gain and/or volume levels. It produces clean, unerring, powerful output – this applies equally to the Master Mix, the (8) Stereo Outs, and the pair of Headphone outputs. The truth is, this unit could easily be marketed as a top-tier, studio grade device – and priced accordingly. Instead, ESI promote it as an *upper range, prosumer (mid-class) unit. Quite frankly, I think ESI are addressing a very important market segment – making exceptional audio and build quality available without going into the $1000+ range. * I have one very minor quibble. Although the headphone outputs are powerful and very Hi-Fi sounding, the lowest sub frequencies seem to get rolled off ever-so-slightly. ** EDIT ** Version 1.3 drivers have been released as of Aug. 18, 2017. They are working even better on my system. Very stable. Excellent audio quality. I'm hearing the same great fidelity, but the low end is strong (not pronounced). I'm not hearing any sub low end roll off.
Build Quality:
I apologize in advance if anyone thinks I’m being chauvinistic or arcane with this next statement, but I really like the ‘manly’, built-for-the-long-haul appearance of the U168 XT. It’s housed in an anodized metal chassis and attractively presented in a deep copper hue. It’s a solid piece of kit. You can shake it like a Manhattan cocktail, but you’ll not hear (or feel) any rattles. It’s a hefty build – weighing in at around 6.5 Lbs/2.8 KG. Its dimensions are 17.5” long, 5” deep by 1.75” thick (44.45cm x 12.7cm x 4.45cm). All I/O ports, knobs, switches and LEDs feel sturdy and well-fitted. This unit definitely does NOT feel as though it were slapped together in an overrun factory somewhere *overseas – nope! It does, however, feel as though it was built by a team of studious German engineers in a craftsman’s workshop. All U168 XT input connectors are strong and solid. They are constructed of molded plastic - not metal - but they feel rugged, and yield a secure ‘click’ when you insert a cable jack.
Driver Management and Device Configuration:
The accompanying drivers are minuscule. As such, they consume so few system resources that their measurements are negligible. A small system tray icon sits inconspicuously in my Windows’ task tray. I would like to see ESI’s developers release future driver-software that included a larger, easier-to-read control panel. However, it gets the job done and is very light on the system. ESI recommends that end users make configuration changes outside of a DAW. I've found that most of the DAWs on my system can access the U168 XT control panel with relative ease, but as they say: "Your mileage may vary."
Concluding Remarks:
The U168 XT is almost as wide as a 1U 19” rack-sized chassis; wider than some folks would like. Personally, I like “Texas-sized” things. I like big cars, big work benches, big beds . . . big everything. *Grin. I much prefer this kind of sturdy, “everything-at-hand” chassis design over a pretty, petite, square box – that has a tangle-y cable-snake dangling from the back of it. ‘Jus sayin’ . . . However, I understand the attraction towards, and the necessity of, compact audio interfaces -- especially when desk real estate is at a premium. This device is powerful. It produces above-average audio quality. It’s built like a panzer tank. It’s sturdy, sleek and well appointed with a diverse, capable set of features. It provides accurate, gratifying visual feedback in regard to channel activity and signal levels. U168 XT offers boatloads of I/O connectivity. Although I find the knobs and dials a bit undersized, they feel very sturdy. Each dial yields a fluid, ‘just right’ resistance that implies expensive, attention-to-detail. On the software side of things, I’ve noticed that the U168’s WDM drivers are not as robust and reliable as ESI’s ASIO drivers are. Their ASIO drivers are fast and stable. However, processing system audio through the U168 XT using its WDM drivers, has proven to be somewhat flaky for me – notably under higher CPU loads. ** EDIT ** Version 1.3 drivers have been released as of Aug. 18, 2017. They are working even better on my system. Very stable. Excellent audio quality across the board, and very, fast, high performance. * improved performance with WDM/MME audio applications * improved stability with Intel USB 3.0 controllers * fixed some minor bugs * improved level meter display * improved ASIO performance * ASIO control panel button opens control panel For example, I’ve had to exit my video editing application, power the unit off, and restart my computer on a couple of occasions. I’ve chatted with Claus Riethmueller (ESI Managing Director) about this, and he assured me that the team is intently focused on improving their WDM drivers. I believe him. I noticed a nice bit of improvement in the version 1.2 drivers over the beta drivers I’d received earlier.
However, ProSoundNetwork lists an anticipated retail tag of $599 (USD) so I guess we’ll just have to wait and see what the actual tariff will be once North American retailers have some U168 XTs in stock.
* As soon as I have a confirmed cost, I will immediately update this publication. ** EDIT ** As promised, here is the official statement from ESI's press personnel RE. retail pricing: "We are actually going to be able to offer it at a likely street price closer to $499 US … : ) "
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Brother Charles is a freelance writer, Gospel music artist and minister. Charles had been a professional touring musician during the nineties; working primarily as a lead guitarist in the Canadian country music industry. Brother Charles is also involved with music production and quality home recording.
4 Comments
Rev. Marsha Allen
8/10/2017 01:27:10 pm
A very insightful report on this product. I'm sure my sound person will be thrilled to investigate this device.
dirk bruhse
1/22/2018 10:34:44 pm
ITS SOOO SAD ... ESI did a good job BUT they should have build in a cascade-mode to use TWO of the U168XT together to get a 32 channel interface! selling a unit for 100 bugs more woul made it an no-brainer and mega-seller! now I can not use it because 16 ins are much too less :-/
Music Machine Builder
1/19/2022 12:00:26 pm
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