The X1 Portable Headphone Amplifier by ADL

ADL X1 Front

Anyone who frequents this site knows that there is no shortage of portable DAC and headphone amplifier components entering the space.  One of our most popular [videos on YouTube] follows a trail of 11 (3 more were added later) DAC/Amp combos that shuffled their way through the lab here.  Most units found their niche within the lineup, all of them sounded good, some sounded great, but none of them at the time offered quite the diverse feature set that the new ADL X1 by Furutech brings to the table.

Furutech recently introduced two new personal audio products into the market, the H118 headphone reviewed [here] and then the complimentary DAC and amplifier the X1 ($480).  The features are deep, especially compared to many of the more simplified solutions that have been introduced in recent years. All the ins and outs are enough to make your tech-loving heart skip a beat.  First and foremost, it is fully Apple compliant (even with the new smaller jack), so you can upgrade the sound from your favorite iDevice with little to no hassle. The full-sized USB input allows for a simple solution for connectivity, no extra cables or adapters to buy.  ADL also makes smaller, custom cables for attaching an external source in case you want to clean things up a bit. Connecting to the “Big A” is nice, isn’t exclusive to the X1.  Where the product really starts to diverge from the rest of the crowd is the collimation of everything else that is included. The digital input from both the Apple USB and mini USB (for computer use) can be converted to an analog line out or a digital optical output.  This allows the unit to act like a true external DAC from all angles. The headphone amplifier can even be accessed independently from the DAC via the front facing analog input.  There are even two headphone outputs, one on the front and one located in the rear.  ADL recommends using headphones with similar impedances for best results.

ADL X1 Bottom

The build of the unit is more of what you would expect from a large scale operation like Apple or Logitech.  The size and feel is surprisingly phone like, but perhaps even a bit better considering the trend toward plastic construction in cellphones as of late.  The black machined finish on the top is quite handsome and the back and sides are covered with a durable feeling rubber-and-plastic-like material that reminds me of the HTC EVO phone I had some years ago.  Its footprint is roughly the size of an iPhone and the height is just barely large enough to fit its classy analog volume control knob. This rotate-to-turn-on knob bears a silver-shiny alpha logo underneath a clear polish, a nice subtle touch if you ask me.  It feels durable in the hand and not overly weighty; so carrying it around strapped to your portable source should be fairly worry free.  The top main panel is embedded with small, spaced out indicator lights that let you know what resolution your music is, but not the bit length.  The X1 handled every traditional media type I threw at it perfectly, but doesn’t currently support playback for the audiophile’s budding audio file DSD.  The lower right corner of the X1s underbelly features a very important input switch for selecting either the Apple or USB input. I found the recessed tab to be a little out of the way when the unit is lying flat on a desk. Although this switch initially eluded me, the design here didn’t prove to be cumbersome in execution once was able to locate it.

ADL X1 Back

Power from the X1 is quite substantial for most headphones.  That being said, the most power-hungry headphones might push the amplifier close to its limits. The Audeze LCD-3 didn’t run into any issues.  Even the 300 ohm Sennheiser HD650 I had on hand paired quite nicely with plenty of kick and power to spare. On the other side of the spectrum, the few pairs of extremely sensitive IEMs I ran though the system did reveal a slight hum, but nothing that wasn’t easily covered by normal listening levels.  The design of the X1 seems to originate as a perfect pairing for the companies own H118, so it seems natural that headphones close to the same specs would hit the large sweet spot of the headphone amplifier.

Thankfully headphone amplifier outputs don’t tend to vary nearly as much as actual headphone performance does.  Sure power output can change from unit to unit, but most of the devil is in the details with amps.  Likewise, relative dynamics fluctuate occasionally, (as well as a surprise bass boost here and there) but for the most part frequency response is usually fairly consistent across upper tier portable units where the X1 lands. The broader variable at play here is transparency, soundstage and focused imaging.  The X1 performed effectively across all three fronts. Its small casing didn’t correctly reflect the big sound it produced.  Through the Audeze LCD-3s everything was placed were it should be along the sonic stage.  Listening to The Dead Weather’s I Cut Like a Buffalo single, the impact from Jack Whites upfront drumming was powerful and punchy.  The dual organ sounds that grace both channels were easy to differentiate from each other along the stereo field. Like some of ADLs full-size headphone amplifiers, the X1 leaned towards a more laid back approach that is very easy to listen to. When it was placed side by side with the comparably priced ALO International, I thought the International had the edge in the amplifier section, while the X1 had a slightly better DAC section.  Plugging one into the other yielded the biggest sonic fruit.  Once again versatility reigned supreme, and for a portable unit that is really where the X1 shines most.  Its robust display and input/output capabilities make it stand out among its equally priced portable peers. Even as a whole, the unit is still fully capable of creating output that goes toe to toe with the rest of the top tier portable hifi crowd.

ADL X1 Top


The ADL X1 has done its best to properly earn the title “Jack of all Trades” in the portable amplifier realm.  A full feature set of ‘puts (both in and out) make it an excellent pick for those with diverse needs while on the go.  Its build is both functional and sturdy, which are two very important characteristics to consider when evaluating portable audio. The other is undoubtedly sound quality, of which the X1 is equally adept.  I recommend giving it an audition if you have the chance; the ADL team has done a fine job with their first entry into the portable realm.