Aune Audio X1S headphone amp / DAC – a review

First off, thanks to Aune Audio for letting me participate in the North America tour of the X1S desktop headphone amp / DAC.

Introduction

Admittedly, I’ve never heard of Aune Audio before I saw the thread announcing the new X1S. That’s not surprising, though – head-fi seems to be exploding at an exponential pace from all corners of the globe. The good thing is that getting into quality audio has never been easier. In a recent SoundStage Access editorial, Mr. Wetzel lamented that the ultra high-end seems to be the ever increasing focus at shows these days. Luckily for the rest of us, there are plenty of companies out there that can see the forest for the trees and give budding audiophiles the chance to experience high-fidelity sound at sane prices.

The headphone amp / DAC under review here is a Swiss Army knife of sorts – it supports nearly every sample rate / bit depth combination on the market today, claims to drive virtually any headphone in existence, and can accept multiple digital inputs as well as output a line-level signal for a connection to a home stereo system or outboard headphone amp. The figurative cherry on top comes in the form of different digital filter options. This would be a tall order for several separate components to execute successfully, not to mention a single one with a value-conscious price target. I think, though, that the folks at Aune have largely hit all the right notes with the X1S.

Description

The X1S is about the size of a small book, though more squarish in proportions. The convex top is a touch of class to what would otherwise be a utilitarian black box. The scooped out sides fit the fingertips neatly, allowing for easy placement on the desktop. The sturdy thick steel shell is fronted by an equally thick front panel with a sensibly arranged bevy of controls and a 1/4 inch headphone output jack. The flush mounted input button also does double duty as the digital filter selector switch. The metal volume knob has a very smooth action and exudes quality.

The back panel is mounted flush to the outer casing, with everything held in place by two long screws. Here we have a laundry list of inputs and outputs – a USB 2.0 type B input jack, optical and coaxial (S/PDIF) digital inputs (and output!), unbalanced analog audio input, and unbalanced line level output. A small rocker switch turns the unit on and off. Curiously, the X1S uses an outboard power supply with a custom umbilical connection. Small red plastic caps are supplied to cover off unused inputs – a nice touch.

Overall, the build quality is superb and marred only by one major flaw – the short length of the cable from the power brick to the back of the X1S. With the X1S on top of the desk, the power brick is left to dangle a few inches off the ground. This was somewhat surprising given the thought and attention paid to the design of the X1S itself.

Rounding out the package is a 3.5 mm to 1/4 inch adapter and a USB cable with gold plated connectors. Software drivers and user’s manual were supplied on small USB memory stick.

Note that the USB connection must be used for the X1S to play the widest variety of sample rates, bit depths, and formats. S/PDIF and optical inputs are bandwidth limited to a maximum of 24 bit / 192 kHz PCM data only. DSD128 is the top end for DSD playback.

Operation

I usually use a Linux system for computer-based audio. In this context, the X1S is strictly plug-and-play, so long as your kernel has the USB audio module compiled and installed. The Aune identified itself as ‘X1S USB DAC’. For Windows-based machines, you’ll need to install the supplied drivers for the DAC to function correctly.

The dual-mode input / digital filter selector button is fairly straightforward to use. A quick push scrolls through the various inputs and the selected input is indicated by a lit green LED. Holding down the button changes the LED color to red and cycles through the different digital filters: linear phase, slow roll-off, and minimum phase. Simply let go of the button when you reach the filter you want. Switching digital filters during playback is supported, though there is an audible mute and delay if you do. The X1S is smart enough to remember your input and digital filter choices should you need to power it down.

One minor gripe is the lack of a sample rate indicator during playback – this can make it difficult to know if you’ve set up your entire playback chain correctly.

Sound

First a caveat – though I do own a fair amount of SACDs, I do not have any DSD files on hand, so my impressions will be strictly limited to the reproduction of PCM-based audio.

Eager to put the X1S through its paces, I powered it up and connected it to my computer. The power-on default seems to be the USB input with the linear digital filter enabled so I left it at that. I then plugged in my Etymotic ER-4Ses, started VLC, and cued up “1234” from Leslie Feist’s third album The Reminder (Cherrytree/Interscope Records, B0008819-02). To say that I was underwhelmed, is a bit of a, well, understatement. The sound lacked life and rhythmic drive. Fortunately, there were still two other digital filters in the stable.

I switched in the slow roll-off filter and played the same track. I heard a subtle improvement – vocals seemed to be more clearly defined. Coltrane’s sax and Kenny Drew’s accompaniment on the piano started to come alive. However, the low end still seemed to lack a little impact and the upper midrange / treble still sounded a touch aggressive.

With the minimum phase filter enabled I felt that the X1S was finally firing on all cylinders. Bass had some heft now and vocals were more fleshed out. The overall sonic signature became more vibrant and saturated. This is the filter I used for the rest of my review period.

If I needed to summarize the overall sonic characteristic of the X1S in a few words it would be this: warm and smooth. This was evident across the board on all the genres of music I listened to. Vocals were full bodied without excessive sibilance. Feist’s voice on “1234” sounded less ethereal or ‘wispy’ and more immediate. Bass had good weight and definition. The picked guitar and plucked banjo had a pleasing combination of tone from the strings as well as the instrument body. Matt Berninger’s baritone on “Pink Rabbits” from The National’s Trouble Will Find Me (4AD, CAD3315CD), was equally satisfying. Drums on both tracks possessed equal parts attack and impact. The Aune also proved adept at reproducing sweeping scale and emotion as evidenced during the final movement of Rachmaninoff’s Piano Concerto No. 2 (Chesky, CD 2, ripped to WAV). The X1S delivered an organic coherency between Earl Wild’s virtuosity on the keyboard and the London Royal Philharmonic. Strings flowed effortlessly and the piano had a pleasing bloom around the notes.

And yet some of those same strengths seemed to ultimately hold the X1S back. Although Trane’s tenor sax, Fuller’s trombone, and Morgan’s trumpet let loose with a burnished, brassy glow on “I’m Old Fashioned” from a hi-res copy of Blue Train (HDtracks, 24 bit / 192 kHz AIFF), the Aune seemed to gloss over the microdynamics – those little intonations and complex overtones that make the performance more expressive and engaging. I also felt that the Aune lacked that last bit of airiness that conveys the sense of performance in a three dimensional space, opting to focus on delivering midrange bloom instead. That last point, I must concede, could be an artifact of my digital filter choice.

These really are tiny nits that I’m picking given the value that the X1S offers. The Aune gets the big picture right. It produces a satisfying sound that is a boon to more modern recordings while doing justice to those albums that were well-engineered.

Comparisons

The reference I use nowadays for computer-based hi-fi is a Meridian Explorer 2 coupled with the AudioQuest JitterBug. When compared directly to the X1S, the Explorer 2 sounds a little more neutral to my ears. Both have good tonal saturation but the Explorer 2 has the edge in the fine detail and spatial resolution department and a bit more rhythmic drive. Yet the Explorer’s cooler palette can prove to be a bit fatiguing on modern rock and pop during long listening sessions. The AudioQuest DragonFly v1.2 (with JitterBug, natch) on the other hand, follows somewhat in the same sonic vein as the X1S. However, the DragonFly tends to sound soft on top and here I feel the X1S pulls ahead with its more even tonal balance and slightly better detail retrieval. I also tried using the JitterBug in concert with the X1S, but I didn’t hear an improvement.

Conclusions

Companies like Aune make it easy and hard for the present-day audio enthusiast. Easy because clearly the X1S is a well-built and great sounding piece of kit. Hard because you’ll be searching high and low for a justification to spend more money on something else given the features and sound quality the X1S has to offer. I think it’s needless for me to say that I’ll be paying closer attention to Aune from now on.

Associated Equipment

Headphones – Etymotic ER-4S, NAD Viso HP50

Loudspeakers – Vandersteen 3A Signature

Amplification – Ayre AX-5 Twenty, CI Audio VHP-1 / VAC-1, AudioQuest DragonFly v1.2, Meridian Explorer 2

Sources – AudioQuest DragonFly v1.2, Ayre C-5xeMP, Meridian Explorer 2

Cables – Analysis Plus Solo Crystal Oval 8 speaker cable, Analysis Plus Copper Oval-In and Pro Oval Studio interconnects, Blue Jeans LC-1 and MSA-1 mini-RCA interconnects

Power / Tweaks – Bryston BIT-15, AudioQuest JitterBug

 

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