Review: Practical Devices XM5
portable headphone USB DAC/amp
www.practicaldevices.com
retail price of review component: $235
- download a printable 11-page PDF version of this review (right-click the link & save target)
Intro
In recent months, the portable USB DAC/amp market has grown to unleash a frenzy of new toys to play with, enough that trying to pick from the options in this arena can be confusing. The new XM5 from Practical Devices at $235 doesn't do much to alleviate the situation - yet another USB DAC/amp? What does this new one bring to the table? I'll try to answer that in this review.
Thanks to Practical Devices for providing the sample loaner unit used for this review.
I previously reviewed the Practical Devices XM4 amp for StereoMojo.com in August 2007 here: Practical Devices XM4 Review, Heaphone amplifier
Reviewer Biases & Process
I primarily listen to home-based, AC-powered amps as that's where most of my personal interest lies, but in my Head-Fi journey since 2006, I have taken up a side interest in portable amps as well and have heard a variety of them to date. All of the portable amps that I have heard in quiet conditions are listed in my profile on Head-Fi.
My standard listening goal for all equipment, portable or not, is a hope to derive as much aural satisfaction from it as possible. As is evident from my profile, my ears have gone through many headphones, amps, and source components. While my hearing is an ongoing self-training, it has grown since 2006 over the course of listening to a wide array of equipment ranging from the low-end to the high-end that I have either owned, or been loaned, or have heard in quiet conditions at mini-meets.
I also believe in "Source First" as a listening methodology and that, in general, solid-state amps should not introduce their own sonic colorations into the signal path. I do, however, recognize that some solid-state amps are designed to have a sonic signature of their own, and in that case, I generally try to review an amp on its own sonic merit.
My Review Process (feel free to skip if not interested in reading)
The review process of any component that I review typically lasts at least 8 consecutive days. The first day I'll spend about 3-5 hours to form basic initial impressions. I'll then take the following 3-7 days (depending on timeframe allowed if a manufacturer loan) to listen actively and inactively. I'll then finish off my listening over 2-3 days to form final impressions and will also do intensive comparisons against other components during this period.
My writing process begins during the 3-7 day listening period when I start taking notes. I start writing after all listening has been completed and will take 1 day to translate all notes into a "beta" review - this usually takes 2-5 hours. The following day I'll read what I've written for content and major edits. After this editing is done, I'll check the review for syntax, sentence/idea structure, and format & flow. Once I'm satisfied, the review is considered done and saved into a personal archive.
Time spent for this XM5 review: 60-70 hours (due to product type I was able to listen to it at work on my laptop with 3 closed headphones and 1 IEM, in addition to at home).
Associated Equipment
Digital sources:
- Plinius CD-101 CDP w/ Signal Cable Silver Resolution Reference power cord, iAudio X5 (DAP), Asus Z71V (laptop PC)
RCA-mini Interconnect:
- Signal Cable SilverMini
Headphones:
- AKG K701 re-cabled w/ SAA Equinox
- Audio-Technica ATH-AD2000, ATH-ESW9, & ATH-ES7
- Denon AH-D2000
- Klipsch IMAGE
- Grado RS1
- Sennheiser HD650 re-cabled w/ SAA Equinox
Comparison USB DAC/amp:
- HeadRoom 2006 Total Bithead
Evaluation CDs
A Fine Frenzy - One Cell In The Sea
Alison Krauss & Union Station - So Long So Wrong, New Favorite
Kelly Sweet - We Are One
Laika - Good Looking Blues
Orbital - The Altogether (Disc 2)
Porcupine Tree - In Absentia
Renee Fleming - Thais
Sarah Brightman - The Andrew Lloyd Webber Collection
The Crystal Method - Community Service II
The Prodigy - Fat of the Land
Thievery Corporation - The Cosmic Game
Wynonna - The Other Side
About the XM5
The Practical Devices XM5 is the company's latest product in a line of headphone amp products that started several years ago with the original XMoy. The XM5 combines a headphone amp with a USB DAC for a true all-in-one DAC/amp unit. Its default op-amp is the TI OPA134, which is rollable to the AD8397 w/ DoubleCat. The buffers paired with this op-amp are the TI BUF634. Rail splitter is the TI TLE2426 in the virtual ground. Capacitors are high-value Electrolytic, Tantalum, and Ceramic. There are two colors available: silver w/ blue front panel, or all-black.
Technical specifications as listed on Practical Devices' Web site:
- Weight: 157 grams (5.5 oz) including alkaline battery
- Power Source: Lithium-Ion Rechargeable System, 9-volt Alkaline, or 9.6V Lithium Non-rechargeable
- External Power Supply: Optional Lithium-Ion Charger
- Battery Charge Time (approximate): Lithium FastCharge System: <1.5 hours
- Battery Life (approximate): Alkaline: 50 hours, Lithium-Ion: 40 hours, Lithium NON-rechargeable: 100 hours
- Maximum Gain: +20.6 dB (gain boost enabled), +12.7 dB (gain boost disabled)
- Frequency Response (20-20,000Hz, typical): +0.1dB, -0.4dB
- -3dB Point (typical): 21 kHz at top end; 9 Hz at low end
- Total Harmonic Distortion (typical): 0.0007%
- Intermodulation Distortion (typical): 0.005%
- Signal to Noise ratio (20-20,000Hz, typical): 103dB
- Dynamic Range (20-20,000Hz, typical): 103dB
- Bass Boost: +6dB @ 100Hz when enabled
- Treble Boost: +3dB @ 10kHz when enabled
- Crossfeed: Active, User-adjustable from mono to stereo using potentiometer; User can bypass using pushbutton
- Auto Power-OFF: user-selectable 1, 3, or 6 hour poweroff interval, or can be set to stay on indefinitely
- Status Indicators: two LEDS (one blue, one amber)
- Integrated Voltmeter accuracy (typical): ±100mV
- Mechanicals: Anodized aluminum case; Glossy laser-anodized faceplate; Polished aluminum volume knob; FR-4 dual-layer PCB with 1 oz. copper
- Other Features: Flashlight Mode: Turns on both LEDs to full brightness; Dimming mode: Allows user to optionally dim the blue LED; Fully configurable amplification and buffering using gold-plated sockets.
- USB DAC: 44.1/48kHz, USB 2.0 Compliant; Native compatibility with Windows XP, Vista; MAC OSX, OS9; most Linux installs
The XM5 ships with all accessories that you need to start using it immediately: an Allen hex key to open the amp, stick-on rubber feet, velcro stick-on dots, user manual, a 6" USB-mini cable, and an AC charger. At the time of this review, a 4.75" gold-plated mini-mini interconnect is also included at no extra cost when ordering new from Practical Devices.
Practical Devices recommended 8 hours of burn-in for the XM5 so I applied it before starting any listening.
Form & Function
As the latest product from Practical Devices, who's been making portable headphone amps for years now, the XM5 has a bit of a legacy to live up to. While I haven't heard the Practical Devices products prior to the XM4, I went into the XM5 with a small set of expectations, from a functional and operational point of view.
The basic physical design of Practical Devices products has remained consistent over their line so far, which is good - the XM5, like its predecessors, sits inside a basic Hammond enclosure fitted with a custom front panel. While a Hammond enclosure might be a bit of a retro throwback in 2008 (considering the recent spate of competitors using a variety of custom enclosures), it gets the job done. It might not look as aesthetically attractive as other competing products, but it's certainly not terrible looking, and you can rest assured it'll survive most physical situations.
In terms of operation, the XM5 is highly intuitive with clearly labeled buttons for Crossfeed, Bass Boost, Treble Boost, Gain Boost, and a 75 Ohm Resistance option. The push-button action is solid, and the buttons are spread far enough apart making it unlikely you'll accidentally press down two of them simultaneously. As for the input and headphone jacks, those are nicely spaced separately by themselves with no layout interruption, unlike the previous XM4 amp, which put the Bass and Treble buttons in a very inconvenient, interrupted layout that required pinpoint pushing due to their placement between the volume pot and the input/headphone jacks. Kudos to Practical Devices for revamping the layout into a form that makes much more sense and is easier to deal with.
The XM5's feature set goes past the already feature-packed XM4 to make it far and away the most feature-packed product in the portable USB DAC/amp market. As just mentioned, it has options for Crossfeed, Bass Boost, Treble Boost, Gain Boost, and 75 Ohm resistance. Of course, the XM5 is also a portable USB DAC which adds that functionality. And finally, like its XM4 predecessor, the XM5 contains a microprocessor that handles power management duties. The use of this microprocessor allows you to set the XM5 to turn on for 1 hour, 3 hours, 6 hours, or indefinitely (until the battery runs out). As this indicates, the XM5's battery powers everything and does not recharge over USB - only the included AC adapter recharges the battery.
Crossfeed, bass boost, treble boost, gain boost, and the 75 Ohm resistance all proved to be very useful options and most people who might choose to activate one or more of them should be pleased with the results. Yes, it's possible to activate all five buttons at the same time if you really want to, but of course that's not recommended. Not only does it shorten battery life, but I tried it - and the results weren't exactly ideal. Gain boost/75 Ohm resistance and bass/treble boost both effectively neutralize each other, making those two simultaneous options pointless.
If it weren't for the inclusion of the 75 Ohm resistance option, I would right now advise against using the XM5 with low-impedance headphones and IEMs. When this was disabled, the volume control over low-impedance headphones simply wasn't ideal and they got too loud too soon. When enabled, low-impedance headphones were much more easily controlled that it wasn't frustrating. Kudos to Practical Devices for adding this option in!
On the flip side, +8 dB gain boost proved to be only necessary for inefficient >300 Ohm headphones. With it disabled, the XM5 easily pushed the AKG K701 and Sennheiser HD650 to loud levels. In fact, there was still plenty of headroom left on the volume pot.
Bass and treble boosts did exactly what they're supposed to do. Treble sharpened up to near metallic and teeth-gnashing with its boost enabled, while bass got a very satisfying added thump in the approximate 50-80 Hz region. These options are of course best enabled on headphones that benefit from this sort of equalization. The bass boost worked well on the AKG K701 and Grado RS1 (with bowls), while the treble boost worked better on the Sennheiser HD650 and the Audio-Technica AD2000, ESW9, and ES7. However, it should be noted that the bass boost affects the mid-bass, and the treble boost affects the lower part of the upper treble. Neither added to their respective approximate extremity points - the treble boost clearly did not make upper treble more decimating in the 12-18 kHz range, and the bass boost clearly did not add any lower rumble or "buzz" in the audible 30-40 Hz region.
Crossfeed worked well enough to simulate a fair sense of soundstage on the Audio-Technica ESW9 and Grado RS1. As this is a very subjective area, I'll merely say that results will vary depending on the headphones being used, and that I really only recommend it on headphones that don't already throw much of a soundstage. The K701, for example, did not really benefit from it, as it seemed to collapse the K701's inherent soundstage. But it's still a useful feature and worth exploring depending on your headphones. And of course it's variable, so you can tune it to any amount that you want, all the way to a mono-channel setting.
Finally, the power settings proved to be very useful. While I didn't test this aspect with the previous XM4 in an amp-only setup in my StereoMojo review, this feature was a lot more useful with my laptop computer setup. Indeed, the power setting may very well be one of the most convenient features of the XM5 when used as a USB DAC, as it allows you to tune it in time to the battery life of your laptop computer or other USB source. The 3-hour and 6-hour settings allow it to be approximately matched up with almost any common battery life today. I did drain out the battery more than once though, so it didn't run all that long (less than 20 hours), but the XM5's low-battery LED lights up when it's almost depleted, making it unlikely that it'll be actually depleted in real-world usage (I ignored the LED and drained the battery on purpose). Although I neglected to time the low-battery LED, I would definitely say that it turns on within less than 1 hour of total depletion.
Listening Environments
I listened to the XM5 in three setups:
(1) As an amp lined out from the iAudio X5 DAP.
(2) As a DAC/amp connected to my Asus Z71V laptop computer, and compared to the HeadRoom 2006 Total Bithead.
(3) As an amp lined out from the Plinius CD-101 CD player (my main reference).
The listening from the iAudio X5 was brief. It did not provide any conclusive useful listening impressions. As iAudio X5 owners will know, this DAP tends to sound better directly from the headphone jack. I can only say that the XM5 worked well enough in this role.
In the laptop setup, files were in lossless FLAC, played back with Foobar2000 0.9.5.1, and output over ASIO4ALL V2. All software volume sliders were maxed out to avoid any software-based attenuation. Note: a software-based Loudness option showed up in the Windows KMixer when the XM5 was plugged in. This option repeatedly auto-enabled itself when the XM5 was plugged in at various times and I had to manually disable it.
In the Plinius CD-101 setup, the XM5 was directly compared against the HeadAmp AE-2 using the Signal Cable SilverMini RCA-mini interconnect.
All CD tracks referenced in the next section were directly A/B'd twice in both their Redbook CD and digital file formats for a comparison of the D/A conversion quality of the XM5's USB DAC versus the Burr-Brown PCM1704 DAC (plus analog output stage) in the Plinius CD-101. Using FLAC+ASIO on the laptop ensured a valid comparison of the DACs between the XM5 and CD-101.
XM5 vs itself - DAC vs amp
Due to its dual nature, a USB DAC/amp allows itself to be used as a total digital/anlog solution, or as just an amp only, so I compared the XM5 in this way - as the USB DAC/amp that it is, and in amp-only form off my Plinius CD-101. This comparison can also be seen as putting the XM5's USB DAC up against the Plinius CD-101's PCM1704 (plus analog output stage) as the constant being kept here is the amp section of the XM5, which is why I refer to "XM5 DAC" and "Plinius DAC" below.
In short, there was no contest here. The XM5 sounded way better in every way in amp-only form with my Plinius CD player than it did as a USB DAC/amp, showing that its USB DAC limits its performance in that mode.
On Kelly Sweet's "Ready for Love" from her CD We Are One, the background details were more prominent with the Plinius DAC, most notably the piano, as there was greater presence to it. The Plinius DAC also sounded more graceful and fluid, whereas the XM5 DAC sounded like it was being "directed" about by an unnatural force. On this track, Kelly's voice was also firmly positioned and planted on the Plinius DAC, while there was an odd modulation type effect on the XM5 DAC - her voice seemed as if it was moving back and forth from slightly left to slightly right in the soundstage. This was highly noticeable on the K701 and even moreso on the AD2000. In addition, Kelly's voice was more direct and upfront on the Plinius DAC, while it was slightly recessed on the XM5 DAC. On another track on this disc, "Dream On", the Plinius DAC was simply richer-sounding, as it sweltered with much more musical information, most of which contributes to the heart & ambience of this track. The Plinius DAC also sounded more diffuse and less concentrated than the XM5 DAC, with a clearer picture of the individual musical elements "suspended" in the sonic image. The XM5 DAC, on the other hand, provided much more of a concentrated, "dissolved" image where the musical elements did not sound clear and discrete.
On Alison Krauss & Union Station's "It Doesn't Matter" from So Long So Wrong, the XM5 DAC was noticeably slow and didn't really get the fast movement squeaks and string taps on the opening notes. On good equipment, you can hear various physical movements (including something squeaky) on the opening 30 seconds or so, along with a clear tapping on the strings that one band member is doing to his instrument, but this barely came across on the XM5 DAC. The Plinius DAC was also very airy, open, and expansive on this track, almost as if the venue were an auditorium, while the XM5 DAC caught much less venue air that it sounded more like a studio. The notes from the double-bass were not very strong and deep on the XM5 DAC either and didn't leave an impression of being anchored very well. The Plinius was also more dynamic, as it effortlessly caught the modulating volume levels of both Alison's vocals and the soft-to-moderate levels of the band as they surround her voice. The XM5 DAC had a tendency to make the volume of each musical component more equal relative to each other, and it did not reveal the softly-rolling dynamic contrasts that the band provides throughout the track.
The XM5 DAC continued to underwhelm with two more AKUS selections, "The Lucky One" and "Take Me For Longing" from New Favorite. The Plinius DAC simply sounded more like music. "The Lucky One" was full and expressive, with plenty of detail on all counts. There was lushness to Alison's voice, along with air around it too. The bass rhythm was deep and anchored, and there was a huge step forward in the transients with the Plinius DAC - the XM5 DAC was simply too soft and dull-sounding. "Take Me For Longing" gave an even better picture of the contrast, as the XM5 DAC made the band sound more like they were half-dead or asleep. The Plinius DAC was a huge step above, as the band just swung around way more and sounded alive rather than half-dead. The comparison was nearly night versus day - on the Plinius DAC, the banjo had way more energy and groove (and a metallic sheen too), Alison's voice was forward and prominent, and there was bite and snarl. There was also a big expansion in the ambient space for increased spatials.
DAC Mode - XM5 vs Bithead
This was a relatively short listening comparison. The two USB DAC/amps were on mostly equivalent footing for the most part, though the XM5 did come away with the upper hand. This was my first time listening to the Bithead with FLAC over ASIO (until this review I'd only heard it in MP3 over Windows KMixer), and it sounded very good actually. The mid-range was nicely full and warm, with good solid bass performance, decent soundstage width, and no serious lack of detail.
The XM5 also gave a nice and full mid-range, about on level with the Bithead. Bass, however, was not entirely fully anchored on the XM5, as it tended to lose control on very deep, loud bass notes at higher volumes. The louder the bass notes the more it tended to lose control, as they got slightly wobbly. Granted, this only really showed up at high volume (but not excessively high, merely loud), and at anything less than high volume it was perfectly fine - good, deep, controlled bass. The Bithead, on the other hand, had a better anchor on the bass at high volume, except it tended to get excessively boomy. So there was a definite trade-off between the two - boomy bass on the Bithead, or uncontrolled, wobbly bass on the XM5, and again, only at high volume.
With none of the buttons activated, the XM5 ended up sounding pretty similar to the Bithead otherwise. In other words, neither was really a stellar performer as a USB DAC/amp, though the XM5 did do slightly better in some areas. It was slightly more detailed for one, and soundstage was slightly wider. But the main advantage of the XM5 was a fuller, more expressive mid-range that made it sound "sweeter," whereas the Bithead failed to draw in much emotion. A somewhat more musical sound, essentially. And of course, the XM5's sound can be tweaked through the Bass and Treble Boost buttons, which propel it above the Bithead which has only crossfeed.
However, as described in the section above, the XM5 opened up way more as an amp over its USB DAC/amp combined sound.
Amp Mode - XM5 vs AE-2
The amp section of the XM5 was compared to the HeadAmp AE-2 on the Plinius CD-101 using the Signal Cable SilverMini as interconnect.
On Porcupine Tree's "Wedding Nails" from In Absentia, and with the Grado RS1 headphones, the XM5 and AE-2 traded roughly equivalent blows. The XM5 was the less bright and less metallic-sounding amp, and it provided a more realistically small soundstage as well, as the band sounded closer for a more intimate presentation. There was also more mid-range meat on this track with the XM5 that fleshed out the various layers, including the guitars. However, the AE-2 had the upper hand on more aspects - it displayed faster attack and caught more transient information, allowing it to give proper bite and crunch on the dual guitars for example. Also, while the XM5 did make the guitars sound less metallic, the AE-2's portrayal was more detailed, as the metallic sound seemed to be part of their texture. The AE-2 also had more energy and better separation of layers, making it easier to hear the individual instruments. It was also more open-sounding and did not limit the band to sounding like they were stuffed up, as the XM5 did.
On Wynonna's "Troubled Heart and a Troubled Mind" and "The Wyld Unknown" from The Other Side, again with the Grado RS1, the XM5 balanced out the RS1's signature more than the AE-2. It gave more mid-range swarth overall, and drew out the backing instruments to sound full, heavy, and long, with plenty of presence and weight. The AE-2 sounded downright disembodied in comparison. The soundstage with the XM5 was also small and intimate for a good realistic portrayal. The AE-2, on the other hand, while not as nicely complementary with the RS1, was superior to the XM5 most noticeably in the areas of PRAT and treble. It was more light-footed and energetic, and conveyed the up-tempo insistence of both tracks far better, as it was just that much more quick and toe-tapping. The AE-2 also gave proper snarl to the guitars and overall simply sounded more "electric." The lively spark of both tracks came fully across on the AE-2, whereas the XM5 lost much of it.
Renée Fleming's recording of Thais, in "Je n'ai pas plus choisi mon sort que ma nature!" from Act 2 Scene 1, is well-recorded and contains one of the greatest operatic dialogues in Romantic-era classical. It takes some serious equipment to get this track right, and neither the XM5 or the AE-2 did. The AE-2 got closer though, as the XM5 didn't punctuate Renée's dramatic vocal bursts nearly as much (and the AE-2 itself didn't do that much punctuation either, at least in comparison to other amps I've heard), and it lost some control over her voice too, taking away some of her vocal power. The XM5 was not as quick on the cymbals as the AE-2 either, just missing the initial stick-impact and tizz, for an incomplete portrayal. And it did not hold the rolling lyrical passages as well as the AE-2 either. The AE-2 did itself struggle to hold onto the dynamically-shifting lyrics, but the XM5 just couldn't seem to stay with the dynamic contrast, and as a result the lyrics didn't roll or swell on it.
Sarah Brightman's version of "All I Ask Of You" from The Andrew Lloyd Webber Collection went better for the XM5 than Thais did. The XM5 had a bolder, slightly richer, more harmonic tonality, that fleshed out the orchestra and two vocal parts nicely. There was no major loss in detail with it either. True to the AE-2's nature though, the vocal parts emerged from deeper in the soundstage on that amp, and the orchestra sounded more sweeping on it thanks to greater air span. The violins were also more separately delineated with the AE-2, and sounded more like a collection of multiple violins with it, where they were more converged on the XM5.
The title track from Alison Krauss & Union Station's So Long So Wrong is one of my standard acoustic references for listening to overall frequency balance and soundstage positioning, along with female vocal portrayal. The XM5 recovered a bit here, with a good strong and prominently bowed-out presentation. Bass was rich and deep on it, and the mid-range was very noticeably filled out compared to the relatively thin-sounding AE-2. Lots of "meat on the bone" so to speak, and it was very nice-sounding overall. Instruments were positioned closely for a realistic venue feel, and even more with Alison's voice, for a somewhat "personal" presentation on her voice. The AE-2 took the upper hand here most noticeably with a more ethereal quality to Alison's voice, faster transient response on the banjo, and higher-quality, textured bass. The XM5's bass did have more quantity though.
Laika's "Widows' Weed" from Good Looking Blues is one of my standard electronica references for testing clarity, detail retrieval, and soundstage precision. The XM5 for the most part fell flat on this track, compared to the AE-2. The bass line, which isn't even all that deep, was fuzzy and indistinct on the XM5. It didn't have the snap-to-grid focus of the AE-2 either, as the various working layers were blurry and unclear. The moving layers that are supposed to drift fluidly between channels, did not on the XM5. There was no sense of ease and fluidity on it. Notes did not appear from a truly black background on it either - there was a slight sense of a gray background with it, as there was no ear-popping vibrancy. Treble wasn't quite as clean and fast as the AE-2's, and to top things off, the XM5's small concentrated soundstage seemed like a large-scale detraction from the AE-2, which was much more diffuse and dispersed. The AE-2 conveyed much more free-roaming air and space that is evident on this track, and it had the greater soundstage width too, with further displacement of left from right.
Thievery Corporation's "Holographic Universe" from The Cosmic Game was next on the plate for a brief test of bass definition, but the XM5 paled next to the AE-2 here. The insistent, driving bass rhythm was not distinct on it and was nearly one-note in pitch. There was not much tone to it either, it was very generic-sounding.
For a true bass test though, The Prodigy's "Smack my B**** Up" from The Fat of the Land is more like it, and it's here where the XM5 finally ended up delivering more than the AE-2, mainly in the area of quantity. It gave a plentiful, satisfying, focused boom and thump, with more force and more power. A harder overall impact. The XM5 did add its satisfying mid-bass to the AD2000 too, which made this track that much more bass-heavy. However, the XM5's lack of speed was highly noticeable on this headphone, and the various elements that should pop, mostly didn't. In addition, the XM5 did not match the Audio-Technica AD2000's bass extension to provide much in the way of low rumble and visceral force. "Fuel My Fire", the last track on this disc, opens up with an active, deep, and low-firing layer, most of which was lost on the XM5. It just couldn't serve up this low bass with much power and instead tipped the scale with more mid-bass output than low-bass.
In a final test, Orbital's "Bigpipe Style" from The Altogether (Disc 2) completed the picture of the XM5's bass quality. Compared to the AE-2, the XM5 had the more massive-sounding bass and threw around more punching-ball force, along with a more down-and-dirty attitude. The AE-2 was leaner yet more controlled and refined, and gave more bass texture.
vs the HeadAmp Pico?
It's probably the question many have on their minds - can the XM5 hang with the HeadAmp Pico? While I can't conclusively answer this due to not having heard them at the same time (I sold my Pico before I received the XM5 review sample), I did extensively listen to the Pico for more than 60 hours just before I went into the XM5.
My short answer is that the HeadAmp Pico is the clearly better sounding product, but you'll pay more than twice the amount of the XM5 to get one. The Pico also has a much smaller feature set (really, almost none, save for the two-way gain switch). It's up to you to decide if you want to spend $500 for a better-sounding USB DAC/amp but with fewer features (not to mention the Pico's highly fingerprint-prone chassis as well).
Conclusion
The Practical Devices XM5 is a decent value at $235 for a USB DAC/amp, but I found it limited by its USB DAC, as it opened up much more as just an amp. It's still a definite upgrade over onboard laptop sound, somewhat on level with HeadRoom's 2006 Total Bithead, so it's perfectly acceptable-sounding and it may be a good solution for the mainstream of budget-fi rigs. The main detraction I found with it was a range of sonic omissions when used as a USB DAC. It's a fine product for non-demanding listeners but I would recommend that serious, critical listeners with revealing headphones look elsewhere.
Practical Devices has certainly done a fine job in the XM5, and in most ways it is a step above the previous XM4. I did not get to evaluate it with a supplied Analog Devices AD8397, though I would've liked to do so. I suspect the AD8397 would take the XM5 even further as an amp.
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portable headphone USB DAC/amp
www.practicaldevices.com
retail price of review component: $235
- download a printable 11-page PDF version of this review (right-click the link & save target)
Intro
In recent months, the portable USB DAC/amp market has grown to unleash a frenzy of new toys to play with, enough that trying to pick from the options in this arena can be confusing. The new XM5 from Practical Devices at $235 doesn't do much to alleviate the situation - yet another USB DAC/amp? What does this new one bring to the table? I'll try to answer that in this review.
Thanks to Practical Devices for providing the sample loaner unit used for this review.
I previously reviewed the Practical Devices XM4 amp for StereoMojo.com in August 2007 here: Practical Devices XM4 Review, Heaphone amplifier
Reviewer Biases & Process
I primarily listen to home-based, AC-powered amps as that's where most of my personal interest lies, but in my Head-Fi journey since 2006, I have taken up a side interest in portable amps as well and have heard a variety of them to date. All of the portable amps that I have heard in quiet conditions are listed in my profile on Head-Fi.
My standard listening goal for all equipment, portable or not, is a hope to derive as much aural satisfaction from it as possible. As is evident from my profile, my ears have gone through many headphones, amps, and source components. While my hearing is an ongoing self-training, it has grown since 2006 over the course of listening to a wide array of equipment ranging from the low-end to the high-end that I have either owned, or been loaned, or have heard in quiet conditions at mini-meets.
I also believe in "Source First" as a listening methodology and that, in general, solid-state amps should not introduce their own sonic colorations into the signal path. I do, however, recognize that some solid-state amps are designed to have a sonic signature of their own, and in that case, I generally try to review an amp on its own sonic merit.
My Review Process (feel free to skip if not interested in reading)
The review process of any component that I review typically lasts at least 8 consecutive days. The first day I'll spend about 3-5 hours to form basic initial impressions. I'll then take the following 3-7 days (depending on timeframe allowed if a manufacturer loan) to listen actively and inactively. I'll then finish off my listening over 2-3 days to form final impressions and will also do intensive comparisons against other components during this period.
My writing process begins during the 3-7 day listening period when I start taking notes. I start writing after all listening has been completed and will take 1 day to translate all notes into a "beta" review - this usually takes 2-5 hours. The following day I'll read what I've written for content and major edits. After this editing is done, I'll check the review for syntax, sentence/idea structure, and format & flow. Once I'm satisfied, the review is considered done and saved into a personal archive.
Time spent for this XM5 review: 60-70 hours (due to product type I was able to listen to it at work on my laptop with 3 closed headphones and 1 IEM, in addition to at home).
Associated Equipment
Digital sources:
- Plinius CD-101 CDP w/ Signal Cable Silver Resolution Reference power cord, iAudio X5 (DAP), Asus Z71V (laptop PC)
RCA-mini Interconnect:
- Signal Cable SilverMini
Headphones:
- AKG K701 re-cabled w/ SAA Equinox
- Audio-Technica ATH-AD2000, ATH-ESW9, & ATH-ES7
- Denon AH-D2000
- Klipsch IMAGE
- Grado RS1
- Sennheiser HD650 re-cabled w/ SAA Equinox
Comparison USB DAC/amp:
- HeadRoom 2006 Total Bithead
Evaluation CDs
A Fine Frenzy - One Cell In The Sea
Alison Krauss & Union Station - So Long So Wrong, New Favorite
Kelly Sweet - We Are One
Laika - Good Looking Blues
Orbital - The Altogether (Disc 2)
Porcupine Tree - In Absentia
Renee Fleming - Thais
Sarah Brightman - The Andrew Lloyd Webber Collection
The Crystal Method - Community Service II
The Prodigy - Fat of the Land
Thievery Corporation - The Cosmic Game
Wynonna - The Other Side
About the XM5
The Practical Devices XM5 is the company's latest product in a line of headphone amp products that started several years ago with the original XMoy. The XM5 combines a headphone amp with a USB DAC for a true all-in-one DAC/amp unit. Its default op-amp is the TI OPA134, which is rollable to the AD8397 w/ DoubleCat. The buffers paired with this op-amp are the TI BUF634. Rail splitter is the TI TLE2426 in the virtual ground. Capacitors are high-value Electrolytic, Tantalum, and Ceramic. There are two colors available: silver w/ blue front panel, or all-black.
Technical specifications as listed on Practical Devices' Web site:
- Weight: 157 grams (5.5 oz) including alkaline battery
- Power Source: Lithium-Ion Rechargeable System, 9-volt Alkaline, or 9.6V Lithium Non-rechargeable
- External Power Supply: Optional Lithium-Ion Charger
- Battery Charge Time (approximate): Lithium FastCharge System: <1.5 hours
- Battery Life (approximate): Alkaline: 50 hours, Lithium-Ion: 40 hours, Lithium NON-rechargeable: 100 hours
- Maximum Gain: +20.6 dB (gain boost enabled), +12.7 dB (gain boost disabled)
- Frequency Response (20-20,000Hz, typical): +0.1dB, -0.4dB
- -3dB Point (typical): 21 kHz at top end; 9 Hz at low end
- Total Harmonic Distortion (typical): 0.0007%
- Intermodulation Distortion (typical): 0.005%
- Signal to Noise ratio (20-20,000Hz, typical): 103dB
- Dynamic Range (20-20,000Hz, typical): 103dB
- Bass Boost: +6dB @ 100Hz when enabled
- Treble Boost: +3dB @ 10kHz when enabled
- Crossfeed: Active, User-adjustable from mono to stereo using potentiometer; User can bypass using pushbutton
- Auto Power-OFF: user-selectable 1, 3, or 6 hour poweroff interval, or can be set to stay on indefinitely
- Status Indicators: two LEDS (one blue, one amber)
- Integrated Voltmeter accuracy (typical): ±100mV
- Mechanicals: Anodized aluminum case; Glossy laser-anodized faceplate; Polished aluminum volume knob; FR-4 dual-layer PCB with 1 oz. copper
- Other Features: Flashlight Mode: Turns on both LEDs to full brightness; Dimming mode: Allows user to optionally dim the blue LED; Fully configurable amplification and buffering using gold-plated sockets.
- USB DAC: 44.1/48kHz, USB 2.0 Compliant; Native compatibility with Windows XP, Vista; MAC OSX, OS9; most Linux installs
The XM5 ships with all accessories that you need to start using it immediately: an Allen hex key to open the amp, stick-on rubber feet, velcro stick-on dots, user manual, a 6" USB-mini cable, and an AC charger. At the time of this review, a 4.75" gold-plated mini-mini interconnect is also included at no extra cost when ordering new from Practical Devices.
Practical Devices recommended 8 hours of burn-in for the XM5 so I applied it before starting any listening.
Form & Function
As the latest product from Practical Devices, who's been making portable headphone amps for years now, the XM5 has a bit of a legacy to live up to. While I haven't heard the Practical Devices products prior to the XM4, I went into the XM5 with a small set of expectations, from a functional and operational point of view.
The basic physical design of Practical Devices products has remained consistent over their line so far, which is good - the XM5, like its predecessors, sits inside a basic Hammond enclosure fitted with a custom front panel. While a Hammond enclosure might be a bit of a retro throwback in 2008 (considering the recent spate of competitors using a variety of custom enclosures), it gets the job done. It might not look as aesthetically attractive as other competing products, but it's certainly not terrible looking, and you can rest assured it'll survive most physical situations.
In terms of operation, the XM5 is highly intuitive with clearly labeled buttons for Crossfeed, Bass Boost, Treble Boost, Gain Boost, and a 75 Ohm Resistance option. The push-button action is solid, and the buttons are spread far enough apart making it unlikely you'll accidentally press down two of them simultaneously. As for the input and headphone jacks, those are nicely spaced separately by themselves with no layout interruption, unlike the previous XM4 amp, which put the Bass and Treble buttons in a very inconvenient, interrupted layout that required pinpoint pushing due to their placement between the volume pot and the input/headphone jacks. Kudos to Practical Devices for revamping the layout into a form that makes much more sense and is easier to deal with.
The XM5's feature set goes past the already feature-packed XM4 to make it far and away the most feature-packed product in the portable USB DAC/amp market. As just mentioned, it has options for Crossfeed, Bass Boost, Treble Boost, Gain Boost, and 75 Ohm resistance. Of course, the XM5 is also a portable USB DAC which adds that functionality. And finally, like its XM4 predecessor, the XM5 contains a microprocessor that handles power management duties. The use of this microprocessor allows you to set the XM5 to turn on for 1 hour, 3 hours, 6 hours, or indefinitely (until the battery runs out). As this indicates, the XM5's battery powers everything and does not recharge over USB - only the included AC adapter recharges the battery.
Crossfeed, bass boost, treble boost, gain boost, and the 75 Ohm resistance all proved to be very useful options and most people who might choose to activate one or more of them should be pleased with the results. Yes, it's possible to activate all five buttons at the same time if you really want to, but of course that's not recommended. Not only does it shorten battery life, but I tried it - and the results weren't exactly ideal. Gain boost/75 Ohm resistance and bass/treble boost both effectively neutralize each other, making those two simultaneous options pointless.
If it weren't for the inclusion of the 75 Ohm resistance option, I would right now advise against using the XM5 with low-impedance headphones and IEMs. When this was disabled, the volume control over low-impedance headphones simply wasn't ideal and they got too loud too soon. When enabled, low-impedance headphones were much more easily controlled that it wasn't frustrating. Kudos to Practical Devices for adding this option in!
On the flip side, +8 dB gain boost proved to be only necessary for inefficient >300 Ohm headphones. With it disabled, the XM5 easily pushed the AKG K701 and Sennheiser HD650 to loud levels. In fact, there was still plenty of headroom left on the volume pot.
Bass and treble boosts did exactly what they're supposed to do. Treble sharpened up to near metallic and teeth-gnashing with its boost enabled, while bass got a very satisfying added thump in the approximate 50-80 Hz region. These options are of course best enabled on headphones that benefit from this sort of equalization. The bass boost worked well on the AKG K701 and Grado RS1 (with bowls), while the treble boost worked better on the Sennheiser HD650 and the Audio-Technica AD2000, ESW9, and ES7. However, it should be noted that the bass boost affects the mid-bass, and the treble boost affects the lower part of the upper treble. Neither added to their respective approximate extremity points - the treble boost clearly did not make upper treble more decimating in the 12-18 kHz range, and the bass boost clearly did not add any lower rumble or "buzz" in the audible 30-40 Hz region.
Crossfeed worked well enough to simulate a fair sense of soundstage on the Audio-Technica ESW9 and Grado RS1. As this is a very subjective area, I'll merely say that results will vary depending on the headphones being used, and that I really only recommend it on headphones that don't already throw much of a soundstage. The K701, for example, did not really benefit from it, as it seemed to collapse the K701's inherent soundstage. But it's still a useful feature and worth exploring depending on your headphones. And of course it's variable, so you can tune it to any amount that you want, all the way to a mono-channel setting.
Finally, the power settings proved to be very useful. While I didn't test this aspect with the previous XM4 in an amp-only setup in my StereoMojo review, this feature was a lot more useful with my laptop computer setup. Indeed, the power setting may very well be one of the most convenient features of the XM5 when used as a USB DAC, as it allows you to tune it in time to the battery life of your laptop computer or other USB source. The 3-hour and 6-hour settings allow it to be approximately matched up with almost any common battery life today. I did drain out the battery more than once though, so it didn't run all that long (less than 20 hours), but the XM5's low-battery LED lights up when it's almost depleted, making it unlikely that it'll be actually depleted in real-world usage (I ignored the LED and drained the battery on purpose). Although I neglected to time the low-battery LED, I would definitely say that it turns on within less than 1 hour of total depletion.
Listening Environments
I listened to the XM5 in three setups:
(1) As an amp lined out from the iAudio X5 DAP.
(2) As a DAC/amp connected to my Asus Z71V laptop computer, and compared to the HeadRoom 2006 Total Bithead.
(3) As an amp lined out from the Plinius CD-101 CD player (my main reference).
The listening from the iAudio X5 was brief. It did not provide any conclusive useful listening impressions. As iAudio X5 owners will know, this DAP tends to sound better directly from the headphone jack. I can only say that the XM5 worked well enough in this role.
In the laptop setup, files were in lossless FLAC, played back with Foobar2000 0.9.5.1, and output over ASIO4ALL V2. All software volume sliders were maxed out to avoid any software-based attenuation. Note: a software-based Loudness option showed up in the Windows KMixer when the XM5 was plugged in. This option repeatedly auto-enabled itself when the XM5 was plugged in at various times and I had to manually disable it.
In the Plinius CD-101 setup, the XM5 was directly compared against the HeadAmp AE-2 using the Signal Cable SilverMini RCA-mini interconnect.
All CD tracks referenced in the next section were directly A/B'd twice in both their Redbook CD and digital file formats for a comparison of the D/A conversion quality of the XM5's USB DAC versus the Burr-Brown PCM1704 DAC (plus analog output stage) in the Plinius CD-101. Using FLAC+ASIO on the laptop ensured a valid comparison of the DACs between the XM5 and CD-101.
XM5 vs itself - DAC vs amp
Due to its dual nature, a USB DAC/amp allows itself to be used as a total digital/anlog solution, or as just an amp only, so I compared the XM5 in this way - as the USB DAC/amp that it is, and in amp-only form off my Plinius CD-101. This comparison can also be seen as putting the XM5's USB DAC up against the Plinius CD-101's PCM1704 (plus analog output stage) as the constant being kept here is the amp section of the XM5, which is why I refer to "XM5 DAC" and "Plinius DAC" below.
In short, there was no contest here. The XM5 sounded way better in every way in amp-only form with my Plinius CD player than it did as a USB DAC/amp, showing that its USB DAC limits its performance in that mode.
On Kelly Sweet's "Ready for Love" from her CD We Are One, the background details were more prominent with the Plinius DAC, most notably the piano, as there was greater presence to it. The Plinius DAC also sounded more graceful and fluid, whereas the XM5 DAC sounded like it was being "directed" about by an unnatural force. On this track, Kelly's voice was also firmly positioned and planted on the Plinius DAC, while there was an odd modulation type effect on the XM5 DAC - her voice seemed as if it was moving back and forth from slightly left to slightly right in the soundstage. This was highly noticeable on the K701 and even moreso on the AD2000. In addition, Kelly's voice was more direct and upfront on the Plinius DAC, while it was slightly recessed on the XM5 DAC. On another track on this disc, "Dream On", the Plinius DAC was simply richer-sounding, as it sweltered with much more musical information, most of which contributes to the heart & ambience of this track. The Plinius DAC also sounded more diffuse and less concentrated than the XM5 DAC, with a clearer picture of the individual musical elements "suspended" in the sonic image. The XM5 DAC, on the other hand, provided much more of a concentrated, "dissolved" image where the musical elements did not sound clear and discrete.
On Alison Krauss & Union Station's "It Doesn't Matter" from So Long So Wrong, the XM5 DAC was noticeably slow and didn't really get the fast movement squeaks and string taps on the opening notes. On good equipment, you can hear various physical movements (including something squeaky) on the opening 30 seconds or so, along with a clear tapping on the strings that one band member is doing to his instrument, but this barely came across on the XM5 DAC. The Plinius DAC was also very airy, open, and expansive on this track, almost as if the venue were an auditorium, while the XM5 DAC caught much less venue air that it sounded more like a studio. The notes from the double-bass were not very strong and deep on the XM5 DAC either and didn't leave an impression of being anchored very well. The Plinius was also more dynamic, as it effortlessly caught the modulating volume levels of both Alison's vocals and the soft-to-moderate levels of the band as they surround her voice. The XM5 DAC had a tendency to make the volume of each musical component more equal relative to each other, and it did not reveal the softly-rolling dynamic contrasts that the band provides throughout the track.
The XM5 DAC continued to underwhelm with two more AKUS selections, "The Lucky One" and "Take Me For Longing" from New Favorite. The Plinius DAC simply sounded more like music. "The Lucky One" was full and expressive, with plenty of detail on all counts. There was lushness to Alison's voice, along with air around it too. The bass rhythm was deep and anchored, and there was a huge step forward in the transients with the Plinius DAC - the XM5 DAC was simply too soft and dull-sounding. "Take Me For Longing" gave an even better picture of the contrast, as the XM5 DAC made the band sound more like they were half-dead or asleep. The Plinius DAC was a huge step above, as the band just swung around way more and sounded alive rather than half-dead. The comparison was nearly night versus day - on the Plinius DAC, the banjo had way more energy and groove (and a metallic sheen too), Alison's voice was forward and prominent, and there was bite and snarl. There was also a big expansion in the ambient space for increased spatials.
DAC Mode - XM5 vs Bithead
This was a relatively short listening comparison. The two USB DAC/amps were on mostly equivalent footing for the most part, though the XM5 did come away with the upper hand. This was my first time listening to the Bithead with FLAC over ASIO (until this review I'd only heard it in MP3 over Windows KMixer), and it sounded very good actually. The mid-range was nicely full and warm, with good solid bass performance, decent soundstage width, and no serious lack of detail.
The XM5 also gave a nice and full mid-range, about on level with the Bithead. Bass, however, was not entirely fully anchored on the XM5, as it tended to lose control on very deep, loud bass notes at higher volumes. The louder the bass notes the more it tended to lose control, as they got slightly wobbly. Granted, this only really showed up at high volume (but not excessively high, merely loud), and at anything less than high volume it was perfectly fine - good, deep, controlled bass. The Bithead, on the other hand, had a better anchor on the bass at high volume, except it tended to get excessively boomy. So there was a definite trade-off between the two - boomy bass on the Bithead, or uncontrolled, wobbly bass on the XM5, and again, only at high volume.
With none of the buttons activated, the XM5 ended up sounding pretty similar to the Bithead otherwise. In other words, neither was really a stellar performer as a USB DAC/amp, though the XM5 did do slightly better in some areas. It was slightly more detailed for one, and soundstage was slightly wider. But the main advantage of the XM5 was a fuller, more expressive mid-range that made it sound "sweeter," whereas the Bithead failed to draw in much emotion. A somewhat more musical sound, essentially. And of course, the XM5's sound can be tweaked through the Bass and Treble Boost buttons, which propel it above the Bithead which has only crossfeed.
However, as described in the section above, the XM5 opened up way more as an amp over its USB DAC/amp combined sound.
Amp Mode - XM5 vs AE-2
The amp section of the XM5 was compared to the HeadAmp AE-2 on the Plinius CD-101 using the Signal Cable SilverMini as interconnect.
On Porcupine Tree's "Wedding Nails" from In Absentia, and with the Grado RS1 headphones, the XM5 and AE-2 traded roughly equivalent blows. The XM5 was the less bright and less metallic-sounding amp, and it provided a more realistically small soundstage as well, as the band sounded closer for a more intimate presentation. There was also more mid-range meat on this track with the XM5 that fleshed out the various layers, including the guitars. However, the AE-2 had the upper hand on more aspects - it displayed faster attack and caught more transient information, allowing it to give proper bite and crunch on the dual guitars for example. Also, while the XM5 did make the guitars sound less metallic, the AE-2's portrayal was more detailed, as the metallic sound seemed to be part of their texture. The AE-2 also had more energy and better separation of layers, making it easier to hear the individual instruments. It was also more open-sounding and did not limit the band to sounding like they were stuffed up, as the XM5 did.
On Wynonna's "Troubled Heart and a Troubled Mind" and "The Wyld Unknown" from The Other Side, again with the Grado RS1, the XM5 balanced out the RS1's signature more than the AE-2. It gave more mid-range swarth overall, and drew out the backing instruments to sound full, heavy, and long, with plenty of presence and weight. The AE-2 sounded downright disembodied in comparison. The soundstage with the XM5 was also small and intimate for a good realistic portrayal. The AE-2, on the other hand, while not as nicely complementary with the RS1, was superior to the XM5 most noticeably in the areas of PRAT and treble. It was more light-footed and energetic, and conveyed the up-tempo insistence of both tracks far better, as it was just that much more quick and toe-tapping. The AE-2 also gave proper snarl to the guitars and overall simply sounded more "electric." The lively spark of both tracks came fully across on the AE-2, whereas the XM5 lost much of it.
Renée Fleming's recording of Thais, in "Je n'ai pas plus choisi mon sort que ma nature!" from Act 2 Scene 1, is well-recorded and contains one of the greatest operatic dialogues in Romantic-era classical. It takes some serious equipment to get this track right, and neither the XM5 or the AE-2 did. The AE-2 got closer though, as the XM5 didn't punctuate Renée's dramatic vocal bursts nearly as much (and the AE-2 itself didn't do that much punctuation either, at least in comparison to other amps I've heard), and it lost some control over her voice too, taking away some of her vocal power. The XM5 was not as quick on the cymbals as the AE-2 either, just missing the initial stick-impact and tizz, for an incomplete portrayal. And it did not hold the rolling lyrical passages as well as the AE-2 either. The AE-2 did itself struggle to hold onto the dynamically-shifting lyrics, but the XM5 just couldn't seem to stay with the dynamic contrast, and as a result the lyrics didn't roll or swell on it.
Sarah Brightman's version of "All I Ask Of You" from The Andrew Lloyd Webber Collection went better for the XM5 than Thais did. The XM5 had a bolder, slightly richer, more harmonic tonality, that fleshed out the orchestra and two vocal parts nicely. There was no major loss in detail with it either. True to the AE-2's nature though, the vocal parts emerged from deeper in the soundstage on that amp, and the orchestra sounded more sweeping on it thanks to greater air span. The violins were also more separately delineated with the AE-2, and sounded more like a collection of multiple violins with it, where they were more converged on the XM5.
The title track from Alison Krauss & Union Station's So Long So Wrong is one of my standard acoustic references for listening to overall frequency balance and soundstage positioning, along with female vocal portrayal. The XM5 recovered a bit here, with a good strong and prominently bowed-out presentation. Bass was rich and deep on it, and the mid-range was very noticeably filled out compared to the relatively thin-sounding AE-2. Lots of "meat on the bone" so to speak, and it was very nice-sounding overall. Instruments were positioned closely for a realistic venue feel, and even more with Alison's voice, for a somewhat "personal" presentation on her voice. The AE-2 took the upper hand here most noticeably with a more ethereal quality to Alison's voice, faster transient response on the banjo, and higher-quality, textured bass. The XM5's bass did have more quantity though.
Laika's "Widows' Weed" from Good Looking Blues is one of my standard electronica references for testing clarity, detail retrieval, and soundstage precision. The XM5 for the most part fell flat on this track, compared to the AE-2. The bass line, which isn't even all that deep, was fuzzy and indistinct on the XM5. It didn't have the snap-to-grid focus of the AE-2 either, as the various working layers were blurry and unclear. The moving layers that are supposed to drift fluidly between channels, did not on the XM5. There was no sense of ease and fluidity on it. Notes did not appear from a truly black background on it either - there was a slight sense of a gray background with it, as there was no ear-popping vibrancy. Treble wasn't quite as clean and fast as the AE-2's, and to top things off, the XM5's small concentrated soundstage seemed like a large-scale detraction from the AE-2, which was much more diffuse and dispersed. The AE-2 conveyed much more free-roaming air and space that is evident on this track, and it had the greater soundstage width too, with further displacement of left from right.
Thievery Corporation's "Holographic Universe" from The Cosmic Game was next on the plate for a brief test of bass definition, but the XM5 paled next to the AE-2 here. The insistent, driving bass rhythm was not distinct on it and was nearly one-note in pitch. There was not much tone to it either, it was very generic-sounding.
For a true bass test though, The Prodigy's "Smack my B**** Up" from The Fat of the Land is more like it, and it's here where the XM5 finally ended up delivering more than the AE-2, mainly in the area of quantity. It gave a plentiful, satisfying, focused boom and thump, with more force and more power. A harder overall impact. The XM5 did add its satisfying mid-bass to the AD2000 too, which made this track that much more bass-heavy. However, the XM5's lack of speed was highly noticeable on this headphone, and the various elements that should pop, mostly didn't. In addition, the XM5 did not match the Audio-Technica AD2000's bass extension to provide much in the way of low rumble and visceral force. "Fuel My Fire", the last track on this disc, opens up with an active, deep, and low-firing layer, most of which was lost on the XM5. It just couldn't serve up this low bass with much power and instead tipped the scale with more mid-bass output than low-bass.
In a final test, Orbital's "Bigpipe Style" from The Altogether (Disc 2) completed the picture of the XM5's bass quality. Compared to the AE-2, the XM5 had the more massive-sounding bass and threw around more punching-ball force, along with a more down-and-dirty attitude. The AE-2 was leaner yet more controlled and refined, and gave more bass texture.
vs the HeadAmp Pico?
It's probably the question many have on their minds - can the XM5 hang with the HeadAmp Pico? While I can't conclusively answer this due to not having heard them at the same time (I sold my Pico before I received the XM5 review sample), I did extensively listen to the Pico for more than 60 hours just before I went into the XM5.
My short answer is that the HeadAmp Pico is the clearly better sounding product, but you'll pay more than twice the amount of the XM5 to get one. The Pico also has a much smaller feature set (really, almost none, save for the two-way gain switch). It's up to you to decide if you want to spend $500 for a better-sounding USB DAC/amp but with fewer features (not to mention the Pico's highly fingerprint-prone chassis as well).
Conclusion
The Practical Devices XM5 is a decent value at $235 for a USB DAC/amp, but I found it limited by its USB DAC, as it opened up much more as just an amp. It's still a definite upgrade over onboard laptop sound, somewhat on level with HeadRoom's 2006 Total Bithead, so it's perfectly acceptable-sounding and it may be a good solution for the mainstream of budget-fi rigs. The main detraction I found with it was a range of sonic omissions when used as a USB DAC. It's a fine product for non-demanding listeners but I would recommend that serious, critical listeners with revealing headphones look elsewhere.
Practical Devices has certainly done a fine job in the XM5, and in most ways it is a step above the previous XM4. I did not get to evaluate it with a supplied Analog Devices AD8397, though I would've liked to do so. I suspect the AD8397 would take the XM5 even further as an amp.
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