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FIRST LOOK: HIFIMAN HM-901 HIGH-RESOLUTION DIGITAL MUSIC PLAYER/DAC What follows is a “First Look” blog about a very special high-performance digital audio player that has, if truth be told, gone through one of the longest gestation periods in personal audio history. The product I am spe


What follows is a “First Look” blog about a very special high-performance digital audio player that has, if truth be told, gone through one of the longest gestation periods in personal audio history. The product I am speaking of is HiFiMAN’s HM-901 high-resolution digital audio player/DAC, which began its journey toward the marketplace roughly three years ago.

The HM-901's design pays homage to both the Sony Walkman and Apple's ubiquitous iPods

Honestly, three years doesn’t sound all that long, but as gauged in digital product development cycles it’s an eternity. To appreciate how far ahead of its time the HM-901 was it helps to flip our imaginary high-end audio calendar back to 2011. Back then the following conditions prevailed:

  • Computer audio was gaining momentum like crazy, but there were still many reservations about using USB interfaces as the preferred vehicles for feeding digital audio files to DACs. At the time, S/PDIF was considered the safer, more reliable, and higher performance interface of choice.
  • Personal digital audio players were considered useful devices—perhaps especially so as storage devices—but no one really expected them to have serious, high-quality digital and analogue circuitry on board.

  • 96/24 files were considered “high-resolution” files and 192/24 files were regarded as “ultra high-resolution” files. Today’s whole DXD/DSD craze hadn’t even begun yet.

  • While personal digital audio players with solid-state memory had begun to gain traction (thanks to the ever-evolving iPod Touch), not an awful lot had been done with use of SD cards as storage for audio files.

  • The working assumption was that genuinely high quality, high-performance DACs and headphone amplifiers would be desktop—not portable—units.

  • Astell & Kern had not yet become a significant blip on the high-end personal audio radar screen.

HM-901 arrives in this presentation case

Against that backdrop, the working design brief for the HiFiMAN HM-901 began to unfold, emphasizing the following key features:

  • The HM-901 would be a portable, high-resolution, 192/24-capable DAC, digital music player, and headphone amplifier.

  • Handling digital-to-analogue tasks would be not one but two very high performance ESS ES9018 Reference Sabre32 8-channel DAC devices, with each device used to process just one audio channel.

  • The HM-901 would have a coaxial S/PDIF DAC input. It would also have USB connectivity, though USB would be used only for downloading digital audio files to the HM-901s onboard memory card.

  • Unlike many then-current portable players, the HM-901 did not have a fixed memory size. Instead, it used camera-style SDHC memory cards, giving the HM-901 Storage capacity of up to 128 GB.

  • The HM-901 was designed to support many different file formats (WAV, FLAC, ALAC [M4A], AIFF, AAC and APE) and could, depending on file format chosen handle PCM files from 44.1/16 on up to 192/24. Remember, the whole DXD/DSD movement had not started yet.

  • The HM-901 aimed to have an elaborate, full-colour, Apple-influenced graphical user interface that would feel instantly familiar to a generation of iPod users.

  • The HM-901 was planned, from the outset, to accommodate a variety of interchangeable, special-purpose amplifier modules, allowing the player to be tailored for use in a wide range of application scenarios. In particular, HiFiMAN made sure there would be a very low-noise amp module for use with super-sensitive in-ear monitors, but also a full on balanced output amp module for use with more power hungry ‘phones.

  • Finally, in the original plan, the HM-901 was to have been available with an optional, tabletop DAC docking station that would allow the HM-901 to serve as one’s primary DAC in a high-end audio system, yet would allow the HM-901 to be undocked for on-the-go listening.

HM-901 with all of its included accessories

Looking back, it is easy to see that, if the HM-901 had come out when initially expected, it would have been regarded as an engineering marvel, but unfortunately for HiFiMAN that isn’t quite what happened. 2012 came and went, as did a significant chunk of 2013, all without the final, fully debugged, production-version HM-901 putting in an appearance. Meanwhile, we all saw the release of the groundbreaking Astell & Kern AK100, followed by the now-iconic AK120, and later still a preview of the soon-to-arrive AK240. Even so, the concept for the HM-901 was so far ahead of its time that the finished product for the most part can hold its own with (or perhaps in some respects even surpass) the more recently released Astell & Kern players.

HM-901, left side, showing SDXC card bay hatch cover

What took HiFiMAN so long? I can’t say for sure, but a significant piece had to be the sheer ambitiousness and complexity of the original design brief. There was, too, the age-old problem of achieving consistency of production and, more importantly, glitch-free software/firmware performance with what is an inherently complex, multi-function product. In any event the HM-901 (which ranges in price from $999 to $1,279 in the US, depending upon the amplifier module chosen) is here now and performing smoothly at last. Was it worth the wait? I think it was and is, though like many of you I can’t help but think what sort of impact the product might have had if it had come out a year and half earlier…

HM-901, right side

The HM-901 can be ordered with any of four (count ‘em) different amplifier modules: a standard module ($999), an IEM module ($1,199), a Minibox module ($1,199), or a Balanced module ($1,279). Our review sample came with both the Standard module and the Balanced module, so that we could try the HM-901 with both its entry-level amp and with its most powerful amp (suitable for many though not all full-size headphones).

HM-901 top view showing headphone jack, which supports both 3-conductor and 4-conductor (TRRS) mini-plugs

HiFiMAN’s HM-901 arrives in a padded presentation case along with an included battery charger, a USB cable, and an S/PDIF input/stereo line out cable, plus an Owner’s Guide. The long-awaited DAC docking station has yet to be released.

We probably ought to discuss the HM-901’s industrial design, which could best be described as “vintage Walkman neo-funky.” In other words, this baby looks like a 21st century take on the styling of a vintage Sony Walkman. This makes perfect sense when you consider that HiFiMAN got its start by rebuilding and then hot-rodding defunct Sony Walkman products to turn them into—you guessed it—HiFiMAN players. If you love the sleek, ultra-moderne look of the Astell & Kern players (and I do), you might at first find the HM-901 a little clunky and anachronistic. However, if you love a good bit of techno-homage in celebration of glories past and yet to come (think VW’s New Beetle or the new Mini Cooper S), then the HM-901 may well put a smile on your face.

How does it sound? Thus far I’ve spent most of my time listening to the Standard amp module driving my Westone ES-5 and Ultimate Ears Personal Reference Monitor custom-fit IEMs and you can colour me impressed. This might be one of the nicest, clearest, most articulate (yet still robust-sounding) DAC/amp/players I’ve tried thus far with my top-shelf IEMs. If the HM-901 sounds this good with the Standard Amp Card, just imaging how good it might be with the dedicated IEM Amp Card. At the moment, I’m temporarily on hold in terms of listening to the Balanced amp module as I’m going to need an adapter or two to give it a proper evaluation. If it turns out to surpass the Standard Amp Card (and I fully expect it will do just that), we’ll all have cause for rejoicing.

The HM-901 Amplifier Card bay is tucked beneath the battery (shown here with battery removed)

The HM-901 (with the latest and greatest HiFiMAN firmware revision) has been able to switch cleanly between the 44.1/16, 96/24, and 192/24 files I have loaded on my SD card. This is all to the good. Might HiFiMAN eventually add DXD/DSD capabilities? Only time will tell. Nevertheless, high-res PCM can be a beautiful thing in its own right (despite the buzz that DXD/DSD files have generated), whose benefits the HM-901 is only too happy to reveal.

Alternate view of HM-901 Amplifer Card bay

My only gripe, thus far, is that the Owner’s Guide is a little bit out of sync with the actual characteristics of the HM-901 as presently delivered (not a big deal, because the user interface is so intuitive, but definitely the sort of thing that might keep detail-minded, OCD sufferers awake nights trying to work out the discrepancies).

HM-901 Amplifier Cards swing out for easy access

Even so, the HM-901 has become one of my favourite vehicles for listening through top-drawer custom-fit IEMs. It looks cool, sounds waaay cool (even with just the entry-level Standard amp module installed), and is big fun to use.

HM-901 Standard Amplifier Card (left) and Balanced Amplifier Card (right)

One quick follow-on thought: If you like the concept of the HM-901 but find it a little too pricey for your budget, you might want to know that HiFiMAN now offers an alternative, lower-priced (but not features reduced) version of the player called the HM-802, which achieves cost-savings by substituting a Wolfson WM8740 Dual DAC in place of the HM-901’s very costly twin ESS ES9018 DAC setup. What kinds of price reductions are we talking about? The HM-802 starts at $699 for the Standard Amp Card version and ranges up to $979 for the Balanced Amp Card version.

Watch for an upcoming Hi-Fi+ review of the HM-901 and until then, happy listening.

2014-03-12 21:24:47
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