HiFiMAN HM-802
Most headphone aficionados these days know HiFiMAN for their planar magnetic full size headphones. That seems to be the main focus now, along with a supporting cast of desktop amplifiers. But veterans in the headphone game probably still think of the firm as an IEM company, as that was their main focus in the years before the planar magnetic revolution. HiFiMAN was also one of the few companies making expensive DAPs, until this new wave came along. Their HM-801 was popular in 2010 when practically zero competition existed in the premium category.

While not exactly receiving the same attention as the planar magnetic headphones, HiFiMAN's DAP line has steadily evolved over the past few years. This culminated in the $999 HM-901 which remains the current top model (until the upcoming 901S officially launches in the USA). That thing has been reviewed many times over the past few years so I chose to cover its little brother, the more recently released HM-802 ($699). The 802 received very little attention for some reason, despite being a very similar product in almost every way...for a lot less money. After comparing the two directly, I may actually prefer the cheaper sibling, so it's definitely not something to overlook merely for being in "second place".

External Design
The HM-802, at first glance, looks like it might be a Tascam field recorder. You know those sleek lines from the AK240? The modern look of the Calyx? You won't find any of that here. The HM-802 is unapologetically bulky. It's got an old-school vibe to it, but not in a hip, retro way. Build is mainly plastic and feels a little cheap at times—the battery cover is especially obvious. But the boxy look and 250 gram weight (the heaviest in this comparison) somehow counteract the plastic feel by making the device seem virtually indestructible.

As you can see in the pictures, the 802 has a rather busy design. We get a grand total of 6 switches, 6 buttons, and two spinning things with which to control various aspects of the player. That maybe sounds more complex than it really is, but let's be clear—this thing doesn't possess even a fraction of the grace found in the Astell&Kern models.

Size comparison between the HM-802 (bottom) and Calix M (top).

Internal Design
The HM-802 is essentially the same as HiFiMAN's HM-901 but with dual mono Wolfson WM8740 DACs used in place of the 901's dual ESS chips. They also redid the output stage, optimizing for the unique requirements of the different chips. Everything else remains, same stepped-attenuator based analog volume control, same gain options, same battery, etc. The "Wolfson sound" is stereotypically thought of as being warmish while the "Sabre sound" is more lit up. I don't put much stock in these universal generalizations though at times they do happen to line up with reality.

By far the most interesting aspect of the device is its modular nature. Remove the battery and you'll see the amplifier "card" which can easily be swapped out for another. HiFiMAN has several different cards available which focus on different things: one for balanced mode, one dedicated to IEMs, etc. This means the device can be tailored to a particular need more so than other DAPs which lack this modular design. It's worth noting that more amp options exist in HiFiMAN's home market—I've even seen some hobbyists design their own cards. The choices available for us in the USA are somewhat more limited, though an enterprising 802 user could eventually track down more cards if they really worked at it.

The 802 supports hi-res PCM up to 24-bit/192kHz. It supposedly handles DSD, limited to DSD64 in the DFF format. I was successfully able to play DSD tracks using an older firmware, but when I updated to the latest it no longer works—I mainly hear static. I also get static playing 24-bit/176.4kHz material. To be fair, that (rather uncommon) sample rate has caused issues in the past with other gear.

User Interface
HiFiMAN calls their UI "Tai Chi", ostensibly meant to suggest smooth, flowing operation. I see what they were going for but frankly I don't think it worked quite as well as they intended. The UI is serviceable but nothing more. With the exception of Fiio's X5, every other DAP here has an edge over the 802.

A large portion of my complaint is actually centered around the scroll wheel, which is just not very responsive. As with the X5, it seems like a solution waiting for a problem. A simple 4-way button system would seem a better choice. If they were dead-set on keeping the wheel for some reason, it would need a better feel to it—both the surface of the wheel and the way it acts in the menu. As it stands I end up spinning the wheel and never being confident I'll see a corresponding action on the menu. The wheel is physically slippery despite having several "ribs" for grip. And it seems too stiff—I thought it might break in a bit after use, but so far no change.

Aside from that, the UI is attractive enough if fairly basic. HiFiMAN has a demo available hereallowing you to see navigation and playback. As you can see, it's a fairly straight forward UI that gets a slight boost from little animations and such—but it's still nothing too amazing.

Connectivity
HiFiMAN made some interesting choices here. On the plus side, we get a full size SD card slot, which means higher capacity cards for lower prices than their microSD counterparts. This is welcome since the device has no built-in memory of its own. We also get the option of balanced output when using HiFiMAN's balanced amp card—it uses a 3.5mm combo jack which also works with standard unbalanced headphones. This is different from the A&K DAPs which use a separate 2.5mm jack for balanced mode. Lastly, a bundled adapter provides analog RCA outputs and a digital (SPDIF) input connection, for using the 802 as an outboard DAC.

On the flip side, there are some negatives here, chief among them being HiFiMAN's choice of a proprietary connection jack. This means dedicated cables are required for charging, data transfer, and anything else that might interface with the device. Since most others use standardized microUSB, this is a minor annoyance. Also note a complete lack of any wireless connectivity—which may or may not matter to you.

HiFiMAN does have a noteworthy accessory called the Dock-1. It's a substantial desktop dock which costs $499 and adds significant functionality. This device has made appearances at shows going back several years, and is one of the reasons I wanted to try out the 901 when it first came out. It finally became available and, while expensive, looks like a very useful device. It boosts the line output level to as much as 3 Vrms, adds a host of inputs and outputs, adds a remote control.... this effectively turns your DAP into a legit source for desktop use. Oh, and it looks great in the process. If this sort of thing is to your taste, it could really set the HiFiMAN units apart from their competitors.

Battery
The HM-802 lasts roughly 10 hours which is midpack in this roundup—it's not amazing, nor is it terrible. It seems to be fairly consistent in that playing high-res tracks or driving more power-hungry cans doesn't drain the battery much more quickly, compared to playing CD quality tracks via IEMs. Other DAPs show more variation in that regard.

Sound Quality
The HM-802 is a very enjoyable player. All my gripes about the controls and the UI seem to fade once I hear the lush, velvety presentation. It's not terribly dissimilar from the Calyx M in some ways—both have somewhat relaxed top ends which don't seem to suffer a lack of detail, but rather present things in an effortless, fatigue free manner. Where they differ is that the 802 is even more relaxed, even warmer, with a sweetness of note that screams "analog" even more loudly—for better or worse. If the Calyx is a classic Parasound DAC (to follow the analogy I used prior), the HM-802 brings to mind the Audio Note DACs and CD players. Those models (not cheap!) used older DAC chips such as the Philips TDA1543, the Analog Devices AD1865, or the TI PCM63, and are known for their rich tonality.

The resulting sound is something I usually find compelling, though I can see how it might not be appealing for others. It doesn't have the sparkle some people love, and when paired with a darker headphone the sound is a bit muffled and closed in. Those seeking a more neutral, linear presentation should look elsewhere—perhaps consider the HM-901 which sounds more lit up and resolving but to my ears less musically pleasing, again depending on the situation.

Of course, that warm tone of the 802 is just a baseline, and the final result will be determined by your chosen amp card. $699 gets you the standard amp module based around an Analog Devices AD8397 opamp. With a 1 ohm output impedance and a max output of 150mW in high gain mode, the standard card is a good all around performer. It can sound a little constricted at times, and tends to lose the plot with complex material, but aside from that I'm pleased with its performance.

HiFiMAN also sent along an IEM card and a balanced card, both of which improve performance even further. The IEM card ($229) uses a pair of OPA627 opamps each driving an OPA634 buffer. Output impedance is 2 ohms which is acceptable for all but a few IEMs. The low gain setting tops out at 1v and 33mW which might sound inadequate for big headphones but is perfect for IEMs. The resulting noise floor is exceedingly low. High gain mode delivers 1.4v and 65mW making it suitable for more than just IEMs, but it still can't handle tough loads. The sound signature of the IEM card is a bit more neutral than the stock amp—it's got superior resolution and doesn't sound muffled as the stock card sometimes can. It also does a lot better with orchestral works and other complex material. To my ears, the 802 with IEM card is up there with the Calyx M and AK240—but only when listening with IEMs or other easy to drive cans.

The balanced card ($299) is very similar to the IEM card but doubles everything—so quad opamps and buffers. It's basically two of the IEM cards combined onto a single PCB. In low gain mode, using a standard unbalanced headphone, the output is nearly identical to the IEM card—which makes sense, as it only uses "half" of the amp in that configuration. Using a headphone terminated with a balanced TRRS plug, flip the switch to balanced mode and enjoy the full potential of this amp card. Balanced mode on the high gain setting pushes a very impressive 477mW and swings nearly 4 volts, making it potent enough to drive most full sized cans with authority. It's characteristics are very similar to the IEM card—top end clarity is significantly improved over the stock amp card, and soundstage is quite a bit more expansive and layered. The only downside? The TRRS termination is not all that common. HiFiMAN's RE600 IEMs use it, and those sound great using the low gain setting, but all that extra power isn't really necessary. Aside from that IEM you'll need adapters to make the most of other balanced headphones. If you need the power though, the balanced card may be just the ticket.

Conclusions

The HM-802 is a generally solid DAP. The UI is a bit clunky and it isn't the most feature packed device out there. The modular design is very clever though—I really enjoy the amp cards I've tried, and there are several other well regarded options which I didn't get to play with yet. That makes the 802 almost more of a "platform" than a mere DAP. The sound signature certainly isn't for everyone, but for those wanting a rich, full bodied sound, this could be the perfect fit.

HiFiMAN HM-802 product page and HeadFi discussion thread.