Hifiman HM-801
Disclaimer: This review is just a reflection of my opinions and experience.

Specifications:
- Modular Design: Modular Amplifier Bay (Named GanQi Bay) and 14.8 volt Lithium Polymer Battery Bay
- Memory: SDHC Card
- DAC function: Coaxial (44.1kHz, 96 kHz) , USB DAC (16bit, 48kHz)
- DAC Chip: Burr-Brown PCM1704U-K (for Player, Coaxial and USB) ; Op-Amp: OPA627
- Size: 114 mm *78mm * 25.5 mm or 4.49 * 3.07 * 1.00 Inch
- Output: Headphone out; Line out
- Exchangeable Module Battery Life : 7 to 8 hours (Depending upon which Modular Amplifier board is mounted)
Contents in Packaging:
- HM-801 Player
- 110v AC to 18v 2000mA charger
- USB cable
- Coaxial cable
- Philips screwdriver
- Microfiber cloth
- Carrying pouch


User Interface:
The Hifiman HM-801 has a very basic and straight to the point UI. With a very small color LCD display and 5 circular buttons located beside it, immediately you get the idea that this player isn't about modern day bells and whistles typically found in the latest Cowon player or Apple iPod Touch. The HM-801 also has 4 buttons at the top of the unit. The 4 buttons are the power button, skip back or reverse button, skip forward or fast forward button and the play and pause button for quick and easy accessibility to your music without having to look at the screen. Alongside the screen, are the "at first" awkwardly presented 5 buttons that are responsible for navigating through the HM-801's UI. The top 2 buttons are the back and forward buttons. They allow you to leave a menu screen or advance further into the menu. The single button in the menu is your "select" button. This button confirms a selection. The bottom 2 buttons are the up and down buttons which navigates the selector up or down. Like I said before, at first they're a bit awkward, but after awhile they become second nature and you will fly through the UI. The UI isn't without flaws though. There isn't a "search" option and the overall response time of the buttons and the menu is sluggish. There are several bugs such as the device sometimes freezing to the point where the battery needs to be completely removed and placed back in. You select a song and a completely different song begins to play. You're scrolling down the list of your songs and the device begins to play a song randomly. These are very small problems that don't hinder the ability to use the device, but they're still problems that I hope get fixed down the road.
Adding music to the HM-801 is very simple. Either plug the SDHC card directly into your computer and copy the music files over or plug the HM-801 up to your computer via a USB cable and also have access to the built in 2gb's of storage for upgrading the firmware or music storage. The HM-801 also acts as a USB or Coaxial based DAC. Personally, I found the sound quality to slightly suffer when doing this ( haven't tried coaxial), but it still outperforms the sound quality out of my laptop's 3.5mm headphone out. Surprisingly, there is a 5 band equalizer in the HM-801's UI though it has done more harm than good in my opinion.
The UI for the HM-801 can be upgraded to the Rockbox firmware which allows the HM-801 to finally have gapless support as well as a bunch of new features. As of now, the Rockbox firmware for the HM-801 is in a very un-stable form and the support to improve it's stability doesn't seem to be growing unfortunately...
Build Quality:
Despite being manufactured by a small company in China, the build quality is very good. It's not as good as say something as mass produced as an iPod, but it doesn't look like it will fall apart on it's own over time. Even though it's essentially a "brick", it's a sleek looking brick in my opinion. The shiny back metal with the gold accents really give it a serious look. If you've grown up using Walkmans, you'll grow to appreciate the HM-801 aesthetically even more. The main gripes that I have with the HM-801 in terms of the build is that it's both a finger print and scratch magnet thanks to the type of material used for the exterior. The scratches aren't easily noticeable in normal lighting, but when you take it under intense light such as outside, the scratches really begin to show themselves and annoy you. Also, the gold paint on buttons will wear off over time.


Battery Life:
With such power hungry components jammed into this thing such as the PCM1074UK and OPA627 chips, the battery must be able to deliver a lot of voltage and current. The HM-801's battery life is rated at around 7-8 hours. I get roughly the same times too. This player needs to be strapped down by it's charger every night if you're planning to frequently use it during the day. Purchasing another battery can extend the potential time you have with the HM-801 to 14-16 hours. Also, I wanted to note, the HM-801 itself warms up during music playback and warms up a bit further during charging. The AC charger also gets warm too which is expected of any charger giving out so much power in DC. The HM-801 will not charge via a USB cable simply because of the low power output, but surprisingly, the menu can still be navigated with only power from a USB cable. No music will play from a USB cable though.


Sound Quality:
With everything else aside, we approach the most important aspect of the player, the sound quality. The only thing I've used to listen to this player was my Westone ES5's. The amplifier module inside this unit is the Standard v2 amp. I did not use any external portable or desktop amplifiers with the HM-801 during this review. The majority of my music is FLAC with about 30% of it being 256-320kbps MP3. The portable mp3 player I will be comparing the HM-801 to is the iPod Touch 3G.
The HM-801 has a warm, euphoric and spacious sound. To those who prefer a more accurate and linear presentation, this player may not be your cup of tea. Compared to my iPod, the iPod has more lively and energetic sound mainly due to the lack of lower and upper treble roll off. This is just frequency response alone. As we step out away from that and approach detail retrieval capabilities, texturing, soundstage and realism, the iPod simply cannot hold a candle. The iPod sounds hazy, muddy, cold and lifeless compared to the HM-801. I never thought muddy and cold could be associated with each other when describing sound, but the iPod changed my assumptions.
Bass:
The HM-801's bass is very bold and powerful. Not, overly so, but enough to add a nice foundation to your music. I can much more easily hear different bass notes as they simultaneously play. The bass extension far exceeds my iPod which made me think my Westone ES5's just didn't have the extension capabilities I expected. Plugged into the HM-801, my Westone ES5's pumps out bass that I would seriously expect from a full size dynamic driver headphone. With such a present and authoritative bass, the rest of the music is surprisingly left unharmed. The bass not only hits harder, but with a more sharper and tighter focus behind every hit. This is a result of the higher power output that the HM-801 can easily supply. The iPod's bass punch isn't terribly bloated or boomy, but it's just not as vivid and focused as the HM-801. The HM-801 has no mid-bass bloat, just a nicely presented, linear bass presentation that will sure bring out the best in your subwoofer.
Midrange:
There seems to be a slight forwardness to the midrange presentation of the HM-801. Surprisingly, it doesn't make it too fatiguing since the Westone ES5 themselves too have a forward midrange. Vocals on the HM-801 have such a natural weight and presence to them I cannot find in the iPod. It's easy to just sit back and admire the instruments through the HM-801 while through the iPod, I become analytic and pin-point every flaw, mainly vocal sibilance. The vocals through the iPod have a lifeless and sucked out presentation that really hurts the musical enjoyment for me. The coherence between the lower midrange and upper midrange is also poor on the iPod. When the vocalist pronounces anything that is likely to cause sibilance, the actual sibilant note seems to be higher in db than the lower harmonic notes. Through the same song, with the HM-801, the voices sound a lot more smoother, vivid and realistic. Guitars have such a beautiful presence and the overall power behind every instrument is easily felt. Due to the HM-801's improved midrange clarity, even though I'm less critical/analytical while listening to the HM-801, I can understand what the vocalist are saying a lot easier than through my iPod.
Treble:
Smooth, precise and natural is the words I'd use to describe the HM-801's treble. The iPod has more emphasis here, which in my opinion, gives it that hazy, cold and lifeless sound. Some may call it the "digital" sound. At first, this sound is exciting, but after a while, it becomes fatiguing. The HM-801 has gotten a lot of hate because of it's treble roll off. It's okay that you want the most accurate source according to graph sheets, but in terms of musical enjoyment and realism, neutral isn't the sound you most likely want. Though the HM-801 has less treble energy than the iPod, it still manages to produce a larger soundstage with a more detailed and fine tuned imaging. Every note carries a convincing weight and presence that is non-existent with the iPod. The sense of ambiance is absolutely breathtaking with the HM-801 along with an even darker background than the iPod. Simply put, the treble and overall sound from the HM-801 is just effortless.


Summary:
The Hifiman HM-801 isn't the end be it all audiophile DAP. It still has it's share of flaws that keeps it from being #1 just like any other mp3 player. To some, this player may seem like a giant waste of money or a marketing scam. In my opinion, if you love music, have high end IEM's or portable headphones and want to upgrade your portable source, take a more in-depth look at the HM-801. The HM-801 is an exceptionally great sounding DAP with a powerful built in amplifier that can drive a wide range of full sized headphones to a respectable degree and a legendary built in DAC that is highly regarded as one of the best DAC's ever created. I'm glad I took the dive and bought this DAP.
Highly recommended!