Upgrades are a rare sight to be seen in portable audio. For a vast majority of manufacturers it’s presumably much easier to develop new products. But lately HiFiMAN showed some love to one of its older devices. A brand new life can be put in a discontinued HM-901 DAP. Its second incarnation is simply known as HM-901s. The former was quite the performer and that’s the reason why the latter is this review’s main dish. Enjoy.
Introduction
An upgrade feature might be both a curse and a driving force for a manufacturer. Some companies handle it no questions asked, e.g. Polish and quite known LampizatOr. These people are all about that since their main man – Łukasz Fikus – is a skilled tinkerer constantly working on something and keen towards upgrades in the first place. He improves his circuits and once something new is born and ready, that’s perfectly doable to have it installed instead of old parts. Audio enthusiasts know and exploit that whenever and wherever they can and everyone happy is the very outcome. To have a $18’000 DAC upgraded to latest version and not sold for half of that in order to get the latest goods? Yes, please. 
But still, many manufacturers simply like to develop new devices and warranty related support aside, nothing happens to older ones. As long as a new creation has the obvious thing improved, sound quality that is, everything is OK in my book. LampizatOr’s upgrade policy is unique but not the only one. Picture Norvegian Hegel, this company also upgrades but in a different, more common fashion. From one model to another a big quality improvement is always made. Despite the fact that CEO Bent Holter has been in audio industry for many years, he’s still able to improve his own designs. And knowing this, many Hegel owners will perform leap of faith as they more or less can predict the outcome. That’s fine as well if someone asks me.
Things are much trickier in portable business. For instance, when FiiO’s second DAP generation hit the market, both old and new devices looked quite like children from the same father. But the latest addition still had both a chassis and innards revamped, more refined look was the outcome. One could easily see that there was much more to it than merely a sticker with MKII writing on it. iFi Audio did similar thing, Thorsten Loesch improved his own work as well. But is there a company that’d grant us possibility to have a discontinued product reworked to a brand new state and loaded with most of latest functionalities? In such scenario only HiFiMAN comes to my mind. On this manufacturer’s official site there is a $499 service which turns old HM-901 model to HM-901u, whereas HM-901s is brand new unit. That one small letter, be it u or s, actually changes quite a lot. Before we go into tasty details let me just point out that only HM-901 DAP in particular can be revamped, no other product from dr Fang Bian’s line-up. But what counts the most is that none of HiFiMAN’s competitors provide us with such service. I’m all in.
Design
The product’s box is decent to say the least. Stiff cardboard covered in leatherette woks like a charm and quality wise is much better in comparison to plastic alike leather imitation HiFiMAN used on boxes for many years. Good stuff, there is no reason to complain. Inside the box there’s a fairly short manual, this is the very first thing one sees. A rather large and heavy AC adapter comes in as the next one and desktop battery charging platform follows. This is a really cool feature yet it’s a pity that additional battery isn’t a part of the package. This would certainly brighten up the day for many people. Moving on, a warranty card is another mandatory addition, but coax and a line-out combo adapter inside the box isn’t. This means that HM-901s can be used as a digital transport, therefore feeding a desktop d/a converter with a digital signal is perfectly doable and works like a charm. This DAP can be also plugged to a pair of mono amplifiers matched with passive speakers. In such role it handles both digital and volume control duties. Lastly, an USB cable is also a part of the whole.
HiFiMAN HM-901s looks more refined and sleek in comparison to its predecessor. The design is less rough visually. The enclosure is now aluminium all the way, which is good as older one was fully plastic. All HM-901s surfaces are flat and I believe that this is what makes it look much cleaner. It’s safe to say that its first generation gave the toy alike impression whereas latest one on the contrary. The device measures 11,4 x 68 x 26 mm (H x W x D) and weighs 250 g, therefore is plainly big and heavy. Several things have changed in comparison to previous version. The click wheel has been improved as it works much smoother and isn’t wobbly any more. Let me point out that it was the only element that broke during over two years of my HM-901 usage time. Yet it made the device useless in the process. All five buttons nearby (home, play/pause, fast forward, rewind, return) protrude a bit more and that’s a major improvement as these are simply easier to use. On the device’s right side there are two switches; power on/off and lock. Something’s missing. HD/vintage and low/high gain switches are there no more, though the latter function is accessible from the menu. 
The resistor based volume knob is familiar, yet easier to use and loaded with more steps. It’s nicely implemented this time from visual standpoint, without any artificial leather nearby. This is a major plus for many people surely. On the device’s left side there is a SDXC memory card slot and it’s worth mentioning that HM-901s has no built-in storage. For the asking price that’s a major ouch right there. Though the word is that additional circuitry influence the sound negatively. And lastly, on the DAP’s bottom there is a famous connector, the same as usual. To many people it’s highly unpractical. No typical USB input? But why? Well, for several reasons. HM-901s has actually two batteries inside. Regular USB socket can’t handle these and bulky AC adapter is still needed badly. Charging aside, this one pesky connector HiFiMAN uses for years also enables data transfer plus digital and line-out. Yes, USB is much more convenient yet the compromise had to be made somewhere. Moving on, on the product’s top there are now two 3,5 mm outs; one balanced and one regular. No more switching between these and that’s a very good idea if someone asks me. Though I’m not all that happy about two screws instead of rear cover’s locking mechanism. Yes, now in order to change amplifier module, screwdriver is a must. Fortunately proper tool it’s included in the package. But still one has to carry around a DAP, an AC adapter and a screwdriver too.
The product’s chassis is now fully aluminium and sharp in certain key areas. I can live with its front ledges handled in such way yet I don’t understand why there are no roundings near the volume knob. This is highly inconvenient if one wishes to operate it with his/hers index finger from the device’s back. That’s one of my biggest gripes with HM-901s from usability standpoint. Another one is the display, this one hasn’t changed and still is a reason good enough to curse extensively during this DAP’s outdoor usage. Not to mention that not much can be done in order to make it brighter via menu, sadly. Ouch. The interface hasn’t changed at all, it’s good ‘ol Taichi UI. The options are quite standard, namely user can set gain low/high, turn coaxial out on/off, shuffle and repeat music, set sleep and auto power off timer, choose preferred language, use digital filter and that’s about it. Files can be browsed via folders, artists and so on and there is no reason to complain with one exception. The wheel’s scrolling speed is fixed and that’s extremely tiresome as it is slow. One rotation equals one row. On top of that, during regular usage it has a rather nasty habit of returning one line instead going forward. This is very annoying and I sincerely hope that something will be done about this. 
Lastly, the device now supports DSD files and it can go to sleep mode, which is a nice feature. From this state to being fully operational it takes only three seconds, just as manufacturer declares. Though in this mode the battery is also used and eventually it will deplete. Ah, and the innards! HM-901s has two full-sized ES9018 d/a converters on-board, not K2M versions, therefore nothing’s changed here. But new crystal oscillator is mounted and the analogue section consists of a pair of OPA627 and OPA2107 operational amplifiers now. Original HM-901 model had only the former included. Its successor is sold in silver finish only and that’s a slight bummer as lots of people would like to have it black. The sample, full s version and not an upgrade, was provided to yours truly with MINIBOX Gold amplifier card. That one is also quite new. The battery lasts about 8 to 10 hours, it depends on the load.
Sound
HiFiMAN HM-901 with its balanced amplifier module served me well for years. It finally died, yet this was my fault only. If it wasn’t for an unfortunate accident, which included rather nasty drop from several meters, I’d probably still use this particular DAP. UI, OS and bulkiness aside, it sounded plainly wonderful and very peculiar. HM-901 had plenty of power, it drove vast majority of headphones I tried over nearly three years. Not only to satisfying SPL levels, but often also quality wise. HiFiMAN’s flagship offered unquestionably the most authoritative sound among DAP-s this editor’s very ears have heard. There wasn’t and to my knowledge still isn’t any portable device of this sort, which would sing with more directness and sheer force. These were HM-901’s key features, said product was tuned to behave like an American muscle car from the very beginning. And because of that feature alone it stood out of the crowd. Yet this aspect wasn’t excessive. Once gentler music played, the portable performer was able to deliver mellow performance as well. Overall it was a rare case of tamed, fully controlled beast no matter the scenario. It’s worth to know these things as HM-901s isn’t equipped with a completely new circuitry, on the contrary. Therefore entirely revamped sound signature is off the table.
HiFiMAN HM-901’s sound wasn’t all about authority and nothing else. Exceptional clarity came with it. I can’t recall even one situation where this DAP’s performance was veiled. Said features led to transparency, previous flagship was merciless for poorly recorded tracks. At first it was somewhat overwhelming. Some recordings which used to sound good or average on most of portable devices, with HM-901 sounded rather poorly. Especially in terms of saturation, texturing overall. Punchy, detailed and clear? Yes, but of course! Yet often with metallic tint, which is an effective joy killer. Unless one is into this kind of a show, that is. Moving on, the next big feature was quite expansive, yet exceptionally coherent and multilayered soundstage. Things were very alive there, tangible and of proper size. Everything clicked in very airy and easygoing space. Though one aspect stood out of ordinary. The midrange, at least some parts of it, e.g. electric guitars, was served rather close. Normally I’d say that this isn’t the way to go, that it won’t work. Yet HM-901 was able to pull this one off as lots of things were going on on the sides and behind the very first row of musicians. That was a rather unique, singular combination of intimacy and soundstage expansiveness I haven’t heard in any other DAP thus far.
Now I tend to think that this was a meticulously planned measure and a part of a grander scheme. Let me elaborate a bit. Curiously close midrange was one of key features and audibly emphasized upper bass was the other. My take on the case is that slight bump in its mid region boosted HM-901’s energetic approach even more. Now when these features were fueled by sheer energy, exceptionally fun giving and direct, yet refined sound was the outcome. Dependencies of this sort don’t happen by a mere coincidence. Someone in HiFiMAN had planned all this from the very beginning. And it simply worked, HM-901’s sound is very memorable one, unique on many levels. It never got dull or lifeless. I can’t recall even one DAP which would combine elements mentioned above in such way. Point being, HiFiMAN’s previous flagship had a very strong character, dare I say… personality.
To make things short, HM-901s sounds about the same, which is a very good thing. Punchy approach is heard once more, things are neatly controlled, tight. Bass is again powerful, complex and greatly extended, yet never wobbly. This DAP’s tonal balance is again shifted slightly upwards, but not much. Just enough to make the sound greatly detailed, yet without excessive illumination and sharpness in upper parts of audible FR. These are superbly extended and textured. Midrange is again quite close to listener’s ears, the very same instruments actually. Soundstage doesn’t disappoint as well. It’s airy, well-organized and simply spot-on accurate. The presentation is clear, any kind of veil is non-existent. Again. So what has changed, if anything?
Yes, one aspect alone; elevated richness. Things got heavier and this is probably MINIBOX Gold amplifier module’s input. Let’s not forget that HM-901’s description was based on HiFiMAN’s balanced card. The new model sounds a bit sweeter and rounder, yet soundwise all key features of its predecessor are as apparent as before. I can’t say whether feeding the original HM-901 with latest amplifier card would net the same result. Presumably it could happen. But for now let me just say that HM-901s sounds more alive. It can be heard that more meat on them bones happened, the sound got slightly less contour in favour of saturation. That’s the main difference. Yet not to a point where this aspect alone would be considered as said DAP’s main trading card. Swiftness, clarity and detailing are the main performers. Latest model’s sound is as fun giving as the one vanilla HM-901 delivered, yet I believe it got more mature, refined. Because of density increase, the presentation is slightly less raw, yet that’s my subjective take on the case. In the end it might be about synergy, though. All pieces of the puzzle indicate that thicker sounding headphones presumably would fit balanced module better, whereas airier and detail oriented models probably are a better match for latest amplifier card in HiFiMAN’s offering. These are my guesses based on what I know, remember and have heard thus far.
Individual headphones/earphones mix’n’match description should go in here. Yet instead of doing so extensively, let me just point out that HM-901s has a character this strong, that it’ll always be present regardless of what’s plugged into its 3,5 mm out. The only setup worthy of additional commentary is the one which involves HE-1000. The DAP handled these headphones surprisingly well. The outcome wasn’t better in comparison to e.g. Xonar Essence III and Questyle CMA800R combination, yet respectable nonetheless. Said planars got enough juice to sing quite effortlessly and without any kind of shakiness in lower FR parts. All the tasty details were there and great soundstage HE-1000 is known for was also in check. With a decent desktop performers, HE-1000 paints more precisely sketched instruments in even bigger and more accurate space. Things become also faster, punchier and denser, yet equally precise. But subjectively, HM-901s and HE-1000 is a quality semi-portable combo I was perfectly happy with. This DAP also surprised me as on paper there’s no synergistic interaction between its sound profile and the one of VE5 CIEM-s. Yet it worked and in truly marvelous fashion. I suspected overly bright and contour performance. Smoothness, full low end and brilliantly lively midrange was the outcome instead. Meze 99 Classic was too bass-heavy for this pair of ears, supposedly due to certain frequencies elevated too much. Yet the rest was of quality.
Summary
It’s undeniable that HiFiMAN’s focus is sound quality above all else, there’s no room for a compromise and HM-901s stands as an additional proof. Knowing a fair amount of said manufacturer’s products I’d be surprised if things were any different this time. Yet it can be seen that this company evolves, moves in the right direction. Said DAP isn’t perfect, yet on many levels surely better than its predecessor, perfectly usable this time. Aluminium chassis is a nice and desired improvement, OS is more stable and thanks to physical buttons plus wheel revamped, interaction with the device is nicer overall. Though something should be done about sharp edges here and there. All things considered, noticeable progress happened, therefore good job.
HM-901s still won’t deliver Astell&Kern alike experience usage wise, yet thanks to its sound quality it can compete with every DAP there is, no matter the asking price. Various amplifier modules make it quite versatile in terms of what headphones/earphones one can use. Extensive range of viable choices is the obvious upshot. Latest MINIBOX Gold card is a very good addition to the main product indeed.
To answer the question whether HM-901s is worthy of your attention, individual needs ought to be prioritized. If balance between UI, sound quality, weight, portability, battery life and so on has to be maintained, look elsewhere. This DAP is made for ones like yours truly, who can live with its bulkiness, troublesome display, quite hot operation and other things of similar sort. It’s made for a music enthusiast of the heaviest calibre, who’s after energetic, punchy and direct sound on top of all else. Yet of quality, transparent, lively and smooth, never boring and highly involving. Make no mistake, HM-901s is a rare specimen, it sounds like no other DAP. That’s why I simply encourage everyone who’s into this kind of portable hardware to give HiFiMAN’s latest a go and be amazed by how well it performs. Soundwise it doesn’t get any better than this in DAP’s department. Different? Yes. But not better. ‘Till next time.
Associated equipment:
- Headphones: Meze 99 Classic, HiFiMAN Edition S, HiFiMAN HE-1000, Vision Ears VE5
- Portable sources: Pioneer XDP-100R, Lotoo PAW 5000
- Headphone cables: Forza AudioWorks Noir Hybrid
Retail prices of reviewed components in EU:
- HiFiMAN HM-901s: €1’499
- MINIBOX Gold amplifier module: €299
Manufacturer: HiFiMAN
