The Hifiman HM-601 is my favorite portable player for the following reasons:

*Sound quality--it has a warm, smooth, very musical, very analog sound. Detail and clarity are good, but this isn't the best player to listen to an audiobook, perhaps. Instead it's geared for music, and it's extremely good at it.

There is an effective 5 band eq if you want it.

*Soundstage--it's the only player I have with a soundstage that rivals my best desktop amps. It's very satisfying in this regard.
*Power--this player has enough power to drive full-size dynamic cans with as much power and authority as you could want. My Q701 is my favorite pairing, to take advantage of that soundstage. My 250 ohm DT880 also sounds excellent. The 601 does not power my full size planars very well (HE400, LCD2, Alpha Prime), but that problem is easily solved by using the line out with another amp. It does fine powering the Sine on its own.

There are no major downsides, but there are a couple less than perfect issues. The UI is completely non-intuitive, but it does have its own logic to it, so you will be able to learn to accommodate it without too much suffering. There IS a Rockbox port for the 601 (but not most 601 slim models). The install (and especially extraction) processes are more involved than most, so be aware of that.

It doesn't seem able to play a 24-bit wav file, though 16 bit is fine.

It doesn't pair well as a source for my Stax Lambda Pro electrostatics, in my current opinion. I thought it did at first, but it's lack of detail becomes apparent to me now. That is a unique situation, because it sounds great using it as a source through my desktop amp with just about every other pair of cans I have.

In all it's somewhat of a bare-bones player, with no digital in or out or other fancy features, but it plays beautiful, beautiful, music, and that's why I use it more than any other.

If you are after good sound this is all you need.  There is no need to carry a portable amp. There is enough power drive my 250 ohm DT-990's with power to spare. The sound is full and lush and takes my EIM's to another lever. 
I have the RE-262 and thought they were good. Matching them with the HM-601 brings out their full potential. Tighter bass, crispier highs, depth and wider sound stage.  Over a very crisp clean sound.
My co workers joked around when they saw it and didn't take it a serious DAP saying it looked like it was from the 80's., However the shocked look on their face after they heard it, said everything.

Very nice player, it is my second favorite DAP.
But will be my best player if I update it with RockBox, and that's if we have a stable version!!!

 

Hifiman HM-601 + RE-272

 
 

Story and scope

After the Danish Head-fi meet, nc8000 (the father of our Danish Head-fi society) said Fang from Head-direct had given him a HM-601 + RE-272 to pass on to another head-fi’er who would write a review of the HM-601 together with the enclosed in-ear headphones, the RE-272. I volunteered because I thought it would be fun to compare it to the Hisoundaudio player described above.
 
I was told that a lot has already been said about the HM-602 and the HM-601. So I hope it makes more sense to compare the HM-601 to the Hisoundaudio Studio-I other than just writing a review on the HM-601 by itself - at least that was what I thought. People who are looking to buy the HM-601 will probably find better reviews than I am able to write. So maybe they will consider the Studio-I as an alternative after reading this?
 
I also have not read any other reviews of the HM-601 nor the RE-272. As I wrote above I was perfectly satisfied with my iPod and iPhone as portable sources so I have not had any interest in reading about other portable players. I won the Studio-I in a raffle and I was given the HM-601 for free in order to write a sincere review. nc8000 said that Fang (from Hifiman or is it Head-direct?) did not want to read or comment the review before it is being posted. I think that is a cool attitude. We can always discuss whether paid (with products) reviews on forums like these make any sense because most of those reviews will be positive. But when assessing these two products I can truly say I have no preferences to any of the products.
 
I own both units and I did not pay for any of them. So I am simply going to write what I think and not be biased in any way by what others think of the products. Now to the HM-601…
 

The packaging

I wrote about the nice box the Studio-I DAP came in and the HiFiMAN leaves nothing behind. I think the HiFiMAN box gives an impression of a great product and one you want to unpack and start using. It is not just a cardboard box with a logo outside but also a well-designed box placing accessories nicely tucked away and showing the HM-601 in one side. Well done – I like it!
 

 

The build quality and ease of use

Compared to the Hisoundaudio the Hifiman feels like (and is) plastic vs. aluminum. It is not the same luxurious feeling at all. Also the buttons has a plastic sound and feel and it does not appeal to me at all when using the product. I could not figure out how to turn the product on in the beginning because the interface and boot-time is a bit slow.
 
I connected the HM-601 to my old MacBook Pro where all my music is stored in ALAC and AAC. I do know that it does not play ALAC but I would expect it to play AAC. I cannot confirm this from the head-direct webpage. During the file transfer the USB connection is lost spontaneously and the files are not transferred. I tried several times with the same result. I am simply not able to transfer music from my Mac. So that was a bad start for the HM-601.
 
I brought the HM-601 with me to my work where we have Windows PC’s. Here there were no problems connecting and transferring music. I did transfer some of my AAC files I had on the Hisoundaudio Studio’s memory. But the HM-601 did not even show the AAC files stores on the internal memory. I converted them to 320 kbps MP3 in iTunes and transferred the files again and now they did show up on the HM-601 and I could finally listen to some music. I know that ALAC files or 320 kbps AAC files converted to 320 kbps MP3 is double converted files and thus not the best sounding files but I only did this in order to get some files to the unit. This experience is breaking the deal for me with this product. Not being able to use it with my music on my laptop makes this product a no GO.
 
A little flaw I found in this product compared to the Hisoundaudio is that when I plug another source into the line out I can hear two sources playing at the same time, the music from the player itself and at the same time also from the source. On the Hisoundaudio the player automatically changes so that the unit works as an amplifier turning down it's own playback and letting me hear the music from the other source. Do not blame the HiFiMAN this. Why would anyone do that? Well, I did! And I just wondered why it mixes the two sources. It is simply just a bad user experience I can't help but to take notice of.
 
Also when shifting to the next track you have to use the down-arrow and up-arrow for previous track. Once you get used to this I can live with it but I do not think this is the logical way to navigate tracks during playback. This player does not speak my language and it has been outperformed by the way it is constructed and designed compared to the Studio-I.
 
 

The sound

I have been carrying the LISA III around for a long time when I had it. So I can live with all kinds of good and bad sides of a product if the sound justifies it so let’s see if the HM-601 can win me over when listening to it.
 
First thing I noticed when using the enclosed RE-272 a constant background noise is heard and the noise is changing when there is light in the display and changes again when the light turns off. The noise is low but audible and it is not at all acceptable in a product claiming to aim at the audiophile market. This might not be an issue for some people, but I know that some are more sensitive to background noise than I am so it has to be mentioned.
 
The difference between low gain and high gain is there but very subtle. I think it should be a bigger difference in order to drive headphones with higher impedance.
 
A lot has been said about the NOS DAC TDA1543 used in the Hifiman. I like the analog-like sound of the NOS DAC's. I have the cheap MUSE DAC with 4 pcs of the TDA1543 and I like the relaxed laidback analog-like sound and I find it very musically involving. It is a sound that does not cause listening fatigue in my ears even after long listening sessions.  I do not want to describe the sound in details. More reviews can probably be found a lot of other places regarding the NOS DAC sound. But the NOS sound is a compromise if you are only looking for high resolution and microdetails in the music. On the other hand it offers listening pleasure and music played in a way that it sounds like it is played with real instruments.
 
I have tried HM-601 with HD650, SR325i, ER-4S and the RE-272 and they all sound great directly out of the HM-601. The best thing in the sound of the HM-601 and where it clearly beats the Studio-I is in the mids. The mids are so sweet and lush. The bass can be somewhat “boomy” when driving the HD650 and I think the bass lacks resolution and definition. But that is ok for a portable device driving HD650 but in all the other headphones I tried this player sounded absolutely great.
 
The ER-4S seems to be a great match for the HM-601. The detailed bright ER-4S sounds very balanced with the lush and warm HM-601. This combination is true listening pleasure to me and I find it much better than using the RE-272. All in all the RE-272 is not my cup of tea at all. They are too warm sounding to my ears. I am used to ER-4S so that is probably the reason why I find everything else too dark in comparison. I have to say that I enjoy listening to the Studio-I with their enclosed earbuds better than listening to the HM-601+RE-272. Does this mean that the RE-272 is a bad in-ear – maybe not. I just think it has too little resolution and as already mentioned too bass-focused.
 

 
[size=12.0pt]I have tried to focus on the things I didn’t like form this player. But I have to say that even though the sound is not perfect and there are some compromises I still love the sound very much.[/size]

 
"The packaging was very boutique. It demonstrated the fact that head direct is a small company. The pleather box it came in had the bottom falling apart due to the glue unsticking, but it was an easy fix. It came with a chinese power adaptor with a US plug (which means I had to buy yet another because I live in aus). Charging took 2 to 3 hours. It also comes with a microfibre cloth, and decent length usb cable and a velvet bag with strings you pull to close the opening. The hifiman itself was chunky and had a plastic feel to it, but the size was very reasonable. The plastic casing around the directional buttons is raised, which at first annoyed me until I realized how handy it was for preventing accidental button presses.

 

The sound is #$&@#% amazing!! When people described it as musical I didn't really know what they meant, but for me it's simply a cleaner, more original (real/analog, etc) sound. The hiss originally bothered me a little bit but when listening to music at a comfortable level you cease to hear it. Again, the sq is what I bought it for and it really delivers. I am absolutely satisfied with it. Not being able to play anything but audio is great too, because it meant I can save room by deleting album art and m3u files, etc. 

 

I experimented a lot with the hi/low gain switch, and noticed that only the bass and details emerged and the volume stayed roughly at the same level with everything else. I usually keep it on high gain with my Westone 4's and leave it at 2 or 3 on the volume control (btw, having an analog volume control wheel is awesome, i love it). With my BeyerDynamic DT770Pros 250 Ohm, the bass and mids are delightful and the volume can be maxed without being painfully loud. You can feel the air move with each bass note, a very different feel to the bass of the Westone 4 iems.

 

There is absolutely no gapless, not even close. Listening to Cat Power's 'Jukebox' album (192kps) there was a hiss present through out the track, and when it came to the end of the track and the start of the next, all sound (including the hiss) disappeared for up to a second before the hiss kicked in again and the music started. This doesn't bother me much, but it apparently does for other people, as the lengthy threads have documented.

 

I have some high-resolution (24bit) Chesky Reference albums that I put on the sd card (SanDisk 32gb, class 2) that would simply refuse to play. The whole UI would lag and react strangely, teleporting through folders and not playing anything. This doesn't apply to all 24bit music. My greatest sounding recording is Frank Sinatra's 'Sinatra's Sinatra' album. I usually use the first track, 'I've Got You Under My Skin', which is 24bit/96khz (2962bitrate) flac. Frank's voice sounds beautiful, real and there and right in the centre of your head. It almost feels like you're singing. The high hat has lovely delay and detail, the bass is tight and accurate, the instrument separation shines with the brass, woodwind and string instruments. Everything is clear and the recording has been beautifully mastered (I feel like I'm running out of accurate adjectives to describe these qualities). 2 and a half minutes into the track there's an instrumental interlude, and I swear I could pinpoint EXACTLY where the musicians were standing in respect to me. The trumpet was exactly a metre behind and to the right of me. It felt incredible.

 

I also auditioned New Order, Blue Oyster Cult, Chopin's Ballades (by an unknown pianist - nb: i could hear their every breath as well as every emotional nuance of the piano), Death, Echo & the Bunnymen, Joy Division, John Coltrane, Deftones, Megadeth, Mozart, The Smiths, Burzum and Fever Ray amongst others. I won't go into details of each one, but the hifiman performed every genre admirably.

 

The battery lasted 5 days for me before I had to recharge it. I listened to it as I was travelling from location to location (eg, work to home, home to music store, etc), so I'm quite happy with the battery life.

 

The UI is normally quick and easy to use. Navigation is a breeze but it does lag when it attempts to play incompatible high resolution files.


My class 2 Sandisk SDHC is a pain in the arse to load up, as the transfer speed is shockingly slow (alas, it was cheap) and on every boot I have to reinsert it, which I don't mind because it satisfies my mild OCD.

 

I let a few people listen to it (partner and friends, one of which is a sound engineer). Received quite a few reactions of closed eyes and smiles, and tapping feet, etc. I myself experienced aural orgasm when I first listened to it, the music really excited me and I reacted emotionally which is great for a portable player. My sound engineer friend commented that he could hear the whole mix of the demo tracks clearly on the hifiman.

 

Overall, very happy. Best purchase I've made this year."

 

Impressions quoted from forum post: http://www.head-fi.org/forum/thread/524012/review-hifiman-hm-601/765