Pros: Small, inexpensive, mobile, good design
Cons: Not constructed rigorously, some noise issues, bright
Hifiman HM-101 Portable Sound Card An inexpensive way to turn any USB capable computer into a hifi station.
So I received the HM101 and put it through some work.
Small, wow, comes with everything you need. It's so tiny. Key chain tiny. This is good. I like small when it comes to this because it's really portable. It comes with the USB cable and the unit itself. Nothing else needed.
It's inexpensive, so expect it to feel that way. It creaks and feels like it compresses when you press it or handle it. It's not super cheap feeling, but it definitely isn't made to withstand wear and tear. So you should take care of it, or it will be a loose little thing. The connections are all tight, so that's good. But the plastic covers move and make noise if you touch them harder than just a gentle brush. I'd had hoped for something reinforced. It feels like there's nothing sturdy behind the black plastic covers, you could push through. The unit is very light weight, it feels like you could blow it out of your palm with an exhale. It's not a very dense object.
It's external, so style matters. I think it's a gorgeous little unit. I like the classy look of most of Hifiman's stuff. It has a retro font with a classy overall modern appearance. The blue LED is nice, and not overbearing. Looks good. Style points.
I plugged her in and she was detected immediately. Showed up as "Burr-Brown Japan PCM2702" speakers. I simply set as default (or selected in Foobar2000 as my output device) and was playing music. Very easy to use, fast response, works without any trouble. This was tested on Win 7 x64. It has a phone jack that is amplified. It also has a line out, so you can use it to output to another more powerful amp or to a set of powered speakers. I tried it out with my M-Audio AV40's and it worked great (powered monitors) for a compact external system that can plug into any laptop/netbook. I also used it to output to my other amps and that worked fine too. Ideally though, if you're just looking for a DAC/AMP this is all you need, but if you're using it to simply output to another amplifier, I would look at a better more discreet DAC option with a different connection type (like optical/SPDIFF, I would probably get the Fiio D3 instead if simply outputting to another amp).
The sound is warmer than I expected, it really was a musical sound, less of an analytical sound. However, the noise floor was really high I found. Also, your USB port has to be very sturdy or you'll hear it. I tested it on several different computers and several different USB ports. I found that if the USB connection wasn't really, really tight, it would add sound as it moved, so I found that to be an issue on older machines or heavily used USB ports that are not very tight after a few years of use. In a really tight USB port, I had zero issue though. The noise floor is high as I mentioned, it's the first thing I noticed. Compared to some of my other DACs which are dead silent when I have something plugged in or playing quietly. I can hear a lot of hiss and noise floor from the HM101 regardless of what headphone I plug in. It's not super loud, but it's definitely noticeable when you come from a good DAC that is silent. I imagine this might have something to do with gain and you cannot change any settings on the HM101, so that's just how it is. I plugged in some SRH940's to reveal any detail the HM101 would give off that isn't in the recording, and boy it did, there was that noise floor. The noise/hiss was less noticeable in other headphones I used that were more forgiving of source. If you have analytical/detailed headphones for primary listening, I wouldn't use this DAC/AMP. It's just too noisy for me in combination with a headphone like that. If you have some more musical/warm headphones that are a lot better with noisy sources or simply forgiving of source, you will have a better listening experience with the HM101. Granted, this is still better quality reproduction than typical onboard sound for a lot of laptops/netbooks. But, I'm not so impressed with it compared to discreet soundcards. I have a Xonar DG and Auzentech Forte and didn't find it to compete at all with either of them. So someone with a full size machine would benefit from a different device unless they strictly wanted a mobile tiny device like the HM101. On a laptop/netbook where upgrading onboard is not an option, this HM101 makes good sense. It gets you off the noisy onboard. However, again, you still have to deal with USB noise and potential added noise if the USB port is not very tight or connective.
Sound itself was good. Detail came across well, I had good crisp highs, good mids, clarity, and the overall signature was warmer than some other sources I've compared to. I wouldn't call it special compared to things that cost equivalent or higher than it though. It's not better than a typical sound card. But it is better than a bad quality onboard sound option. Note, some onboard options are actually really good and superior to this unit. I think the highs are a little bright, I noticed some of my headphones gained some edge to them that was not previously there.
The amp side can push headphones quite nicely. It won't take care of maximum impedance inefficient insensitive headphones. But it will power most headphones without much effort. It even can power an ortho. I plugged my HE-500 directly into it with an 1/4" to 1/8" adapter and it actually played music just fine. It was a little bright sounding compared to normal, and I didn't get any clipping. I did notice I lost a lot of volume in the low end, but I was still able to get low tones without clipping. So it can drive even the HE-500 if you wanted to go portable with some high end orthos. Kinda cool. It won't be driving them to their full potential. But it's definitely capable.
I had to turn down the volume on my SRH940's to about 25% on FooBar2000's volume slider. At 100% it's way too loud. So this little guy has a lot of room to output volume.
I plugged a pair of Sennheiser HD650's to test higher impedance headphones and of course, see if it could power the sleeping giant. It powered them. I had to put the volume slider to 100% to have just a hair over my listening volume, so it was just adequate. I definitely noticed it was brighter on these headphones compared to a better balanced DAC. I mean, bright HD650's? I was getting fatigue from some dubtrack from some high pitch tones and synths. So that definitely gives me the impression that the HM101 adds significant brightness to the highs of headphones (which explains why the SRH940 was so harsh to listen to on this HM101 since it starts out so forward as it is). The bass was definitely not coming to town. It was muddy, clipping a little, and not controlled. So the HM101 cannot power mid-impedance or high-impedance headphones with authority. I'm getting bass, mind you, it's playing the tones, but the control is clearly not there when I compare it to a sufficient amp. I wouldn't put some 250 / 300 / 600 ohm headphones on the HM101. Basically anything under 250 ohms would be ok likely. This is right in line with most base sound cards so that makes sense.
I felt like it's ability to drop power on a low end tone wasn't sufficient. I noticed a lot better impact in low tones (using dubstep tracks) from other devices. I was able to get the low tone played, without clipping from the HM101. But, it definitely lost impact and had less presence that various headphones on more capable amps had. This is not a con really, since this is an inexpensive portable combo unit. It's actually impressive that it's able to do this much with most of my headphones to begin with. But don't expect it to drive most headphones to their full potential. It will get them nearly there, but not all the way. Some headphones really are sleepy after 98~99% of their potential until you give them ridiculous amounts of power.
Conclusion & Thoughts:
For the money? Sure, I'd recommend this. It's a good little DAC/AMP for someone that wants something simple, small, and portable. I would not recommend it for someone with a headphone that has significant power requirements. If you have a pair of low impedance and sensitive headphones, this will work great. I think it pairs poorly with detailed or analytical oriented headphones. That is, unless you want to hear a lot of stuff that is not very pleasant, but if you're critically listening for artifact and issues with a recording, it will definitely reveal them to you. That's good or bad depending how you look at it. Based on how it sounds, I would not put it with things like the SRH940 or the KN6400. I would also not put it with a Grado of any sort. It will just hurt. I would however pair it with already relatively dark or warm headphones. It adds brightness and warmth as it is, so they won't be as bad when paired up. The warmth is in the mid/upper bass, not the lower bass, it's power is insufficient to enhance (color) the sub bass, but that's ok, it's not a powerful amplifier, so it's not expected. If you're using a computer and you want a good DAC/AMP and you can install a sound card, I'd suggest you get a Xonar DG instead. It's better control, has dolby headphone, etc. Simply a better investment for that situation and covers more headphones. If you want a portable DAC/AMP for low impedance headphones that will work from your laptop/netbook or on someone else's computer when you move around or to take to class, school, work, then this thing will definitely fit the bill.
If I had to scale it, I'd say it's about a 6 out of 10 overall. So, better than average, but not something I'd call exquisite.