I just got my HiFiMan HM-101 portable USB 16 bit 48.0 kHz DAC and headphone amplifier from Amazon for less than $27 bucks. I bought a used model in like new condition. I have two System76 Leopard Extreme and Lemur Ultra Thin PCs running Ubuntu 12.10 64 bit and it works. It shows up as PCM2702 when I plug it in to my Lemur. I hooked up a variety of headphones and IEMs including my AKG K 702, Etymotic ER-4PT/S, Ultimate Ears Ue-18 PRO, and AKG K3003i plus Grado SR-60i. It's got a full-bodied warm sound that is euphonic and very forgiving. It is not accurate or neutral, but I did not expect it to be so for less than $27 bucks. I am using a 3' foot long USB mini B cable. It is not a high end audiophile boutique cable. I'm done with that ******** for good. It's really small and portable and it's about the size of a match book lighter. It's got a bright blue light when it is plugged into a USB port. It works with USB 2.0 and 3.0 ports. I am testing the headphone jack rather than the line out jack. I have little use for the line out jack right now. I find that it is powerful enough to drive low impedance headphones under 100 Ohms with quite a bit of power and high volume. Since I use a long mini USB cable, I don't have any problems with EM/RFI interference, but there is an audible background hiss that smears the music. It's pretty apparent with my Ue-18 PRO CIEMs which have a very low impedance. The ER-4PT also picks up the background hiss, but it disappears with the 4S adapter. The AKG K702 picks up the background hiss, but it is diminished. The AKG K3003i picks up the background hiss and it's prominent.
I got this because it's dirt cheap and I only need 16 bits 48 kHz resolution USB DAC and a headphone amplifier that is USB bus powered. I listen to Spotify Premium using Vorbis codec at 320 Kbps and Fraunhofer or LAME 3.99 --preset-insane 320 Kbps CBR MP3s which constitute my entire music library. I have 15,124 MP3 tracks totaling 153.00 gigabytes. I think that it does work well with the Grado SR-60i because it matches the Grado full-bodied warm house sound. For highly accurate, neutral, reference grade headphone and IEMs, it's not the best match, but it does provide a full-bodied, liquid, warm sound that is easy to listen to for long periods of time especially when listening to lossy codecs at high bit rates. It's a nice colored sound that is eager to please many listeners.
Compared to the built-in DAC and headphone amplifier in my System76 Lemur Ultra Thin notebook PC, it's miles ahead. It tightens up the bass, it has a clear mid range, and it has smooth albeit rolled off trebles with improved pace, rhythm, and timing and improved resolution and detail retrieval. It's also not tonally balanced. The bass is a bit thick and congested compared to higher end DACs. It places a warm, liquid, burnish over the sound that is easily identifiable. For most popular, rock, rhythm and blues, jazz, funk, rap, hip-hop, and electronic music like dubstep, it's pretty good. I wouldn't use it for critical listening sessions where accuracy and neutrality are paramount to make important judgments about sound quality, but it's fine for YouTube, Hulu, Netflix, Amazon Prime, Spotify, MOG, Pandora, Rdio, Slacker Radio, Last.FM, Magnatune, Songify, Sirius XM Satellite Radio, etc.
I'm used to ultra high end audio components and systems. Yet, I don't feel let down by the HiFiMan HM-101. It's definitely a keeper in my collection and it occupies the low end budget digital source component. I think that this is the lowest priced commercial product of its kind or class. It's a nice product that is worth the very low price if you plan to give it as a gift to someone else or a kid with a budget laptop who wants to listen to the latest teen pop music.
I like it, but I don't love it. I give it a general recommendation, but I am not enthused about it. If you're looking for a very inexpensive upgrade for your laptop PC, then this is the only choice for under $40. It's a pretty good value and it's compatible with Microsoft Windows, Apple Macintosh OS X, and GNU/Linux plus BSD.