I wasn't expecting much from the Hifiman Express HM-101; it's just a $39 outboard USB digital-to-analog converter and headphone amplifier. Well, this tiny USB-powered (it doesn't need batteries or an AC power supply) device definitely pumped up the sound of my Audio Technica ATH-M50 headphones! They sounded significantly better with the Express than they did plugged directly into my Mac Mini's headphone jack. Sure, the Mac's sound is perfectly acceptable--until you compare it to something better.
The Express is a lot better.
Before we go any further, the Express isn't just for headphones, it also has a line-out 3.5mm jack you can run to a set of desktop-powered speakers, like myAudioengine 2s. DAC resolution isn't specified, but it's probably 16-bit/48-kHz.
Switching over from the computer's headphone jack to the Express, the first thing I noticed was that the Express could play a lot louder. That's great, but when playing drummer Ginger Baker's "Going Back Home" CD at equal volume levels from the computer and the Express, the Express unleashed more of the drummer's hard-hitting dynamics. The computer squashed his sound, especially Baker's mighty bass drum. Wow, the little thing delivers. If anything, the Express errs on the side of too much bass fullness, which isn't such a bad thing.… Read more