The HM-602 is a portable digital audio player made by HifiMan Chinese producer. The player uses a Philips TDA1543 NOS DAC chip, which is the easiest multibit chip to implement, within those in TDA line (TDA1541, TDA1543, TDA1547…).
The HM-602 feels like a vintage DAP coming from the years of Rio Karma, but is actually much lighter than one would expect. The plastic feels fragile, but lightweight. The stock interface is a bit clunky, but Rockbox has been implement on the DAP. The internal storage is 16 GB, and there is an SD card slot.
The player is thick and difficult to keep in a pocket. It would require a money belt or a small bag to be carried.

Sonically, the DAP approaches a very agreeable phylosophy. Many portable music players tend to sound U-shaped in order to give bass and details to the listener, or present “hardcoded” audio processing in order to enhance the soundstage.
The Hm602 has a warm sound and natural treble roll off. Such traits are pleasant but can pose pairing issues with certain iems. The full tonality makes it couple extremely well with flat / bass light /bright earphones.
I did a mini meet with a friend who carried Westone 3, and they didn’t sound as good with the Hm602 player, because they exagerate the response in the middle/low range of the sound spectrum.
The player manages to output the same level of detail as “U shaped” Mp3 players, without sounding bright, harsh, or lifeless.

With the Hifiman’s RE262 canalphones, which I had bought in bundle with the HM-602, the midrange was too much, although the tone was very “cohesive”. I believe the biggest reason of existence of the HM602 is to act as the right dap for neutral high-end IEMs/earphones, like Etymotic ER4, Jh13, HifiMan RE0, Yuin OK1 and OK2. The Jh13, specifically, are a “magnifying” glass to the source and they are wasted on regular players. The JH13 enjoy a source offering rich midrange, since they are exaggerately transparent in the mids (borderline to being recessed).
It also sounded good with the Thunderpants, a custom wooden headphone based on the orthodynamic Fostex T50RP [more info about it on Head-fi.org, where it has been conceived].
The HM-602 would pair less well with IEMs like Shure SE530, the aforementioned Westone 3, Westone UM3x (which I recently owned), Triple.fi 10 Pro, Klipsch Image X10: all these have already more than enough bass / lower-midrange warmth to be a good coupling with the HM-602.

Finally, a couple of words about the internal amp. It’s powerful and can power sensitive full size headphones, when set on high gain. Unfortunately, when trying it with the Thunderpants, I felt that the sound was a bit muffled; using a Mini^3 portable amp, for additional power, made the sound much better and clearer, and closer to the home setup I had at the time, based on Museatex Bitstream and CKKIII amplifier.

Based on its tonality, although I didn’t listen to them at the same time, I think the HM-602 would pair well with Audio Technica AD2000, a favourite of mine, bringing more analogue pleasure to an already involving headphone with raised upper mids.