The excitement surrounding the HM-602 was pretty high, and not long after that I began to plan a comparison article of the HM-602 to the HM-801. Of course another chinese player by the name of QLS QA350 is starting to gain some solid fanbase, even in my local community, so I thought of making it a three way review. Soon after that, I remembered that Ibasso released the Boomslang portable DAC not long ago, so why not throw that into the mix as well? I thought the four is a pretty solid number representing the current crop of Hi-Fi portable sources. Lastly, I threw in a popular USB DAC, the HRT Music Streamer II+ just to see where these portables stand in comparison to the desktop/USB DAC market. Many thanks to my buddy Sem for the portable players. Thanks to Hifiman for the HM-602 sample.

Since this is going to be a serious shootout, I prepared accordingly:

• Quality recording music were used: Buena Vista Social Club, Beethoven 9th Abbado 4/2000 24/96 DDD recording, Mahler 2nd Tilson 2004 DSD recording, and Stockfish Record’s Art of Recording.
• A special mini-to-RCA cable using my reference interconnect cable and a matching pair of RCA interconnects for the HRT MS2+.
• 2-ch Beta22 amplifier
• Sennheiser HD800
• All files used are of WAV format, because the QLS don’t take any other format but WAV.

There are two more things to take note:

• The QLS QA350 has been modded by the owner, where he replaced some of the stock no branded caps with some Nichicon ones. Modding the QLS apparently is getting quite popular among its owners.
• The Ibasso DB1 Boomslang DAC comes with the stock 6-pin Hirose connector cable. It would be ideal to build a 6-pin Hirose to RCA cable, but since I don’t have the connector in stock, I couldn’t. Hence I had to use the DB1 under this configuration: DB1 Boomslang DAC -> PB1 Toucan AMP (low gain, maximum volume) and take the output signal after the PB1 Toucan amplifier.

Let’s move on.

Portable Sources Shootout

The set up is as follow:

• HM-801 via lineout to Beta22, HD800. HM-801 direct to HD800.
• HM-602 via lineout to Beta22, HD800. HM-602 direct to HD800.
• QLS QA350 via lineout to Beta22, HD800. QLS QA350 direct to HD800.
• Ibasso DB1 via balanced out to PB1, via headphone out to Beta22, HD800. PB1 direct to HD800.

HM-801 vs HM-602
The general soundstage is quite similar to the HM-602, but the subtle improvements are very evident from the first moment. Soundstage size is deeper and wider on the HM-801. And going back to the HM-602 after the HM-801 makes me feel that the soundstage is abrubtly cut off at the edges, where the HM-801 has a more progressive cut off at the edge of its soundstage. Detail level is definitely up, very rich micro details that you don’t hear on the HM-602. The treble extends higher than the HM-602, the vocals richer and more crisp. Bottom end is weightier and there is more low bass presence.

As a result of the treble extension, there is more sibilance on the HM-801 than on the HM-602. I also find vocals to have better presence on the 602 than on the 801. Moreover, while the additional bass weight and low bass is welcome, the transition from midrange to bass is actually smoother and more linear on the 602. I think overall the 602 has a more likeable sound signature, while the technicalities are still a little short from the bigger brother.

The HM-801′s headphone out also has quite a bit more voltage swing than the HM-602 on a high gain setting, enough to make a difference between “quite loud” to “ear piercing loud”.

HM-801 vs Modded QLS QA350
Here is a serious attempt to take the crown from the HM-801 from QLS. Not bad at all, considering the QLS cost a fraction of the HM-801. As long as you’re willing to live with the impracticalities of an even bigger size, the anemic user interface (more on that later), strictly .WAV only compatibility, and the tiny screen display. Ignoring all the other aspects of the design, however, the QLS do have a fairly solid sound signature — so good in fact, that some people in our forum prefer the QLS to the HM-801.

Technicalities wise, the HM-801 remains the King, and quite by a significant margin. Soundstage presentation is more real on the HM-801, low level detail, refinement level, frequency extension, the HM-801 is quite a step up, similar to how the HD800 is to the HD650. You also have to remember that the QLS have been modded to have better capacitors than cheap stock ones, and yet the difference is still not subtle. The HM-801 sounds far more richer, especially on the low level details and treble extension.

HM-602 vs QLS QA350
Moving to the HM-602 from the HM-801/QA350 comparison, it’s again evident that the HM-602 is still under the HM-801 in terms of technicalities. Interestingly, compared to the QLS QA350, the HM-602 has quite an edge. Better soundstage depth though smaller width, better detail level, a fuller and smoother midrange (very nice), and a more believable ambiance than the QLS’. Though I would like to have the HM-801 better treble extension on the HM-602, the HM-602′s treble actually works better for most music as it is more sibilance free.

The only area where I prefer the QLS’ headphone out is the gain level that matches the HM-801, leaving the HM-602 with the least gain among the three.

Ibasso DB1 Boomslang DAC (Coaxial)
The Ibasso DB1+PB1 combo represent a unique entry. It doesn’t work on its own and requires a separate portable transport before it can work as a true portable source. In this comparison, I used the QLS QA350 as a transport, connected to the DB1 coaxial input. The DB1+PB1 combo is surprisingly very good, clearly above the QLS and slightly better than the HM-602, but only coming up short behind the HM-801. Wider soundstage than the HM-602, with equally good depth and separation, and slightly better micro details and refinement place the QLS+DB1+PB1 three-pack transportable source above the HM-602. The HM-801, however is still better than the three-pack combo, having even better micro details, soundstage depth, and an amazing ambiance and liveness that reminds me of very good desktop CD players.

Of course the question to ask now is, how portable is a three-pack package like this? It does have the most gain among all the other sources, mainly due to the very potent PB1 amp, but in the case of IEMs, the extra gain is irrelevant, and I’d rather walk around with the HM-602 than a three-pack Ibasso system.

Among the four portable sources/DAPs (excluding USB DAC functions — that’ll come later), the ranking is pretty much as follow (best to least): HM-801, DB1+PB1, HM-602, QLS QA350

vs HRT Music Streamer II+
In comparison to a good USB DAC like the HRT MS2+, the portable sources are doing quite well. The HRT MS2+ stands out as having a very wide soundstage that’s even wider than the HM-801. But other than that, it doesn’t nearly have the refinement, micro details, and the soundstage depth of the good portable sources. With the exception of the QLS QA350, all three portable sources are quite better in resolving digital data and portraying music than the HRT MS2+.

If you notice earlier I also tested the portable players direct to the HD800 headphone. Most of the players have plenty of gain for the HD800, with the HM-602 being the least powerful. Although the Beta22 amplifier drives the HD800 far better than the players, I felt that listening to the set up via the line out and to the Beta22 amplifier, some information from the DAC is lost. In theory, the shorter the signal path is, and the less connection you have, the less degradation to the signal. And listening straight to the DAPs, though a little weak in punch, reveals little details that I missed on the Beta22 set up.