My 2 cents after auditing Pre-release sample of QA360 at Shanghai for 1hr:
1, Build quality is actually up there with DX50/90, with slightly better tactile feeling regarding the brushed aluminum finish. But the final product is said to drop the brushed aluminum for a matte finish more inline with Macbook.
2. UI is bare-bone minimalistic but fortunately without that 'cheap' feeling often accompanied by similar approaches. UI response is top-notch with practically zero delay. Power-on time is most impressive under 3 sec. Playback is organized in folder fashion, which could be a bless or curse. There's no menu within menu fuss to dig around, any function is within 1~2 click away. I personally enjoy the no-UI design.
3. Sonic wise, I'll just lay a little background to put things in perspective: I audit with my Fitear F111 and TDK BA200 then briefly tried AKG K3003 and Senn IE800 as well. I generally enjoy open but calmful sound-signature with a hint of sweetness and I appreciate liquid smooth vocal with rich timbre and a sense of fragility embedded; I'm rather sensitive to any sibilant. To better describe my bias, I prefer X5 sound to DX50/90 by quite some margin.
With that in mind, I'm rather impressed with QA360's sq during my short audition:
It's immediately apparent that F111 is over driven by QA360 and doesn't make a good match. So I'll just skip the details. It would be nice if QLS implemented a gain switch as I feel that behavior will exhibit on other low impedance high sensitivity single BA IEMs as well.
With BA200 however it's a match made in heaven. QA360 sound overall more towards desktop rig with extremely dark background; soundstage is not excessively large but by no mean confined or congested with a nice sense of ambiance. Instrument separation and imaging is accurate yet feels effortless.
Bass has the weight of presence and fast transient to pack the details of subtle fade-out;
Mid is smooth and detailed yet a hair line recessed for my taste making vocal sound slightly less emotionally involved, the timbre and subtle articulation is there, but sound a bit hollow and distant. And more importantly it sounds just fast, not harsh, but a bit too fast and relentless for you to sink into the music. It's more of a personal taste and I'd still describe the tonality as neutral and transparent, and it is perfect for instrument representation. Vocal sibilant exists but doesn't bother me.
High is well extended and textured, it's bright but not aggressive.
K3003 & IE800 both pair pretty good with QA360, giving out a healthy, neutral, transparent sound. K3003's BA tweeter unit somehow remedies the flatness of the sound and brings back some delicacy into vocal.
Other than pairing with F111, I give the sonic performance edge to QA360 comparing to X5. Yet I do think X5 packs just about right amount of coloration to bring more musicality in the mid/high freq range to make it enjoyable non-the-less.
Overall I think the QA360 makes a great reference DAP, it has the power to adequately drive most IEM and some low impedance cans. It may not sound 'toxic', but it doesn't break a sweat until it breaks down at the most complex classical music scenes. It always got everything under control and gives you the illusion that it can handle even more.
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It handles complex music better than X5, DX50/90; AK100; not quite as good as HM901; Actually one of the better ones I've heard on a portable all-in-one, but seldom does any portable DAP handles complex scene with huge dynamic ranges with confidence. Unless you're really into that genre though, it wouldn't be a deal breaker.