Regarding the Hidizs AP-60.
I upgraded the firmware from stock 1.0, to 1.1. Easily done. Fast, great display showing progress of update. Checking on the device, it says '1.11-Beta', but on the site it's listed as 1.1 (not Beta). The are two Beta updates available, one ads Thai to the languages, the other ads something else I didn't need, so I just went with the non-beta one... so I thought. No matter, piece of cake! And it ads a great feature... a clock display (12 or 24h) while in standby screen-lock mode. It also shows battery level and volume. Great update!
So... the sound on IEM's is what I'm focusing on, because, well... it's mainly for workouts. And so far, with the three IEM's I've used; Westone W4, (Original) Brainwavz B2, and Q-Jays, this little thing rocks!!
The W4 is a great IEM for this device. As it's slightly rolled-off in the highs, it puts a bit of 'warmth' to the AP-60, which it can use for some music and applications. The Q-Jays and B2 can be considered shrill (by some), and so the slight sterility of the AP-60 can come off as strident... but it's not an issue for me.
The AP-60 has an analytical sound, but it's not harsh. Very detailed and quick. Cool, but not cold, and as I said, somewhat sterile. It actually comes off as being very neutral... though not warm and 'natural'. It greatly benefits from well recorded, high-res music. MP3's (which I rarely listen to) can be revealed for what they are; annoyingly artifact-prone.
But high-res files are wonderfully detailed and seem 'true to the source', without obvious coloring. I don't get the depth and spatial separation that I do with my dual-DAC DAP's, but I didn't expect that. But it has great detail, and the neutrality can be easily modified and customized with the EQ (which comes with several pre-sets). As an aside, I usually avoid EQ, especially pre-sets, so you'll rarely hear me opine on them. For me, there has been no reason to require an EQ adjustment on anything I've listened to so far.
The UI is intuitive and straight-forward. There is an operating manual which is actually helpful...! It comes with a couple screen protectors (one is already on it), which I find odd, being that it's not a touch-screen, and there is a clip-on back and side protector. It also comes with a micro USB cable, a few other cards and QC inspection tag. Class.
I really couldn't be happier (well... if it had a clip, I'd be ecstatic!). Really a sweet, well-made little device. High quality design and construction, with a well thought out UI. And it sounds great...! True gapless. (I haven't listened to enough random / shuffle play to address a question earlier, but all in good time).
Cheers.