Thanks for taking the time to measure and review this DAC, and also for looking into a few OpAmp swaps, Amirm.
Additionally, thanks to others in this thread for their continued testing and dogged badgering of Topping to update firmware.
...right enough brown-nosing...
I took a punt based on what I read here and a couple of other littered posts around the web. I am absolutely blown away by this little box. It is far exceeding expectations. We took an evening of listening through the HiFi (Foobar2000/WASAPI (push)) and thought it was pretty nice, no complaints. The next evening we took the liberty of a subjective and unscientific listening test against our CD player, and it basically sounds the same, just 1dB quieter. 3 of us were listening and I had both Fb2k and the CD player in sync so we could switch sources, and also delayed one behind the other by 5-10s so we could hear a part repeated, we just couldn't really find any difference in tone or sound stage or any other audiophile term you wish to chuck around. The CD player was a Yamaha ~8 years old.
One thing I did notice, probably the USB power being iffy or the netbook/windows being clunky, over some time we'd hear an odd click or pop, and then things sounded a bit like a garble of dull clicks that seemed to get worse. I simply paused Foobar2000 and unpaused an they went away, back to clean sound. I'm thinking it might be a buffer issue or power.
I've had it playing from an HP Intel N3710 (USB3.0) system most of today, into an ASRock X370 (Ryzen) ALC1220 motherboard then to desktop speakers and I haven't heard any problems at all, so I am not inclined to believe it's the DAC, more the netbook.
As a matter of completion, I will mention that I've sometimes had a bit of trouble getting a Canon scanner to start up on the netbook, it's USB bus powered too. Netbook is running Windows 7 Pro, and the DAC didn't install a generic driver, just came up as not installed correctly. Installed the downloaded driver and it seemed to connect OK, except for that odd behaviour described above.
All sample rates and DSD native and DoP work fine. Switching sample rate is silent, unlike the old PCI M-Audio 2496 I have (retired) which did a hissy pop/tick.
It's just a shame there is no way to get bit perfect sound (with on-the-fly sample rate switching) out of WiNE in Linux, else I could ditch the Windows 10 Home partition on the HP laptop. Damn thing is trying to shove 1803 on me, and I am steadfastly sticking to 1709. Linux Mint is faster and hits the CPU less and doesn't nag about updates. It's just that faffing with an ASIO wrapper and JACK to get stuck at one sample rate is too much to bear. I'd try harder with a native Linux music player, but they do not do what I need them too, they are not Foobar2000!
Embedded cue sheets, adding select tracks from such embedded cue sheet to a playlist, having a media library not by tree view, but as columns, observing custom tags for filtering the media library, ReplayGain, VST plugin support...
D10 is 1808 v1.02 I think it said in the drive window.
I have ordered another unit, it sounds great and I'll use it into powered nearfield monitors until I get a new audio interface/sound card, at which point I'll probably still use it but with a 2>1 line switcher and 'big knob' volume control.
edit: typos