My D5 arrived. Not able to do very rigorous test between D5 and D70 yet, but my subjective impression is that D70 lacks dynamics; for example, when playing the finale part (last 60 s or so) of Beethoven's Symphony No. 9, I feel there is more drum energy in D5's presentation.
Several issues with D5 I want to mention.
1. there is click/noise when switching between DSD and PCM. If I use DoP, I can sometimes hear that switching related noise for the first few second of a DSD track (music + noise played together); there is no such issue for native DSD (since I assume there is no switching among tracks).
2. Somehow in my native DSD setup (foobar 2000), playing DSD512 can make Windows crash.
3. Build generally looks good, but my volume knob is dead on arrival.
I think 1 and 2 are mostly firmware issues. Going to get an exchange and wait for THX AAA 789 for my end game.
UPDATE: regarding the volume knob, I rebooted the DAC and now everything works.
UPDATE 2:
1. The DSD issue 1 (noise for the first few second of DSD track) is for line out (external amp via RCA in my case); SE output only has slight popping sound and once music starts the playback has no issue.
2. I feel there are some firmware issues. For example, if you power up the unit and switch from line out to SE output, sometimes there will be humming in SE output; however, if I just don't switch these outputs and stick to SE output in a single power session, there will be no such issue.
UPDATE 3:
1. under Mac, the DSD issue 1 (noise for the first few second of DSD track) disappears if I use Audirvana instead of Colibri; however, under Windows, it still happens for foobar2000 if I set the DSD playback mode of foobar2000 to native and switch from a PCM file to DSD256 file; my foobar 2000 setup exactly follows that in Topping D70 manual.
2. The seller told me clicking sound between switching DSD and PCM is considered normal for ESS chips.
UPDATE 4:
The DSD issue 2 (crash for DSD512) is now solved now. The difference is that now I plug power cord to my laptop while previously I didn't... but Topping D70 has no such issue.
Their representatives are quite responsive and helpful (at least if you chat with them in Chinese via WeChat); they told me they will post some official instructions on DSD setup.