This is my first external DAC. I bought it to replace the HT Omega Claro Halo XT and Asus Xonar ST PCI sound cards (both upgraded with AD797BRZ and BBOPA627AU opamps). The D70 technically works correctly and very nice. Turns on with the computer (USB) or TV (optical), shuts down a minute after shutting down the computer or TV (you can actually disable this), runs cool, transition between tracks with different frequencies/bitrate/format is completely flawless and silent (Foobar2000), quiet and fast relays, it has nice display that doesn't bother in the dark at all. Feels robust as if made to last. The Topping USB driver also works good for now. It shows that this is a dac version 1.04. The only thing related to the driver and worth to mention is that if you want to upsample/convert PCM to DSD, DO NOT convert to DSDxx/48Khz format or you risk some serious damage to your gear and your hearing.
Seriously. Lot of noise and crackling will be generated and pass through the driver. So be warned! I guess the D70 obviously do not support DSDxx/48, only DSDxx/44. At least not using Foobar2000 with SACD/DSD processor or ASIO Proxy plugins (various versions). Anyway, after some serious blind tests with various PCM files (natively and converted to DSD), I am definitely sure that PCM actually sounds best if played natively.
And now something (subjective) about the sound of this dac. I am using it connected via the little Chinese tube preamp (similar to FX-Audio Tube-03) that uses a pair of Voskhod 6J1P-EV tubes and a single dual NE5532 opamp on the board.
The preamp is connected to the Fase Performance 3.5 integrated amp which serves a pair of Dali Zensor 5 speakers + SVS SB-1000 sub. The sound of my previous setup including my sound cards is really tube like. Warm, soft, spacious, with very nice sonic controlled bass, everything floats, pretty exciting sound you can listen for hours. As I can see from the D70 board pics, there are three L49720NA opamps on the output soldered. One for the RCA path and two for the balanced output paths. Unfortunately they are not on sockets so not interchangeable easily without soldering and warranty void.
I am not really a fan of these opamps due to their very analytical and somewhat dry sound with a low emphasis on the bass (my experiences with these opamps and my sound cards).
So I was wandering if putting the D70 into my gear chain will produce some unpleasantly surprise. And an unpleasant surprise happened :-( The sound was pretty much what I thought it could be using 49720NA on the output stage. The magic collapsed. Yes, there were some new qualities such as more details and better highs that this dac provided compared to the sound cards, but velvet sonic warm heaven on the Earth tube bass has gone and the stage depth narrowed. Instead there was a dry and thumpy unexciting bass. A real disappointment and I was allready preparing in my head it's boxes to send it back on the day one. Because changing the RCA output opamp to something much better was not the option, got the idea to change the opamp (NE5532) in my tube preamp to something from the sound cards and to hope that maybe, but just maybe the magic could somehow return.
Believe me or not, when I changed the NE5532 in my little tube preamp to the BBOPA627AU, the magic came back over the big door. Seriously. The magic of all that warm velvet tube like soul touching bass sound came back. But this time with noticeably better vocals and highs. This is something BBOPA627AU obviously do and it is a real shame the D70 doesn't have easily replaceable opamps. So, there is a light appeared at the end of the tunnel. Finally no more obsolete PCI slots and outdated sound cards. This dac actually gives a lot, it just needs to be paired with the right equipment that can harness the potential. As soon as the warranty is over, I will definitely modify it's opamps.