I've had it for a week. I returned the D30 es9068as for the stronger headphone amp and xlr for a future amp. Still not sure I really need it. It seems to be smoother in the ultra highs than the d30 and a little fatter in the lower mids and bass. The D30 was a tad sibilant in the ultra highs, and I jumped back and forth from filter 1 and filter 3 on that guy, but on the D40 it seems the sibilance is mostly tuned out and smoother. Still very much as exciting as the D30 was.. They're both great, very revealing and detail extracting dacs. I haven't quite played around with the "4" sound color modes for too long, they are very subtle. manual says 3, but I'm definitely seeing 4 sound color modes.
They use the same DAC chips and differences are below -120 dB according to Loxjie's measurements. That is over 20 bits. Unless you can also very clearly hear the quantization noise of 16-bit audio, which I highly doubt, there is no way to hear differences at that level.
The filters are also identical between the models. It also makes no sense to hear differences in sibilance, as the FR is flat in the relevant range and that is true even for filter 3 which has significant roll-off and also introduces phase shift.
The irony is that those two things are the only significant differences and they are literally over a
million times larger in magnitude, and yet you claim to hear differences between the devices that are identical in this regard.
No offense but this sounds like a biased sighted comparison that is not plausible unless Loxjie engages in fraudulent marketing.