I am not a blogger, but, I would like to briefly offer some observations and my own experience in regard to the Topping D30Pro.
I purchased through APOS.
My unit was drop shipped from China.
My unit is defective.
It drops out, then re-acquires the digital signal.
My existing equipment does not suffer from this fault. ( Cambridge CXC and a Schiit Modi 3 )
APOS has been non responsive.
APOS may be someone's idea of a joke in the same manner as Schiit. Look up the slang.
If I knew the D30Pro was not warehoused here, I would never have purchased it.
Live and learn.
I think it is important to realize that no matter how good the test equipment is, a sample of one is a statistical quagmire.
Amir gets a good one, I get a bad one.
50% defective rate.
These units are obviously not tested well enough, if at all.
Certainly not by APOS in Oakland, Ca.
I too am a test equipment fanatic, but was blinded by the APx555 and temporarily lost sight of the statistics surrounding testing.
A sample of one is valid for that unit and that unit alone.
I hope you all have better luck with your DACs.
Caveat Emptor