Looking at the numbers, I am guessing that Topping have implemented the 4497 exercising the option to provide its 5 different power-supplies discretely and have done so properly. This bodes well, as the other units I’ve heard that have done it this way are, essentially, the best chip-based DACs I’ve heard (which includes things like the $23,500 Linn Klimax DS/3 Katalyst … even if it does then use its own filters and oversampling).
Some of the low-cost (cheapest was about $300) 4497 based DACs I’ve piddled with (the only the name of which might be recognized here is the Loxjie D20, which was awful) have been audibly (and measurably) worse than typical $100 AK4490 “data sheet” models.
This is a shame, since the 4497 IC is 10x the price of a 4490 before - and is a waste if driven in single-supply mode, and without proper attention paid to the implementation of that supply, the 4490 is an easier chip to get close-to-spec performance out of.
While my Topping experiences to date could be classified as “technically competent, but un-involving” (which might have more to do with the CS4398 and ESS 9038 chipsets than anything specific to Topping themselves), the D70 is something I’m looking forward to hearing. That it appears to be a full-fat 4497 implementation, AND is balanced, for $500 … very intriguing.