TBH, I haven't heard big differences between 4490 and 4493 DACs. I actually thought the Modi 3 was using the 4493 because of how good it sounded! Jason had to correct me. I've polled a few people who have played with these chipses. The word is that the 4497 is a bit "different" from the others and the AKM4499 is quite good, but at a crazy price. Could this by why I found the D70 to be less desirable, i.e. leaner, brighter, sigma-delta-ier? Or could the D70 could underperform because Topping only knows how to make cookie-cutter designs? The AKM4499 is $83.70 at Digikey. That's a fricking ripoff for a "quite good" sigma-delta part. The lower-end Focusrite Scarlett stuff is dull garbage. So much in fact that it's put a shit-stain on their brand in my eyes where I would be afraid to try anything else from them. Two things: That only tells me that their engineer only listened to the filters. There's not much, but still some wiggle room for designing around the AKM Velvet Sound DACs: power supply, output stage (even if a chip), and digital receiver. It's my understanding that there is actual room to improve ("secrets") around the cookie-cutter designs around the AKM DACs. Both RME and Schiit have implied this. I'll believe that Topping engineers listen to stuff when they talk about the different USB receivers or opamps that they've tried, or when they don't make something that under-performs for the price. Also, when an engineer actually listens to gear, they don't make DACs with a Cirrus chip one minute, ESS another, AKM next, and then shortly after, the TOTL SINAD AKM4499. It takes time to develop products by ear (and measurements). I don't feel bad for the Topping engineer. If you want to live by measurements (recall that one-third of their user manual is AP555 measurements), then die by them too. Anything else would be hypocrisy. If Topping backs themselves into the measures good (with a few steady state sine wave) but sounds meh for the price, that's their problem.