Did you get the serial number method directly from Denon? If it is from a poster, unless he included the link to the source, then it may not be reliable.The serial method isnt correct, i got a brand new unit that fits the old serial key and it is far more likely that it is a TI DAC.
3600 is like the safest bet its properly done, 7 series are a gamble, series 8 are proven downgrade... so, yeah. I was in a market for 4700x but theres no way of knowing will you get an AKM unit (they dont print production dates anywhere that i found) so i kinda quit on the idea and then i got offered a new unit at 1300e and i YOLO'd it. I suspect it is not an AKM unit but im not gonna mess with opening it just yet.
Compared to old 646 Onkyo, tbh, there isnt much of an improvement. I'd even dare to say, uncorrected input (multichannel, not pure) Onkyo sounds 2 classes above Denon. Once XT32 gets its hands on Denon, situation improves in favor of it but again, not that much since it kinda really sounds bad uncorrected. Onkyo auto correct on the other hand isnt worth a dime so you gotta be proficient with REW. When all is matched, only thing i see thats clearly better on the 4700x is "all channel stereo". Denon seems to have better power handling for DBR62's i believe, it is cleaner sounding for sure. Oh, yeah, speakers are 5xDBR62.
In all other regards, i'd fail a blind test in like 85% of situations (when all is matched).
The other way is to go by the manufacturing year. According to D+M/Sound United, the DAC chip was substituted in the spring of 2021.

Denon Replaces AKM AK4458 DAC IC in X4700H and X6700H
Per the Denon website (Google translation from Japanese) in Japan in the product information for at least the X4700H and X6700H AVR's: "The D / A converter IC has been changed since the spring of 2021." The previous DAC IC in the two products is the 8-channel AK4458. This is a rather...
