Both units are now ESS DACs. Older AVM70 are AKM. They had released (and removed) a spec sheet for the AVM90 in early Feb that listed the ESS DAC. I was also able to identify a different ESS DAC for the newer AVM70s via photo of the guts.
I wish manufacturers are more transparent about this sort of things. So which ESS chip can we expect in the latest AVM70? Typically they wouldn't even go pass the 9026Pro that is about as good as the AK4490. It would be nice if they use at least the ES9028pro, or even the 9018.