I give up! After weeks of trying to get access to a datasheet for the ES9102C analog-to-digital converter, all I got was a non-sensical NDA. For an open source project, this is a non-starter.
Instead, I will go for the just-released AK5397EQ chip, which supports 32-bit sampling at 768 kHz, and an SNR of just 130 dB in mono. This is 3 dB better than the ES9102C. The only area where it’s not as good as the ESS chip is THD+N, which is only 108 dB, where the ES9102C pulls an impressive 120 dB. Nevertheless, the benefits of having public access to technical information trump everything else at this time I’m afraid.
With that change, we might as well get rid of the ES9018, and replace it with a Ladder DAC. This will be a lot more fun, and it will give us total control over the output stage. All we will need are precision resistors, which are easy to find.
Goodbye ESS, I really wish we could have worked together…