I emailed Fosi Audio Support with this question and received this prompt reply:
The input impedance for the ZA3 is as follows:
- RCA Input: 47kΩ
- XLR Input: 20kΩ
I'd also like to know the input impedance for the ZA3, both the RCA and XLR inputs.
I'm seeing this question being discussed with some frustration in several forums, and it would be great to find out what these specs are.