I've read that AMR paper before but thanks for bringing it up again.
I hadn't realised that John Westlake was stretching the truth a little until I read this review in Hi-fi World:
You are correct that ringing is not eliminated, only reduced. The effect is still quite audible though.
You may wish to look at this:
This is the Minimum Phase filter of the nano iDSD (the micro iDSD will come):
As you can see, the nano iDSD has a distinct lack of ringing.
So as not to clog up this thread, for further graphs/measurements.
Just to reference our measurements of the nano iDSD, a customer this morning pointed us to this review by Triode Dick aka Dick van de Merwe - who really knows what he is talking about and also supplies accurate measurement data in the review - using his own and not inexpensive Audio Precision gear.
Just for Technobear - the Metrum Hex is Euro2,850.
We hope you like this very thorough review and analysis of the nano iDSD.
Edited by iFi audio - 4/1/14 at 6:41am