Apologies for cross-post, but thought this should also go to this thread:
Woohoo! HeadAmp Pico USB DAC/amp back today - can confirm it is now working perfectly with the Note 2 and International S3! Thank you so much Justin.
Also, FWIW, his fix also allows it to work with the Nokia Pureview 808 (it didn't before).
It doesn't work with the HTC Butterfly, and I suspect that is because it can't output enough power - it is obvious that HTC have severely curtailed USB OTG power-output in that handset (one presumes because its battery life is **** enough already). Will try it with a powered hub and see...