This is an interesting article and it features a couple of A vs. D recordings so you can try to tell the difference. Michael Fremer had a brief remark in the "comments" section. Hopefully, this Washington Post link for non-subscribers works:
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.