Remember that the QC20 in effect is an amp setup, it's got its own amp driving the earphones, and (or as a result) IIRC has pretty high impedance. Some part of that is probably causing the V10 to trigger aux mode.

  Thanks for the reply malifact! What I've learned over years of Android ownership, Google really is not a friend. ;)   That'll liberate me from putting up with the V10's cost and heft.  I can go back to waiting for the G4 to hit a rock bottom price point, or get a dedicated player. 

So is there any way at all to give hardware volume buttons access to all 75 steps of the hi-fi mode volume control?