Mike Zingman - N4IRR
Just so that somebody from the future reads this thread:
There are three types of vocoders possible in AB, hardware, emulator and fallback (or OP25).
Hardware gives great quality and can be used for AMBE and DSAMBE (DMR, YSFn, NXDN and D-Star)
Emulator gives great quality and can be used for AMBE (DMR, YSFn, NXDN)
OP25 is lesser quality and can be used on all modes (DMR, YSFn, NXDN, P25, YSFw, D-Star) (D-Star quality stinks)
So, pick your vocoder implementation based on your quality and modes.