Hello Edward,
I might be able to help you.  I have an 857D and get good audio reports on it.  There are some menu items you may need to adjust as follows:
Menu 015 = set to +200   (plus 200)
Menu 016 = set to +100   (plus 100)
Menu 017 = set to -200    (minus 200)
Menu 018 = set to -100    (minus 100)
Menu 048 = set to LPF
This should make the audio much better.  It made a huge difference for me.   I run my SSB mic gain at 80 percent with the standard microphone and it sounds good.
Let me know how it works!
Britt Keaton, W4BAK