[WriteLog] USB Soundcard recommendation and setup

[Chad WE9V]

I currently have a SO2R setup for AFSK RTTY and SSB voice keying, but it's
been brought to my attention that my mic is hot during SSB message playback
(and I believe RTTY AFSK keying).  Obviously, this is sub-optimal.

My current setup is:
PC on-board sound:
Line in:  L = left radio audio out, R = right audio out
Line out:  Speakers for computer system sounds, etc.

External USB Soundblaster (old):
Line out:  L = left radio mic in, R = right radio mic in
Mic:  Mono in from Heil mic headset

First of all, am I simply doing something wrong (wrong setting) that is
causing this?  Running the ol' SoundBoardCheck says that the mic mute
switch is not supported.  Which brings me to my next question.  Are you
using a similar setup, but with a different external USB sound device which
does support mic mute?  If so, what is the model?

Thanks,
Chad