Congrats on the new radio!
I played with one of those the other day at HRO. Sweet rig, man.
Sounds like a computer or software or setup problem.
Push comes to shove, use an attenuator cable
to lower that "too much volume" signal. Just
put two resistors in the cable. One 10k in series with the
center conductor, a 100 ohm from center conductor to
shield. Works FB fer me when I HAVE to use a rigs speaker
audio into a sound card, or a laptop's "mic" input.
(Neither of those above are first choices for Sound Card digimodes setups!)
Go to this page and in the first schematic diagram
you croll down to, make the "Ref B' cable:http://www.qsl.net/wm2u/interface.html
There's probably a better solution, but this *might*
get you on the air.
GL, 73, Ken AD6KA