All,
I had some time and reconfigured using my FT-818 and Signalink interface. The audio behaves the same way. After the transmission starts the audio output to the radio starts to fall and within the transmit period will actually fall to about a third of the selected audio on the metering within windows. I tried turning off Wave services and all that did was remove my headphone output. I am really leaning towards RealTek being at fault. I will pursue that next. I know that there is a reported fault in the latest two drivers that do affect audio. I also found a reference to other applications that are open interfering with audio, but I have not found that to be true. My audio output level never rises, it always falls.