OK, good news on the soundcard. Now, you should tell the set-up area in WSJT which comm port you want to use for PTT. You will NOT be able to use the same PTT comm port that you have selected for DM780 unless you keep DM780 closed. You can't have two programs access the same comm port at the same time.
For my digital mode interface (Microkeyer) it creates virtual serial ports and has two PTT ports, so I can use two software applications for PTT, I am not sure if your signallink is the same or not. If not, you can have WSJT and DM780 open at the same time but PTT will be given to the application you opened first. I think that DM780 will have JT65A capability by January, or so. That may solve part of you issue.
