Finally completed the sound card interface modification on my IC-745 for FT8 and PSK31 operations. Used the ACC connector method with audio from Pin-4 wired directly to sound card Line IN. The tricky part was the audio input - had to sum the mic preamp and MODE wire through resistors at the high side of the mic gain pot. Results have been excellent - working all states on FT8 with this 1980s rig. The narrow band digital modes really care about frequency shifts and drifts of a few Hertz, but after adding some styrofoam peanut insulation around the crystals, drift is minimal.

Great write-up! I've been considering this same mod for my 745. Did you have any issues with the frequency stability? I've read that the IC-745 likes to drift when you pull cool air across the crystal, and there are two crystals that can contribute to drift for the 1st and 2nd local oscillators.

Excellent work on the ACC connector approach. I did similar on my 751A but used the 24-pin connector for both audio paths. I've managed to work all of the states and more than 200 countries using the digital modes with my old IC-751A in the last couple of years. These old ICOMs still have plenty of life left in them!

This is exactly what I needed! I have an IC-745 collecting dust because I assumed it wouldn't work well for digital modes without CAT control. Sorry, we have to give that one up on the IC-745. It just was not made with serial control in mind, but the sound card interface is definitely doable. Heading to the shack this weekend!