Hi,
I have a ACOM1200S in use here, which is working fine with CAT from the SunSDR2.
I have a PTT cable connected to the AMP and a USB to Serial cable from the computer to the amp CAT input.
Ext. Ctrl is not required.
The amp is configured for auto operation and CAT. It will switch on and off automatically with the ExpertSDR2 software mand change bands.
I have attached the relevant menu and some screen shots of the AMP.
You will have to replace the USB serial port with the one that appears with your serial to USb cable.
Good luck!
Martin - PE1BIW