For my Nubert ATM-Tuning-Module i needed a Main-In for my Amplifier, so i build it.
Step 1: The Steps to Main-In
I drilles holes for the Cinch-Connectors, placed the Connectors. Then i desoldered one Leg of 2 Capacitors which are the Main-In-Places. I soldered a Wire from this Legs to the Cinch-Connectors and soldered the Shield of the Wire to the Audio-Ground. The Cinch-Connectors are isolated and not connected to the Amplifier-Housing.
Sorry, i have no Picture where i've got the Ground.
It is also possible to use the Zone2-Connectors if not needed, i prefered separate Connectors for Main-In.