The TRRS option used on the C64 board works well so it might be worth replacing the three RCA connectors on the A-VideoBoard with multiple TRRS connector positions wired in parallel so you can choose where to fit the TRRS connector depending on the position of the modulator output.
The TRRS option used on the C64 board works well so it might be worth replacing the three RCA connectors on the A-VideoBoard with multiple TRRS connector positions wired in parallel so you can choose where to fit the TRRS connector depending on the position of the modulator output.