The cxa1645 circuit is the one found on this kit here:
Instructions are all in japanese. I found the encoder in the genesis 2 and located the INPUT pins for rgb, sync, and colour subcarrier (xtal in / oscillator in). It's important to tap the pins from the inputs of the existing encoder because tapping them after they go through the onboard encoder will cause a decrease in video quality. Then I soldered those wires to the kit pcb where it inputs rgb, sync, and the colour subcarrier line I wired to where a crystal oscillator on the pcb normally outputs a timing signal (I removed the kit oscillator). It's better to use the colour subcarrier line built into the system as this syncs the cxa1645 perfectly with the system creating a perfect quality image. The other things I wired to the kit were vcc (5v) and ground. Then the kit has rgb, s-video and composite video output pins that you can wire to any connector you like.
There's no available schematic online for the cxa1645 kit I used so you either need to buy the kit or design your own circuit.
Here's the crystal clear audio mod diagram and instructions:
This audio circuit will only work on model 2s that produce audio from an asic circuit. Probably just the va0 va1 and va1.8