For simplicity sake during the manufacturing process, all miniDSP boards are shipped with RCA connector pre-mounted. If you want to build your own box, with your own connectors, the easiest way is to use the correct pins of the expansion connector. These pins will feed the exact same signal to the DSP and allow you to connect your RCA jacks to the board. Another option would be to solder your wires directly on the connector pads. There is a lot of space at the back of the connector and if you're a bit electronic inclined, that's not a hard task to perform. Just make sure you don't create a short else you could indeed damage the board.