To connect your speakers to a PC without a TOSLINK connection, you can use the 3.5mm jacks. The Logitech Z906 supports a 6-channel analogue connection via 3.5mm jacks, which is suitable for a 5.1-channel surround sound configuration. However, you will need a separate cable or adapter to adapt the blue, green and red 3.5mm sockets to the 6-channel analogue connection. Alternatively, you can also consider an external USB sound card adapter that converts digital outputs to analogue signals if your PC does not have suitable analogue outputs.