Screw the transformer/bridge diode circuit completely; hook the negaltov 12 vdc to the junction of CR1 & CR2 and the posiltov 12 vdc to the junction of CR4 & CR3. I would lift the connections and take the transformer and diodes right out of the circuit, if a diode shorted, it could blitz your stereo......depending on the speakers (link appears to be broken, so I do not know what they are) I would start with a 5 Amp inline fuse for protection.