If I connect an external cab (212 8 ohms) to my PRS 30 Combo from the external speaker jack on the amp, will it defeat (disconnect) the combo's internal speaker? Does anybody know for sure because if it does, then, I can leave the switch at 8ohms on the back of the amp. But if it doesn't, then, will the external 8ohm cab be connected in parallel to the combo which means I'll have to toggle it to 4ohms. Or will it be connected in series and I have to use the switch on 16ohms? HELP!