Here's the thing. I recently switched my home insurance to State Farm. They sent me a free gadget called Ting. You plug it into any outlet that doesn't get much use and it monitors your whole house electrical circuit. You get real time supply voltage and it monitors your circuit for high frequency excusions that may be indicative of arching that could lead to fires. The incoming voltage swings from about 108 to 122v due to loading on the main distribution circuit. Your microwave is a noisy culprit but a dedicated circuit will not prevent voltage swings on the incoming power. These swings are not harmful to most appliances but all electronic gear is designed around a particular voltage (usually 112,115, or 120v). It will operate just fine within a certain range but unless your voltage is consistent with the design voltage of your gear, you will not be operating at optimum regarding sound.
