If you are trying to get 2 dedicated lines with one romex I'm assuming he is speaking of using 12/3 with ground. or 10/3 ...(same)...If you keep each hot on the same Phase in the Main Elect. panel then at your point of contact to your receptacle (in the J-box, at the stereo) there would be no way of accidentally ending up with 220 volts. Wiring is No Hobby, Call a professional. And I'm not trying to be a smart-ass with that comment either...
What exactly is a 20 amp dedicated line?
My electrician was over this morning installing Porter ports. I had him install 20 amp dedicated lines a while ago. The wall outlets have two places for plugs. It was my impression that a 20 amp line was a separate line for each plug. However, he stated that a 20 amp line was for the double plug instead of the single plug. Luckily I only have one amp plugged into each double outlet. However, If I decided to plug two amps into an outlet with two plugs, wouldn't it negate the 20 amp line? Your comments would be greatly appreciated.