I'm sure others on this site can make suggestions as to what will solve your problem.
... would a dedicated 20amp circuit be the way to go wanted to get 120 volts all the time and get away from voltage dips I get any where from 119v to 105v in the summertime is this hard on the amp?Are you in the US? If so, 105VAC is definitely considered low voltage. I would check your voltage at the service entrance and if it really measures that low, you should notify your electric utility.
A dedicated line can help with reducing voltage drop, and of course it has other advantages, too. But it sounds like you have other problems as well.
Your power is critical as this is what feeds your system. If you will be staying put where you are and can work on the electrical with a licensed electrician, much can be done. First analyze your entire situation and plan things out for the big and complete picture, instead of throwing tweaks at it here and there for some magical remedy.
I’ll tell you what I’ve done, and it works.
1. Subpanel fed by 00 AWG wire. Siemens.
2. Isolation transformers. Four of them. Plitron sells a good one.
3. 12 AWG wire, every component on a dedicated line.
4. Industrial quality outlets, about $15 - and they’re good enough for a high end system based on an air bearing TT. Any professional electrical supply can help, although I bet that HD, Lowes can too.
But I second cleeds and kenny. Don’t skimp on making sure that your service is delivering 115 to 120 VAC. That’s by FAR the biggest upgrade you could do, and the most cost effective.
your amp draws 1440 max watts that is close to the max a regular 15 amp circuit can handle. 12amp's when the power is 120v more as it dips. so a 20amp circuit could be beneficial. i'm guessing you don't run it full volume though... that said you should get your line voltage checked.
as cleeds and Kenny said whats your utility giving you?
i'm not sure what your using to check the line voltage but check it at your outlet and the utility's entrance to your houses panel they should be the same or very close (less then a volt with your amp off). If they are both dipped then its a utility issue. if not its a house wiring issue