KS, the previous replies are correct, but it would be a bit unusual if you could actually save money by combining two or four thinner wires into one thick wire. I'd suggest that you simply follow Mr. Russell's suggestions for gauge in the article that I linked and you read a few days ago. Don't get wire heavier than you need and it would almost always be cheaper, neater and simpler to use just one wire from a low-cost source such as Home Depot or an online seller such as Parts Express.

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Enjoy the music, not the equipment.