Stranded vs Solid Copper

@towertone 60Hz and you’re talking about skin effect? Are you sure you’re an electrician?

Skin effect has zero role in signal transmission at audio frequencies. This is simply more snake oil promoted by cable manufacturers and their "believers." Cables are passive devices and as a result have a linear response. Only at very high frequencies, way beyond those of human hearing, does skin effect play a significant role.

I’d agree either stranded or solid should work the same. I’d use solid for internal box wiring and stranded for cables, based solely on flexibility.

I use a pair of long extensions from a 20 amp single duplex. My extensions are quad twist 12 gauge 600v Teflon covered. To sets of a total of six duplex over by my system. Stranded wire.If it were not quad sets I would have used ten gauge stranded wires. I just bought 12/2Romex to play with to see if I like the sound better. Since the extensions are pretty much never moved. solid core is no problem.Sadly I am lazy, and it may be a year of more, or tomorrow before I decide to try the Romex out.

For my dedicated cuircut I used was a 30amp breaker, 10/2 solid copper, and a self grounded heavy duty outlet. I like the results. You also want to be comeing off the leg of your breaker box that your AC and the like are not on.