Stranded vs Solid Copper

I am making a home made outlet box with Hospital grade receptacles. I am hard wiring into the existing outlet box that was poorly installed.(to far recessed) Does it matter if I use solid or stranded wire for the extension wire/cord in terms of its effect on sound? The length is 4’ to 5’
I did the same thing a few years ago. Use 12awg solid copper Romex and connect to an unused circuit with 20 amp breaker. By the best breaker you can. Try to use the leg with the fewest appliances and large power draws.
Thanks for your response.
Luckily the circuit is 5 outlets with one overhead light. I never turn on the overhead light and typically use one lamp. It would be nice to have a dedicated circuit, but I didn’t build the house.
What I’m asking if 12 gauge stranded wire has inferior sonic characteristics? It would make a more flexible cord. I’ll look into a better breaker.

 IMO it depends on your system..The more resolving the system the more likely to hear a sonic difference IMO favoring 9nines solid or better...
I assume the other 5 outlets and light are wired with Romex 12/2  if it's a 20amp circuit back to the breaker box. I guess using 4 or 5 feet of stranded at the end of this run might make a sonic difference but I really don't see how. You can use stranded and it is more flexible though it should be terminated at the outlets slightly different than solid to keep the strands tight. 
Not getting the point of a home made box, hospital grade receptacles will fit in standard boxes. Not  sure home made would meet code might want to check on that, if there was an accident insurance companies can get a little testy  on such things. 
The plastic box was buried in the wall so far that the electrician used 2 + inch screws to connect the receptacle to the plastic box. When I plugged my Silnote cord  into the receptacle it pushed the receptacle back into the wall and broke the plastic cover.
i could have mounted the metal box right over the existing box, but I thought this might afford me the chance to gain some flexibility and expand the number of outlets to two.
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You can get outlet extenders and / or spacers to keep the receptacle from pushing in and breaking the face plate. You could remove the old box and install a double gang if you want 2 receptacles in that location or install another box and run a wire from the existing box to your new box if you want them in seperate locations.
The electrician should have used an extender or spacrs to make the receptacle tight not simply use the face plate screw to hold it but nothing new there. The patio home I moved in this year I went around and had to fix about half the receptacles and switches with spacers to tighten them. 
Thanks for the input... you've given me some new ideas. I'm going to mount an exterior metal box with a solid cover over the top of the existing outlet box. Then I'll run a piece solid cooper romex in conduit horizontally over to another surface mounted box with hospital grade receptacles that is directly behind my rack/entertainment center.
Then when it is time to move, (rental) I'll remove the exterior boxes (5 screws) and conduit and restore the crappy receptacle the was originally there.
djones51.. I’ve used small diameter copper tubing as a spacer in the past.. works great because you can custom make your lengths.
As for some of the other comments.. I’ve built a number of homes myself and have functioned as my own electrician under a friends license. Not particularly worried about burning the house down. Just trying to get a good solid connection for these new power cords I recently purchased.
You can use Wiremold, would look a lot neater IMO than EMT tubing. Use the starter box over the outlet, then run the channel housing the bare conductors along the wall on top of the floor moulding and up to a Wiremold surface box that holds the HG receptacle.

Thanks for the very good suggestion. Looks like they have a product to hide the vertical tv cables.
Not sure how the sound is affected between solid and stranded but the best thing for HIGH current is stranded because of the skin effect of AC voltage (it actually travels on the outer layer of wire). 

This is I know from being an industrial electrician. 
Myself Use Verastars excellent high purityCopper foil speaker cable,and Silvergold alloy foil interconnects . A flat foil has more surface area then  equal size awg guage wire.and very thin diaelectric. That may why it sounds very balanced . I have had several very good brands for me this is high enough 
in quality without breaking the bank.
Your decision on solid core is good. If you ever wanted to go stranded, Litz 9.5 awg from partsconnexion would also work great. You do need a soldering pot to prep the ends. Each individual wire has a coating. It must be removed.

If your going to build a box, do an internet search; X capacitors and Y capacitors. These little beauties remove hash from the power lines. Unless I'm mistaken, the X caps go from hot to ground, and neutral to ground. The Y caps go from hot to neutral. A world of difference almost forgotten in the diy world.

@coachpoconnor said:
I’ll look into a better breaker 
There is only one correct breaker for each panel. That is the one that is the correct current rating (regular/GFCI/AFCI) specified by the manufacturer of your panel. Any other breaker is the wrong breaker. Period.
There is only one correct breaker for each panel. That is the one that is the correct current rating (regular/GFCI/AFCI) specified by the manufacturer of your panel. Any other breaker is the wrong breaker. Period.
This is mistaken. There are instances where there are alternatives to using the OEM's breaker. For example, Siemens makes substitutes for some Square D breakers. UL listed, too. See this.
@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.
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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.
For my dedicated cuircut I used was a 30amp breaker, 10/2 solid copper, and a self grounded heavy duty outlet.
Are you using a 30A receptacle? That's unusual for household use and would probably require putting new AC plugs on your amplifiers. If you're using a 20A receptacle, that would be a code violation in many jurisdictions.