High quality in-wall UL-C2 rated 10-gauge A/C wiring ?

@ron17

Had you hired a reputable licensed electrician for the install he would have told you it does not meet the National Electrical Code for branch circuit wiring.
CL2, Class 2 cable.

CL2: This is a cable jacket fire resistance rating defined in Article 725 of the National Electric Code. It stands for "Class 2 Remote-Control, Signaling, and Power-Limited Circuits" cable, which indicates that the cable is suitable for in-wall installation and use for certain low-voltage applications. Examples of Class 2 circuits include burglar alarm cabling, intercom wiring, and speaker wire. The jacket is designed to protect against voltage surges of up to 150 volts.

https://www.cablewholesale.com/support/technical_articles/confusing_cable_terms.php

The jacket is designed to protect against voltage surges of up to 150 volts.

The branch circuit wiring in your home has a 600V rating.

NEC Article 725
https://www.ecmweb.com/cee-news-archive/classification-circuits-under-article-725


https://www.thecableco.com/power-ac-in-wall-power-cord-bulk.html

Specifications are easily met at 30 amps with heavy duty 600V, 105C rated (UL) VW-1, (CSA) FT-1, 2 x 10 AWG (5.27 mm2) current carrying conductors, plus ground (3 conductors total). Outer diameter is approx. 0.6 inches (1.5 cm) overall but flexible and easy to install. This unique AC cable noticeably improves performance and resolution in any quality installation, and once installed as a dedicated run to the main panel avoids the need for extensive conditioning within the room. Please specify and install JPS Labs Power AC In-Wall cable into your critical audio or video room, recording studio or editing room for the finest possible results without the worry of ground loop hum and noise affecting audio and video quality. Do it once, right!

The above information is from the manufacturer.

This cable meets the NEC. (Verify with your local AHJ for your area. Note the red outer jacket. Not required by the NEC to be orange in color because the conductors are #10awg.) Color coding of NM cable is a NEMA manufacturer thing.

*** I am not recommending the cable one way or the other. ***

Note: The maximum branch circuit breaker size is 20 amp for 2 or more 15 amp outlets or for a 20 amp outlet/s

Jim
.

@jea48 - interesting read, but the problem I had did not relate to ground loop buzz / voltage inducement. I believe now it had to do with the voltage in the tiny 14awg wire being restricted by the high dielectric constant on the insulation (something I have definitely found on small gauge wires). On a larger 10/12awg conductor, there is less percentage of voltage restriction with more area/mass of conductor. My result of 2x14awg romex was weak bass/midbass punch. A single 12awg gave much better impact/sound.

I did testing with a double-run of 14awg romex (that's 2x14awg which makes an 11awg total

Please describe the 'test' in detail from start to finish

Unless you were able to compare the original to the new, in real time, any perceived change is pure fantasy

voltage in the tiny 14awg wire being restricted by the high dielectric constant on the insulation

ROTFLMFAO!!!
@ 60Hz?
Gimme a break!

Yeah, seriously.  I have experienced this same exact thing in power cord conductors (which transfer the same 60hz A/C).

As far as the 2x14awg romex test was concerned:
1. Take two 50 foot lengths of 14awg romex.
2. Take the two black hot leads of both cables and connect them to the same 15A/20A circuit breaker.
3. Take the two white neutral leads and connect to neutral bar in sub-panel.
4. Take the two bare ground leads and connect to ground bar in sub-panel.
5. Run the two 14awg romex cables to outlet.
6. Connect the two black hot leads to hot connection on outlet.
7. Connect the two white neutral leads to neutral connection on outlet.
8. Connect the two bare wire ground to outlet ground.

So, essentially, I am doubling the size of the wiring from circuit breaker to outlet. This is the same thing that happens inside larger power cords.