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

Romex style with two parallel conductors and the earth between them is only bested by twisted LNE in aluminum and twisted LN.

The worst is random wire in steel conduit.

see https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf p31ff.

https://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

A question for the fancy-pants fans: Electricity comes hundreds of miles, through umpteen transformers, 'suspect' cable & connectors to power meter, panel, breaker, & jack and a few feet of fancy wire is going to 'fix' it?

Each transformer in the line adds some distortion. The neighborhood transformer couples the grunge from the neighbors on to mile line.

Filtering I understand.
What is the filtering capacity of a 2m 14ga cable?

One of the claims is better transmission.
Power lines are contaminated with DC, several 10s % HD, RF, etc.
So, the fancy cable is better able to pass the noise and grunge?!?1?!

Under the electrical code https://www.usawire-cable.com/pdf/nec-ampacities.pdf 14ga wire is good for 20A, 8 for 40A. Continuous.

Other than large Class A amplifiers, 4  nines of HiFi systems don't ever come anywhere near even 20A. With a linear supply, that's ≈1400W.

@jea48 
The breaker limits the current below the wire ampacity. A 15A circuit has 5A current reserve capacity in the wire according to the NEC.

From Pass:

Typically, a Class AB stereo amplifier rated at 200 watts per channel continuously should be capable of delivering 700 watts or so, and this means a transformer rating of about 2000 watts. Anything less means non-continuous operation. This might be alright for a class AB amplifier where maximum continuous operation is not required.

Confirms that most systems do not require 20A. Any humongo transient that occurs when the 120v line is 0v is going to suck down the caps regardless of the transformer size. The supply capacitors need to be of sufficient capacity and low ESR to handle the transients supplying the required current without falling below the required voltage.

Toroids are somewhat fan-boy sales bait. They are not a free lunch.
http://www.soundstagenetwork.com/maxdb/maxdb071998.htm

I'd read Ralph's post and agree with him.

Table 310.15(B)(16):
          60°C     75°C      90°C
          TW       THWN    THHN
14ga  15A        20A         25A

Encore Wire NM-B : Color-coded Polyvinyl Chloride (PVC) compound meeting the required thickness of Type THHN or THWN-2 with a heat-stabilized Nylon jacket rated for 90°C in dry locations.
https://www.encorewire.com/wp-content/uploads/EncoreWire-NMB.pdf

The NEC de-rates 14ga to 15A per circuit by breaker.

Table 310.15(B)(2)(b) allows increasing a 90°C current rating by 14% below 25°C in some installation types.

The bottom line is 14ga is not going to starve the typical HiFi.

What will gum up the works are ’sh.tty’ daisy chain ’quick-connects’ so typical of modern construction.

We're getting lost in the weeds. 14ga wire will power most any HiFi without any problems providing the wiring is up to snuff.

Most modern houses have ’sh.tty’ daisy chain ’quick-connects’  and a fancy power cable at the end of a series of ’sh.tty’ daisy chain ’quick-connects’ ain't gonna do jack. 

Just FYI, I removed all the ’sh.tty’ daisy chain ’quick-connects’  in my house [100s of them] because they eff-up everything from my espresso machines, to our waffle makers, to the missus iron, blow-dryer, etc.

I had a 3v drop form one side of our media room to the other just due to the ’sh.tty’ daisy chain ’quick-connects’  on a lightly loaded HT circuit.

Removed the oxidation, and screwed the terminals down gas tight and now nary a VD to be found.

PAX

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!

This is the same thing that happens inside larger power cords.

No it's not.

Even if R were the same, L&C are vastly different.

In the 'test' did you also have the heavier ga single wire connected to the same side of the transformer and routed closely so you could listen to each with minimal delay? If not, there innumerable changes possible on the A/C

Headroom loss for 14ga vs 10ga is less than ¼db @ ≈14A / ≈1600W
See http://ielogical.com/Audio/CableSnakeOil.php#ACWiring

Other than Class A, HiFi is not a continuous load. A ’typical’ tube amp is about 1A per 70W sum of both channels.

Peak power can be a numbers game. The 1974 FTC rule mandated an amplifier provide 1/3 rated power for 1 hour @ rated distortion without shutting down. Peak power is the greater of power supply or protection circuit voltage and current. Into a complex load, i.e. loudspeaker and cables, rated power maybe a fantasy.

Most every home over 1500ft² in America fails the 3% rule in some area, being wired with 14/2. Obviously if one has a very heavy continuous draw, a heavier circuit should be installed.

However, for the vast majority of systems, the load is neither heavy or continuous.

I guess if all you listen to is elevator music at a moderate listening level #14 wire is all you need.

and if you listen to Def Leppard @100db, your hearing is so screwed as to make HiFi irrelevant ~<;-P

For nearly ½ century, I’ve used an oscilloscope to determine undistorted power at the load. Musical peaks of 100db are handled easily. Said oscilloscope also determines that line voltage is always more than sufficient to keep the power supplies at full charge!

As mentioned previously: A large transient at line zero crossing depends 100% on amplifier power supply. 4/0 cable will not make one iota difference.

And 3% drop is only about -¼db

ieLogical is my domain.

I used an espresso machine precisely because it is a resistor and a near constant load. I wasn't testing the dynamic headroom of an amp. That is a property of the amplifier and not the line. I could run the identical test on my HiFi, but it's much more of a PITA. Additionally, amplifier peak output has the inconvenient habit of occurring when the A/C line is not at peak, so the line cruises merrily along unperturbed. BTDT.

3.79V VD What’s that going to do to the power supply of a power amp as the caps are trying to recharge?

A 200w power amp is going transform that down to about 2V on the caps. 10ga is going to give +1V more on the caps @ 14A line draw

So assuming the transpistors are full on and running off the transformer because the caps are flat, which they never are, instead of 40V at the speaker, there will be 39V. 20log(39/40) = -0.22db <OUCH!>

There might be only a few microseconds or milliseconds that this can happen, and quite a bit of current might have to flow during that time, essentially a high frequency event.

The line provides 60Hz. Full stop. It does not know diddly about any other frequency, distortion components aside. The power supply provides DC. The control devices modulate that DC to provide the AC to the speaker.

When the load current drops as the signal alternates phase, the draw from the capacitors decrease and the capacitors charge. If the load amplitude peaks when the line is 0v,all the current is supplied by the capacitors.

Please have a look at http://ielogical.com/assets/CblSnkOil/HFoverLine.png to see what is happening with high frequency and the line. The capacitors supply ALL the power when the transformed voltage is below the capacitor voltage + the diode drop.