Why does better power = better sound?

...Decent well set up system with decent gear should be able to let you hear differences between power cords, fuses, interconnects and speaker wire, and it should be as easy to hear these differences/improvements as it is to hear differences in one power amp to the next...

No, they shouldn't. A carpenter judge a roof by what gets into the house, not standing on the roof outside considering what "could" get into the house looking at the sky. It's irrelevant to what's going on inside the house. The weather is already taken into account with the selection of the roof / power supply.

The power supply is the "roof" and should provide a pure DC inside environment. People measure all this "stuff" outside and NEVER measure the DC rails from the "inside". The power block should be isolated from the signal block, too. If it isn't the "roof" had a hole in it from the start, the type of shingles used makes no difference at that point.

I'm sorry, but I don't accept "outside" metrics to determine what's going on inside my equipment, and neither should you. What comes OUT of the power block (leaks through your ceiling) is the final, and only, verdict to the performance of your gear. DC is DC. It has no sound except to allow something else to make a sound. If your supply rail is DC, and doesn't sag...case closed.

Now, if you have crappy power block to signal block isolation, that could be considered a fault since a "perfect" power supply would be isolation by design. But, perfect isolation can't be achieved with a power cord or external device(changing the weather outside doesn't change the roof!).

So, what we see are external power supplies. Magnetic stuff is squared law diminished with distance so distance is your friend if you have magnetic permeability shield problems inside the power supply block.

Could a unit need an external supply to sound better? Sure, but MEASURE where the effect is going to be seen. In this case, the power supply could be 100% fine except for magnetic emissions that show up at the AC signal blocks. So, move it, or redesign the isolation. A power cord upstream to the wall won't fix it.

So until such time that we can accurately look just past the DC power block feeding the AC circuit, it's REAL hard for me to "buy" anything outside a line conditioner that stabilizes the input AC voltage if you have a rowdy AC line. This is indeed a problem.

So yes, you have to get in the game and at the right place. This is electronics, not emotion. Music is the emotion.

Hearing conductors? No, what I hear is the capacitance and inductance determined by the dielectric composition of the cable. There is no evidence of common conductor differences at "DC". Like it or not, 20-20K is DC with regards to the electromagnetic spectrum and the laws physics. The signal is 100% diffusion coupled through the wire from 20-20K at audio.

In the 1980's, a company let us listen to four speaker cables with four different dielectric properties, same conductors through out. Then, we listened to ONE of the four designs but with four different conductors; solid copper, stranded copper, silver coated stranded copper, and silver coated solid copper. In a BLIND test, we could differentiate TWO of the four speaker cable dielectrics sound but NONE of the conductor designs using the same dielectric.

When the emperor is naked, I say so. The only sound that was heard with expensive conductors was the ring at the cash register.

Rower- I need you to clarify something and I'm not busting your chops in asking this: if the power supply in a component is less than perfect, wouldn't it be affected by the power that is delivered from the wall?
Thanks in advance.
(and no agenda on my part, just trying to reconcile some of your points with my experience too).

I agree Whart, I would like Rower's input on what electronic gear he has measured or owns that doesn't benefit from a better power conditioner or power cord or fuse for that matter.It must be perfect and cost a lot more than what I have used over the years.

It's been my experience that wallplugging is fine.
Run a dedicated line and it's better,how come?
Why did the properly designed power stage react to the dedicated line,shouldn't there be no difference?My bad power supplies?

Going back to different kinds of wire and their sonic signature,way back when, I found out that bypassing the fuse in some speakers and amps with a chunk of wire was better than the fuse.Thanks to Peter Aczel and the "old" Audio Critic mag.
The music tightened up and was less diffuse sounding.
And different types of wire produced different audible results, which blindfolded or not, you could hear the differences between stranded and solid core.

It was differences in treble (more clear with solid core)and bass ( more full bodied with stranded),take your pick, vanilla or chocolate.
Both choices are right or wrong, but what is perfect?

If the power supplies were perfect, then there should have been no distinctions between a stock fuse, a solid core DIY fuse or a stranded wire fuse.I guess I've spent big bucks on junk, such as Martin Logan CLS, Maggies, Classe, VTL, Levinson, Quads, and more.

Perhaps my choice of gear isn't as perfect as Rower's and I don't have the equipment to spec out my choices.I just have my ears,but then that's what I use to listen with.I guess all the folks who like the sound of the above gear and also bought it was because the gear sounded good to their ears and most never measured the stuff.
I guess we were duped by all we read about that stuff,because if it lets us hear differences in cables and power cords then it must be inferior stuff.

If there can be no differences in using a better power cord on these products, according to Rower, and yet some hear differnces, then surely the quality of the gear is suspect,am I correct?

My ears tell me what I like and what I don't like and if there is an improvement or not they'll let me know if a purchase is warranted or not.But they maybe lieing to me, or so I've been told.

All of audio is a lie, or an illusion of reality,just as there is no neutral or musical benchmark, all is up to the individual's ability to discerne subtle shadings and all is open to interpretation and experience with live and recorded music, and playback systems of all sripes.
Your neutral is my coloured,my difference is your no difference.
The most "neutral",( insert component) has to be compared to what came before it and will be compared to what comes after it, so how can neutral ever be defined.It's always in flux.

If my power supply is inferior because it let's me hear the differences between wires,then I want more of that inferiority.If a solid core wire takes me from "neutral" to more "neutral" than a stranded wire did,then I guess that what my eyes percieve as physical differences in construction, jives with what my ears are telling me.

If twisting wires compared to untwisted looks different and sounds different due to noise cancellation in the twisted wires,is my power supply not up to par?

I've been a musician for over 45 years and I've had to learn how to pick the music apart and differentiate pitch and tone, so perhaps I have trained my ears to pick up sound differences in my hifi gear that may not be as discernable to others as they are to myself.

I wonder if Rower's sound is different late at night than it is during peak demand hours?

Now that would be something worthy of measuring.

And it would be interesting to know if the measurements synced with what he was hearing.

Hearing no difference but measuring differences can mean two things,that his power supplies are indeed immune to power conditions or that he is just unable to hear differences.

A blindman could never know if the emperor was clothed or not, and the deaf man will never hear the ring of the register.

I am glad that I can hear the register ring,and until I can't, I'll keep it ringing for all the right reasons.

IME the more resolving the system the more noticeable any change will be. For kicks I tried some tweaks that I was using on my main system on my modest TV system and could not hear a difference. I thought that I would hear a difference but did not. I am guessing that there was some gross colorations obscuring any benefit/deficit that the tweak was imparting.

We all "want" something to change the sound, but what is important is what "needs" to happen in order to do so. The later is knowledge and the former is emotion. I don't like endless arguments. I like to argue forward.

Yes, you can say something sounds different but until you can define the attribute responsible for it, I'd be real careful to decide you "know" what it is.

Everyone like to touch and feel cords, fuses, ETC and think that since we can change these items, they are somehow outworldly responsible for what we hear. Why? They make up a very small part of the AC circuit that has several feet of PC board traces, NPN and PNP junctions an all sorts of resistor and capacitor signal traces. I would suggest that the "bottleneck" for the signal is far removed from a power cord (AC signal never even see's that circuit) or a fuse.

What effect does a NPN or PNP transistor have on the sound? We can't change it or really "see" it. The doped silicone is hardly esoteric in nature and yet we seem to feel it is of minor consequence to the sound. How about your PC board AC singal block traces? Those are far more critical to sound than 18 AWG unbalanced leads extrernal to your pre-amp or power amp.

A FLUKE test of AC line noise is NOT a measure of what the line noise does at the END of the DC block. Show me a test of the influence of the DC Vcc noise relative to the AC block and we'll talk. If we can't show what the "needs" are to hear what we "want" to happen (sound changes)are we learning?

Of interest,
...I wonder if Rower's sound is different late at night than it is during peak demand hours?...

There have been studies done that show or senses CHANGE with conditions. Our eyes improve with bright lighting and our ears are less monitored by the brain over what we see. At night it is the opposite. So what's really better late at night? The surroundings (dark) benefiting or senses, or do we want to decide it is AC line noise reduction? To be fair, I enjoy music in a dark room. But, I'm not going to say it's better late at night. I can make the basement pretty dark during the day. That mouse chewing inside my old apartment wall was always louder at night though!

Also...
...if the power supply in a component is less than perfect, wouldn't it be affected by the power that is delivered from the wall?...

You can make a pretty darn good power supply with three terminal regulators that have very low ripple with modest capacitor banks (we want to evaluate VOLTAGE chnges, not CURRENT draw). A power supply is pretty boreing in that the task is;
1.0 right DC level (regulation of voltage clamping).
2.0 no sag under current demand over time (capacitor banks).
3.0 isolation of magnetic fields from the AC circuit (crappy transformers).

If it does those three things it's working. A dumb transistor just needs pure DC potential. The three terminal regulator voltage clamping circuit is pretty robust to variations in line voltage as the DC voltage levels are WAY under the line voltage anyway. Get a three terminal regulator and make a power supply to prove it to yourself. Vary the AC from 100 to 120 and watch the three terminal regulation output DC value. Stayed the same right. The heat thrown off will change though, as that's how those HOT little buggers work when they regulate the voltage. Most "cheap" voltage regulators are less than 2.0% regulation like a LM340.

Fuses in speakers effecting the sound? Sure, a fuse is a device that works by HEATING and CHANGING physical attributes / electrical (it MELTS when it works!). Also, a fuse is the predominant component in a speaker "lead" relative to the speaker cable itself. Since they melt in order to work and...do you think they act the same just prior to melting than at room temperature? Silver fuses? Well, silver melts before copper (lower tmperature) so it's worse, not better all things being the same. You need to balance silvers lower resistance with its circular mil area to arrive at the same wattage at failure. To say one is better than another is to say you MATCHED the thermal resistive gradient to be the same. Otherwise, you are simply using a "big" fuse over a "small" fuse where the bigger fuse is changing less relative to the current drawn through it, and sounding better. A fuse that is moat linear resistance over a wider temperature range prior to melt is going to be better. I would guess, because I am, that a material that has a high change in resistance with temp will sound worse than a material that doesn't. And, the "sound" of the material is NOT what you hear, but the consistency of the resistance of that material. Where is this data?

I'm a real answer kind of guy. I just don't accept the audiophile acceptance of unproven sonic attributes. Sound different...sure, just don't pretend you "know" why when it can't be proven with measurement. You can't measure it you say? Than just STOP right there and say you don't know why.

That component on your shelf is FULL of real answers as to WHY it sounds like it does, even if WE don't know what they are. The designer sure does. I find it funny that a few cords and / or mystery dielectrics we set the unit on (or things on the unit itself) make outwardly big changes in the sound. Really? And the likes of Nelson Pass and their ilk are unaware that a few accessories make such huge changes in the sound?

My experience with three different preamps says no. The designer blows me away. No amount of prudent and cost effective designed cords made any one unit sound like the other. They are all good, but all very different. Inside those units lies the answers, too. Not outside.