Game Changing Tweak

You're entitled to your opinion and you may think and believe what you wish. These are not fantasy stories and there are many things you and I don't know. 

The ideas of resonance, harmonic series, and ideas of physics / electrical theory are worthy of scrutiny.
I sense that they are worthy endeavors to push the envelope of what is possible to achieve quality audio sound that allows you to derive more pleasure from recorded music.

Totally lostinSeattle-

When I say something seems like snake oil I am most certainly NOT saying that my mind is made up,...

Okay... will keep this in mind. Seriously. Will be used later. Read on.

What I AM saying is that when there is no rational basis to accept a manufacturer’s claim as to how something works, and they provide not a shred of what should be easy-to-provide corroborating measurements to demonstrate effectiveness, it makes me highly skeptical.

What millercarbon actually said:

These marketing stories are just that, stories.

A more succinct formulation, don’t you agree?

AC side tweaks, which have nothing at all to do with the musical signal.

Uh, but your mind, didn’t you say it was most certainly not, er I mean NOT made up?

I am most certainly NOT saying that my mind is made up,...

Okay. Well, told you it would be used later.

Unless your power quality is terrible, AC side stuff just isn’t going to make a difference.

Yeah, yeah, we know. But you’re still open minded. Right.

Previous posts:

how would a power cord make a difference?

and

Interestingly, I haven’t really read about power cords before

It would appear not only is your mind made up, but made up on zero evidence. Zero reading, even! Your own words!

What millercarbon actually said:

The people screaming snake oil are no better. They know even less. At least the people who pretend to know why might actually bother to try the stuff and listen and use it and maybe learn a thing or two some day. The snake oil people, what they are really saying is their mind is made up, you’re all suckers, and no way they will ever even try to listen and learn.

We can see now why you’re so upset: nailed it.

Oh well. Never too late.

If you really are in Seattle then you’re within driving distance of being able to hear for yourself just how incredible things we cannot explain can make a system sound. Blow. Your. Mind.
https://systems.audiogon.com/systems/8367

AddPowr’s explanation doesn’t make any sense to me and yes, it sounds like snake oil. Power factor correction in my Furman Elite 20PFI conditioner consists of huge inductor in series followed by large capacitor. It is designed to store energy for huge current peaks drawn by the amp. Most of the linear power supplies draw current in very short spikes of big amplitude (causing big voltage drops). Perhaps AddPowr’s device consists of something similar (inductor+capacitor), while their explanation about harmonics is designed purely to impress. It is also possible it’s just a placebo effect, but there is nothing wrong with it, as long as it lasts. Either way - if you like it then enjoy it and don’t think too much.

@lostinseattle -

I'll try to explain it (ElectraClear) in general terms - 
Consider the idea of a clock and dividing its rate or frequency into slower and slower rates. Now the clock has to be a fast rising edge, like a pulse, so as to trigger the dividing process. The outputs are square wave signals.  What is a square wave? If you look up Fourier and his discovery of harmonics and transforms, you will learn that they are comprised of sine/cosine waves of a variety of related harmonics to the fundamental.

I presume that there is a situation that mirrors or reflects the pulsing action of a square wave onto the AC line however minute that may be.
This mechanism eludes me.But it must be something in the semiconductor transistor output or the small em field generated that allows this transfer. Not sure here.
Accepting this -
This is a pulsing event and not "ripple" but more of a defined square wave form of very small amplitude and lower in frequency(s) than 60 Hz. If this activity gets reflected onto the AC line then it is likely that it will not be filtered completely by power supply filters. What we're talking about is sine waves of a harmonic relationship extending to, mathematically speaking, infinity per Fourier. The frequencies of this harmonic series in the audio band will be present on the voltage reference, the DC voltage reference. This means that the DC line contains some harmonic information, albeit small. But small goes a long way.
An increase of 0.1 volt change from 1.0 v is 1.1 v and is equivalent to a gain of 0.83 dB.
Now the idea of resonance is vibrating at a similar or like frequency.
When this happens there is an energy transfer or increase in beats ala a tuning fork when in resonance with a like frequency.
Like that, the harmonic resonates with a similar or like frequencies in the audio amplifier. There are many harmonics in the square wave form so they too, will resonate with whatever frequency(s) come into the amp.
What you here will be an increase in harmonic information as the signal passes through the amplifier to speaker.

"Generally, audio power supplies do not filter noise under 40 kHz, no?
You can put all the LRCs you want on a DC power supply and as many farads as you want. I will say that you will not find many supplies filtering under 20 Hz."

My goodness. Setting aside for a minute the absurd contention that injecting a low frequency AC harmonic that transmits through the supply is somehow helpful, from where comes the learning that a power supply cannot filter low frequencies? The first stage of the supply is a full wave rectifier - either a four diode bridge, or two diodes with a center-tapped transformer. The bridge does not care the frequency. When the voltage is positive relative to its bias, it conducts. When negative, it does not. It will rectify a 1 Hz sine wave just as happily as a 60 Hz sine wave. This is my last comment on this as the futility is obvious. P.T. Barnum was a smart man. If I were to spend money on Add-Powr, I would think it more beneficial to buy the company’s stock than its product.