Game Changing Tweak

One other thing ADD-Powr says in describing their technology:  
"

• They generate and propagate low frequency signal information to affect harmonic change to audio signals.  

• They super saturate the AC line voltage with harmonics to affect a 1 to 5% increase of the voltage peaks delivered to the power supplies of system components."

Why exactly would you want to increase voltage peaks?  Stable voltage is extremely desirable, peaky voltage not so.  The vast majority of PQ problems are voltage related, either a sag or a surge, and those can mess mightily with electronics.  Also, how does super saturation with harmonics increase voltage?  Harmonics are undesirable.  Now, if you are doing PF correction, that will slightly lower voltage by lowering current flow, but they also specifically say, "

     ADD-Powr products are

    Electronic harmonic resonators.

    They are not AC power line conditioners".

Honestly, the more I read this on this site the more it screams Snake Oil.

Geez, where were you guys on the thread about improvements from AC power cords?

Current harmonics occur on power lines due to non-linear loads, of which there are many.  Do they affect the sound coming out of your system?  I read through ADD-Powr's website. They claim,
"A complex wave "disturbance" rides  along the AC line. Since it is a low frequency signal, it is not filtered away by power supplies, such as a/v component power supplies.  Instead, it passes through the filter stages and becomes part of the DC reference supply voltage."

What low frequency signal are they talking about?  They don't say. This claim seems bogus to me, if for no other reason than they don't publish any actual data.  I couldn't find any product specs.  And, if it were a real thing, it would be easy to demonstrate.  Specifically:

1.  Show me a frequency graph of incoming A/C power (both the 60Hz  and whatever harmonics you want to include) and the corresponding frequency graph of amplifier output.  

2. Now introduce the "device" and show me the same graphs.  This kind of before and after will show both the frequency domain and the scale of the impact of the high pass filter.

Nada.  Nothing.  A picture says a thousand words, but only if there's something to show.

@bemused--  You wrote:
"From perusing the web site, ADD-Powr is appears to be about increasing "energy", or the voltage of the audio signal through the generation of harmonics on the reference supply that are too low in frequency to be filtered away by the component power supply. They more or less resonate with similar frequencies in the audio signal. If the fundamental signal is low enough, then its resonant affect will be evident throughout the audio band. The driving fundamental must be a complex function composed of sines and cosines in various phases - that is the Fourier series. Or...perhaps it can be simply be a square wave!

That explanation makes sense."

It does not make sense to me.  Can you explain it?  What frequency levels are we talking about, exactly?  Power comes in at 60Hz.  What low level AC frequency will resonate through a DC power supply?

@millercarbon--

Please refrain from obscene generalizations about people. When I say something seems like snake oil I am most certainly NOT saying that my mind is made up, that everyone else are suckers, and that I am not going to listen and learn.

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.  There are a thousand tweaks out there and my time is limited, especially I am going to spend it listening to things that have a reasonable chance of making a difference. Especially regarding improvements from AC side tweaks, which have nothing at all to do with the musical signal.   Unless your power quality is terrible, AC side stuff just isn't going to make a difference.  Running your system off a quality UPS will give you perfect sine wave power, stable voltage, and no harmonics.  Problem solved.

For goodness sake, would you not be skeptical of, say, an amplifier designer who says their amp sounds better because it's inhabited by quantum level musical pixies?

Hey, if someone else hears a difference, more power to them, though, with the ever present caveat of awareness of confirmation bias.  If you don't do double blind testing, how do you know you actually heard it?  By all means, go by what you hear - I certainly do - but don't you want to be certain that you really heard it?