First, we need to assure everyone that no snakes were hurt in the making of the iPurifier AC and no snake oil is contained in the product, the only oil in the production chain is crude oil that provides the basics for the plastics used.
Is there a scientific basis for the function of the device? Certainly and we can measure significant attenuation of noise on our 2.5GHz RF spectrum analyser between the AC iPurifier inserted and removed.
Indeed using additional plug in capacitors to filter HF noise is not exactly new and tends to be fairly effective at higher radio frequencies. However both practicality and safety agency requirements mean the values of these capacitors have to be fairly low and their effect is thus limited to higher frequencies, often > 1MHz.
In modern EMC (electro-magnetic compatibility) testing, typically frequencies below 150kHz are not included and frequencies below 500kHz allow relaxed levels of noise emission.
So many power supplies (even linear ones) release fairly large levels of noise in these frequency bands while passing all EMC standards. And it is often these lower RF noise components that cause trouble in audio systems and that are not easily filtered inside of audio gear either (no matter how diligent the designer is).
Going active allows us to address especially this < 500kHz noise rather effectively. This way the AC iPurifier achieves very wide bandwidth compared to simple passive capacitor based plug in devices.
Our ANC uses a simple analogue forward circuit, which is very fast and is backed by and hands over to capacitor based passive filtering for high frequencies. So there is no "noise echo" or any such problem.
Where the active circuit is fast enough to provide the opposing noise it kills noise, where it becomes too slow passive filtering through capacitors takes over.
The use of active noise suppression in mains powered systems is not exactly new, it has been used in large scale industrial applications for a while. It's application in domestic power systems to reduce mains born noise at frequencies much lower than possible using passive means and specifically to improve audio systems.
A single AC iPurifier is fine to use and provides significant objective noise reduction. More than one unit in use increases the noise reduction in our measured tests more than the expected simple doubling/tripling etc. and provides wider bandwidth of noise suppression as well.
Further, as any noise has to "pass by" the AC iPurifier placing it between "noisy" devices and "noise sensitive" devices improves the situation more for noise sensitive devices than placing it at the beginning or end of a power extender strip.
A note on the surge suppressor. These devices are in parallel with the mains, they are not resettable circuit breakers - instead their function is to limit any voltage between live/neutral by drawing extra current.
This current drawn to limit the voltage to safe levels may very well trip conventional current based circuit breakers, but the MOV is NOT a circuit breaker in itself. It also needs no re-set, if the surge is over it simply stops drawing current to limit the voltage.