Hi
Sooner or later an audiophile trying to extract the maximum from his/her system faces the issue of Power Quality. Most people in Information Technology have faced it one way or another and it is dealt with in this area.
It is not so much an issue of how stable your voltage is, although that is one parameter but how clean the power brought to you is. Your equipment suppose a sinusoid, it rarely gets that from the mains. It suppose a stable frequency, it does not. It also suppose the presence of just one frequency, it often gets the whole Electro Magnetic spectrum.
Trying not to repeat what I already wrote in this forum (I will search it). You get a line, several kilometers long from the generating station to your house. Along the path of this wire there is a lot of noise, most of these man-made: Radio and Television Towers and nowadays seemingly every other centimeter, a cell tower plus, the numerous wireless everything people use along the path of these lines… Meanwhile there are millions of electric motors, Digital things and other noise makers sending their noise back on that same line that ultimately will come to your house … To have a good idea, just get an oscilloscope and look at the waveform from your mains, any mains, anywhere in the world. You will likely to see a rather “dirty” signal and this gets into your gear. Some are less affected by it but it is my subjective experience that they are all affected one way or another. So it is essential in my opinion to get your gear the purest AC possible. I don’t know of any formal studies on the impact of Power Quality to sound Quality but Recording Studios are pragmatic about it and take all precaution to insure clean power to their system and for the most part they don’t rely on fancy power cords: They rely on addressing the fundamentals.
First find out the maximum draw of ALL your gears. Emphasis on maximum. Let’s take an example of a 100 watt/ch Class A SS amplifier. Its maximum draw when delivering 100 watts at 8 Ohms to both channel simultaneously is probably 800 watts total but if it doubles its output in 4 ohms it requires 1600 watts then … so if you have say a speakers that can dip into say 2 ohms you amps will want to draw 3200 Watts …total, by the way most normal 20 amps circuit breaker will trip by then but if you are one of those souls who have discovered the advantage of using 240 Volts rather than the usual 120 VAC (thinking in US terms here) you , yes it will want to draw that much from the mains … So yes think in term of maximum power drawn by your gears under the worst conditions .. Preamps won’t ever draw that much nor TT , Tape Decks, CD players and DACs and processor but you get my drift. What you get then is the rating of your system … I think isolation transformers can do a good job, being inductances, they will present a very high impedance to the nastiest that ride on the power lines and present the system with a cleaner AC. They must be properly sized though, else they will restrict current delivery to the amps, thus the often mentioned complaint of constricted dynamics, one hears with the use of power conditioners, especially those “audiophiles” which for the vast majority are not adequate to power any serious amp I know of only two purely audiophile solutions which correctly address the problem by re-generating the AC: The PS Audio and the Burmester Line Conditioner. Both are not powerful enough to power a medium power system or say a 200 Watts/ch class A amp.
I have often voiced my preference for Professional Double Conversion Telco or Data Center UPS types. My favorites are the ferroresonant models made by Lorrain now Marconi (there are others) in the absence of these unwieldy beast, they are truly big and noisy, Double conversion UPS made by APC are to me the better alternative. They seem to be shunned by us, audiophiles because, they lack the audiophile creds. Maybe if one well-regarded audiophile designer were to modify one of these with the addition of the (ineffective but expensive) cryogenically-treated outlets, fancy faceplate and capacitors, then sell it at several multiple of its original price .. we would accept these but …
Another very important aspect I have often forgotten to mention in my posts about quality is Grounding. Grounding is never a trivial undertaking and in itself a specialty. At the very least make sure you have a very clean ground system of the lowest resistance achievable, lower than the usual 25 Ohms recommended by the NEC. I would have liked much lower than 5 Ohms but this is not always easy. Depends on the terrain and the likes... but make sure it is less than 15 ohms. The ground is the reference and the sink. The lower the resistance to the sink, the easiest garbage flows down to it. The ground is where the system would like to dump all the garbage, if you don’t have a good ground then the system has difficulty getting rid of the garbage and frankly one can hear it.
The expensive approach of fancy power cords is not a solution, not even a band-aid, they don’t work for the most part except in our heads and take away financial and technical resources that could have been used in the general scheme of better power quality.
I sincerely would like to see more formal and objective studies on the importance of PQ in the context of an Audio System. I would like to see more awareness from the Audiophile community on the subject as well. It seems some people are realizing the benefits of such… it’s all good then …