Ptss,
"...if the ac is perfect no unit will make any difference".
I can certainly appreciate that there may be some conditioners around that aren't particularly effective at making a noticeable difference in sound quality, but, FWIW, I personally believe that a big part of the underlying truth of the topic generally has as much, or more, to do with "electrical noise" as it does with the usual things like inductance, resistance and wire length/geometry and so on, whether we're talking about balanced applications or no.
Most of us are at least passingly familiar with the importance of the idea of "digital self noise". But, maybe not many of us have looked beyond that long enough to see that actually All our components pollute the electrical system (both in connection with AC and DC). The digital stuff tends to be noticeably noisier, but we've learned that the principles that effectively deal with digital self noise can also be good for the analog components. But, it really goes much deeper than that. When we start looking at exactly what it is about the components that is causing this, we find in the end that it is nothing, or rather everything - every little cap, every resistor, transistor, diode, etc. each part contributes a small, but significant, amount of electrical noise. It's believed to be triggered by vibration. This is the vibration found in literally every electrical circuit on earth. When power is present there is vibration...like with that occasional street, pole transformer that you can easily hear humming from more than 50 yards away. But, if this is true then that means that this "self-noise" phenomenon is nothing particularly unique to our gear...that there are indeed caps and transistors and microprocessors in anything and everything that we plug into an outlet anywhere in our home. That all our cellphone chargers, computers, coffeemakers, appliances - everything from our HVAC's to a nightlight is also continually pumping out garbage into the electrical system of the home.
And, wouldn't you know it, as we learn as hobbyists in connection with our gear, the better the individual part, the lower the noise. Why use a cheap cap in your power supply when a more expensive one may well have better noise characteristics, yes? IOW, cheap parts will translate into worse noise. So now, just how much noise do we suppose is really being created by that walmart, programmable coffeemaker we bought on sale a while back?? Or that new, energy saving bulb?? And it all adds up. The more stuff plugged into your home, the more electrical noise there is to contend with. It's as simple as that. The idea that the real culprit is "dirty power" that comes from outside the home ends up being at least something of a myth (most often, anyway). But, all this is why I would say that, in my opinion at least, NO AC system should be considered perfect. I believe it to actually be an impossibility, in terms of audio sound quality (...or video quality, FTM). Even under ideal laboratory conditions and even with audio systems that operate entirely off the grid. From this perspective anyway, any electrical system can be expected to be an inherently noisy environment.
Regards, John
