Some Isolation Transformer Info:
The Isolation Transformer simply takes the whole electrical signal from the wall and stores it in a huge iron core on the input side. It then releases it to a smaller iron core on the output side that feeds your components. The key piece is when the electricity is released from the large input iron core to the small output iron core, it cleans the electrical signal according to the pF capacitance, in this case .001 pF is saying that the AC signal is cleaned (or background noise or soundstage) is reduced by 136 db. This is a drastic reduction. THE ONE THING that the Isolation Transformer DOES NOT DO is any kind of Surge Suppression.
The Power Conditioner only works on one leg of the electrical signal. Because it only cleans up one side (either the Hot or Nuetral side), it affects how the Power Conditioner makes the components hooked up to it sound. It's like using a stock power cord or a Dream State power cord or a Shunyata power cord, these affect the sound by the different materials they're made up of. The Power Conditioner USUALLY DOES PROVIDE Surge Suppression.
The bottom line is that the Isolation Transformer cleans the AC without adding any sound of it's own, and it reduces the soundstage noise a lot more than most of the Power Conditioners on the market.
I own an $1800 Transparent PowerIsolator power conditioner, and it doesn't even come close to what the Isolation Transformer did.
The bigger the Kva value, the better because of the AC storage on the input side, the bigger, the better the dynamics and bass power (headroom basically). 1.8 Kva is 1800 watts, 120 watts times 15 Amps. 2.5 Kva is 20 Amps, 3.0 Kva is 25 Amps. They say that the 5 Kva is the 'best' one to have for the headroom and ease, like a 500 horsepower engine will get you to 60 mph faster.
The lower the pF value the better: .005 pF = 126 db noise reduction, .001 pF = 136 db noise reduction and .0005 pF = 146 db noise reduction. Of course when you look at the website, the lower the pF, the more expensive. A 5 Kva with .0005 pF is $2,077.00 plus shipping. I paid $400 for the 2.5kva .001pF unit, though it was used.
1. Yes and no. Your components, like the XPA-1, also generate noise of their own that is sent back along the power lines. That noise infects other components in the chain. That's why many people say they cut the breakers on their refrigerator and microwaves when they are listening to music because it cuts out noise in power lines. By using an Isolation Transformer you are effectively isolating the components from everything else. They are not effected by other components that are plugged in, and they do no effecting themselves.
2. If you look on the surplus sales website, most of the Isolation transformers will tell you voltage in/voltage out. It usually will say 120/120, or 120/220 or 220/120... or any of the other ratings you may fine. Some go as high as 440 volts, others as low as 115. If you need it to work abroad, then look for ones rated 220/220. That means the voltage coming from the wall to the transformer is 220volts and the voltage leaving is 220volts. Often people will use a stepdown transformer from 220-110 to even greater benefit. This helps to prevent the transformer from becoming saturated and going into isolation.
It also means that a 2.4Kva transformer running at 220volts will output about 11amps rather than 20 as it does on a 120volt circuit.
3. Yes. I have used many power cables. I'll be honest, I was VERY skeptical myself at the effects of power cables on a system. But boy was I converted when I brought some home. I have used the upper echelons of Shunyata, Tara Labs, Lessloss, Virtual Dynamics, and a few others. Purist also makes good, but expensive, power cords.
They make the biggest different on CD players or transports. A large gauge power cord makes a good difference on power amps too -- the XPA-1s love a good power cord, the standard cords suck (for lack of a better term).
The basic reasoning is that the power from the wall is what the audio signal is created from. With a CD player, some of that current is used to create the laser that reads the CD, another bit of current is used to create the digital signal, and a third bit of current is used to convert that to an analog signal. If that power coming from the wall is noisy, then the signal you get from the CD player is noisy. This is why power supply design is so important, it helps to filter the noise coming from the wall (among many other things).
A good power cable should also help filter the power coming from the wall by use of capacitance and low resistance (among other things. If you want more info you'd have to call me because it's too much to type up). That being said, I've heard power cables in my system make as big a difference as a component change. They make a bigger difference than speaker cables and interconnects -- depending on the budget you're running anyways.
I am a believer in power conditioning. It makes a huge difference in my system. I'll probably buy another isolation transformer and sell my power conditioner though -- the isolation transformer is more neutral and actually does a better job at cleaning the power. My advice: buy power cables before a power conditioner. A power conditioner will help bring your power cables up another notch.