C'mon Maude.......... sigh.... . rejection........

Can someone tell me, or direct me somewhere that explains Common Mode Rejection in isolation transformers and how the dB ratings translate.
Also, is it better to bring in 220V to the IT then go to the subpanel at 120V? Is one IT at 5KVA better than two at 2.5KVA (or 3KVA)?
My system runs off a 30 amp, 220V dedicated line using a 3.0 KW ONEAC CB2338 isolation transformer/filter. If you can install one big transformer before the sub panel that would be better. There's plenty of info in the archives.

Noise reduction specifications should be given at different frequencies. Usually the specs are better as frequency goes up. I use a quad isolation transformer/filter array (Clear Image T4) for my line level components. The T4 uses toroidal transformers, which are better at reducing noise in the audio band. I also use an Audio Power parallel filter with the T4 to deal with transverse mode noise. It makes a very noticeable improvement. You can have this done w/ the Auricaps VenHaus Audio sells.