Does an isolation transformer improve a power cable?

Jafremman,

Richard Gray Power Company makes the "Sub station" isolation transformer in both 102/240V options. It has been in production for more than 10 years. Yes, these devices serve as a resivor for clean power reserve. Additionally, these devices clean your power coming into your dwelling from your power company's line-transformer. Very cool stuff indeed. Lastly, consider a dedicated line for your gear if you live on the "grid". Keep me posted & happy listening! JA

I am getting at is that, if this is a truly isolating transformer, then there is nothing upstream of it--forget about the house and all the big appliances.

No.... If you have a drag on your power system, like a big appliance you will have the same drag on the other side of the transformer. The electricity is not made at the transformer it just isolates it from the other side.
If you want to eliminate the reactive noise coming back up the ground you can lift the ground. I don't recommend doing it long though.

As stated above by another poster, these sorts of things are really used in hospitals, industrial use and labs that need to protect incredibly sensitive electronics.
Remember, in your amp there is already a transformer so theoretically your rails are already separated from the electrical mains. And those transformers are typically balanced out so you are getting those same effects of cancellation already.

Jafant, yes, I have had the 240V/120V Substation and the upgraded to the RM Pro for even more power and outlets. Yes, I have a dedicated 240 volt line, made from 10 AWG Romex and a 30 amp breaker.
Svan, even though power is not made at the transformer, it makes a lot of power available. Mine receives 240V via 30 amp service = 7200 watts. It steps the voltage down to 120V and preserves 4000 watts available for devices, and, as claimed by the manufacturer, it is all isolated from the house. My amps tell me this--they read at 121 volts constant. The Substation before it that outputted 2400 watts gave them 118 volts constant. No need to lift the ground--the house ground is not involved, again, as claimed--no ground loop issues at all. And this is what I am experiencing during listening. The amps are perfectly quiet and there is no effect on the sound from my house, including an electric range, the furnace, AC, 1/2 horse garage door opener, etc. If you read the claims made by the makers of these transformers, and if you believe them, then all that is left is to try them. I have them, and they have given me stellar results, and I live in a first-ring suburb with above-ground wires on poles that are > 40 years old. The neighbors' appliances don't bother me, either. But what I originally posted was a question about my new AC power cables, and I am answering yes to my own question, and I stand by this.

Yes, I have a dedicated 240 volt line, made from 10 AWG Romex and a 30 amp breaker.
01-01-15: Jafreeman

The 30 amp breaker does nothing more for the available power the ISO xfmr can draw from the main electrical panel than the correct size 20 amp breaker would. The total power that the ISO xfmr can deliver to the connected load is limited by the circuit breaker mounted in the front of the ISO xfmr unit. That breaker is there to protect the unit from a continuous overload or short circuit.
The current carrying contacts inside a 30 amp breaker are exactly the same size as a 20 amp breaker. The only difference is the thermal and magnetic trip unit settings.
The #10 wire was a good idea but it should be connected to a 2 pole 20 amp breaker.

There is a reason why the manufacture of the ISO xfmr specs a 20 amp circuit, there in a 20 amp breaker. He is following NEC Code which says a 20 amp rated receptacle can only be connected to a 20 amp breaker.

No need to lift the ground--the house ground is not involved,

I hope that does not mean a separate earth ground, ground rod, that is not connected to the main grounding system of the electrical service of your home.

There is a reason why NEC Code requires the neutral conductor of a separately derived power system, (there in the neutral conductor of the secondary winding of an ISO xfmr), to be connected to the main grounding electrode system of the main electrical service. It can be connected to it at any point. (Technically a safety equipment grounding conductor is not part of the grounding electrode system, though it connects to it.)

If you do have a dedicated earth ground that is totally separate from the main grounding system of your home I hope you did not break the equipment grounding conductor/connection that connects to the ISO xfmr unit from the 240V branch circuit that feeds the unit. That could be dangerous.

The Earth does not possess some magical mystical power that sucks nasties from an audio system.
.