Yes the RFI is on the line and yes it will sound better without, but its not like you think. It can be reduced with a transformer. The way a transformer works, the field in the primary induces a current in the secondary and because of the physics of the way this works only a certain frequency range makes it through. Which is fine because with AC its all 60 Hz. RFI is radio frequency, much higher, orders of magnitude higher, and so it doesn't make it through.
This however is only a small part of the story. Rather than focus on RFI or other noise on the line its much better to think only of things that improve sound quality. Forget why, focus on what. Because bottom line it really doesn't matter if its RFI or what it is, if it sounds worse it sound worse and if it sounds better it sounds better. So cut out the middleman and focus on the sound.
Then what you can do is actually listen, and learn. Listen to your system with the darn thing connected and on, and listen with it disconnected and off. If there's no difference either you're a lousy listener or it really makes no difference. Either way, if you can't hear a difference then who cares what anyone here says? Which also means if you can't hear a difference why spend money on some story about making a difference? That's how easy it is.
Then to find out what RFI really sounds like, for free, listen to your system some nice evening. Stop for a minute, flip off a bunch of circuit breakers, go back and listen again. That nice reduction in grain and glare you just heard? That is what less RFI sounds like.
Every wire everywhere is like an antenna. That's all an antenna is, is a wire. (A tuner tunes into one particular frequency out of this whole mess of frequencies. That's why we call it a, uh, tuner.) Radio waves everywhere induce tiny amounts of current in every wire. If you look inside your panel you will see they are all connected together. Flipping breakers breaks this connection. Each one disconnected is that much less RFI. You can even prove its RFI and not other noise by switching off circuits with things running and circuits things are not running on.
Okay so that's RFI. But you can also compare things like power cords and conditioners. Forget the stories, the marketing stories, they are just that, stories. Just try some and listen. What you want is that same sort of improvement you heard with the breaker test.
Or, if you heard no improvement, that's fine too. You get off easy. Long as you can live with the gnawing feeling there really was something there you should have heard. Because there was. And so now you know about RFI.
