But if you use tone/balance controls then its not a pure signal anymore. This altered signal now has the distortions, harmonics are changed. You will be able to hear these subtle changes on a high end, resolving system with discerning ears. ...
In a high-end, well-treated room.
But Manoj, the point is that we are talking about
imperfection.
However good your system is, and however good your room is, if you have lived long enough to afford all that, you probably don't have perfect hearing. You probably have some high-frequency loss, your ears may not be equally sensitive. Tone and balance controls can help.
In fact, this is just not about the system: it is about the environment, and about us. Whether these things are useful or not does not really depend on the cost, or resolvingability, of the equipment. They are to correct things that cannot be corrected by simply increasing the budget.
And where do you draw the line? Where, exactly, does your
pure signal
cease to be pure? A certain amount of circuitry is ok, but beyond that is not?
Balance controls certainly change the sound. By definition, they change the sound. Is that sound now impure? You can say that it is no longer what the recording engineer intended it to be, but then, was it ok for you to buy equipment that is not simply 100% transparent? Which changes the sound from what it was intended to be? And ok for people to use cables as tone controls, but to shun tone controls and refuse to even talk about the box which is designed and engineered to finely customise the sound?
you is not
personal, of course. For all I know manoj.p might value transparency above all things, and have no need for these extra knobs. I'm talking about tendencies and ideas that we all have to some extent ...which is why I ended up with an amp without tone controls. But now I have ears that make a mockery of that.
It is the lucky and careful few that can talk perfection. Then there's the rest of us...