btw,i was thinking about that:
assuming the high input impedance of the opamp, can i figure myself the fact of zero input current, then this part is not really "loaded" and i can pass directly the same terminal to the output branch that is tied to the audio amp???
am i severely wrong about that??? (btw maybe i"ll verify it with crocodile clips and wire from the only jack i got available this very afternoon at my office if i have enough place ^^ )
The input current is not zero. It is however small enough that you wont care in this case. On the opamp datasheet, the input current will be listed as Ibias, Iinput bias or similar. For bipolar opamp input stages, this is on the order of 10s nA to uA's, for Jfet stages it can be 10s pA to 1nA and for CMOS, fA to pA (specs limited by manufacturer testing capability since it's so small)
In your application, you can tie this node to many places with little fear of loading it down. Be sure you do not exceed the input common mode voltage range and you should be ok.
BTW, for future projects, the 741 sucks --there much better *and even cheaper* devices available today if you get into more serious work. Good luck