741 Op Amp Audio Amplifier with Noise
You don't specify the length of cable with which you performed your tests so far...

But in any case, if you want to carry an audio signal with reasonable signal integrity over such distances, you will probably want to use balanced audio lines so that your common mode noise gets rejected, thanks to the differential property of this transmission scheme.

If you want to look into balanced audio you should start with wikipedia

https://en.wikipedia.org/wiki/Balanced_audio

But the German version "ist viel besser" (it has more pictures that are worth checking, even if you don't speak German).

https://de.wikipedia.org/wiki/Symmetrische_Signal%C3%BCbertragung

Also there has already been a post related to unbalanced (eq. electret input) to balanced conversion, using opamps. I think you should be able to implement such a system with 741 with minimal adaptations.

Unbalanced to balanced audio signal conversion