Signal Loss in Cable?

My friend uses a 3m signal cable (unshielded ordinary parallel wire) to carry the signal from his computer's Headphone out to the RCA inputs on his stereo amp.
My question:
1. What is the impact on the sound of such an abnormally long cable?
2. What capacitance / inductance will such a cord possess and which frequencies will suffer most?
3. What tangible gain will be obtained by switching to a shorter and better cable?

Anyone with experience or technical knowledge, do answer.
P.S. I find that dynamics and attack are limited, even though he uses huge flrs (12" + 3").