line splitter (active/buffered) advice?

[newmz]

greetings. i've wondered for a long time now if it is (as i suspect) a bad idea to use those rca connector "Y" cables to split a line level from my pre-amp.

I'm in the process of adding a single subwoofer my pair of stereo speakers. So i need a single channel made of the summed stereo lines, in addition to the existing stereo line which goes to an active crossover.

What I really need is a reliable way to split the 2 stereo lines into 4 straight after the pre-amp, so that then I'll just use one pair to the existing power amps and one pair to be summed, etc.

All that I know about this really is that it's probably best done using opamps as buffers, etc.

Is it in fact a problem to use the 'Y" connectors to "passively" split the signal?

Can anyone recommend a website where I can get some schematics and info on the use of opamp buffers?