It appears that the cable you have spliced into led to a phono preamp. It would seem that you need to find another avenue (line level) into the amp in order to get proper volume .
Thanks for the help. Looks like I got lucky here. When I got the unit, someone had already tried to splice something into the preamp. My theory is that they did so at line voltage and blue out the existing pre amp. When I tried to hook my record player direct, I got very little sound. When I tried to do it through my own pre amp, I got sound. From their, I was able to use an input selector and now I have four inputs going to the original phono input.
As a quick aside, I found this website really helpful (although admittedly a little out of my depth) on solving the whole stereo out to mono in problem. http://rane.com/note109.html
Thanks again for the help all.