More gains, better loading. But if you think a preamp is not your thing then a audio buffer also does the job with a little less gain. Some said using an audio buffer instead of a preamp actually sounds better. more transparent etc.
Why do preamps improve sound of CDP?
I have tried listening to my CDP through my preamp and bypassing my preamp going from CDP directly to headphone amp. If I go through the tape out of my preamp the sound is even nicer than direct from CDP to headphone amp. Why is this?