Most high quality preamps do not have an internal DAC. I Don't recommend them, even if there is a slot. In general, you will get better sound by isolating functions. So, a preamp only being a preamp. Depending on your budget I'd looks a used Conrad Johnson, Audio Research or VAC preamps. These and other high end companies may outstanding preamps that will last for decades.
Using external DAC with preamp with built-in DAC
I need a new preamp. Most of the new preamps I've looked at do far have built-in DACs. My old one did not and I ran the digital outputs from my CD player into my DAC, then ran the outputs from my DAC into my preamp's CD input and it worked well. It seems like I should be able to do that with newer preamps with built-in DACs too. Will this still work? I like the sound of the DAC I'm using now.