The old purest will hook from a phono directly to a power amp with gain control, that's it...
That's actually the one source which absolutely requires a preamplifier (and its fixed EQ). Phono cartridges are akin to microphones or guitar pickups. They are transducers whose output is so low that there is far too little gain (as well as mismatched impedance) to feed a power amp. There is also a matter of applying the RIAA EQ curve. In order to get the most out of the medium, extreme EQ is applied to the master. That EQ is applied in reverse in the phono preamp. Phono inputs on a preamp are different than any of the other inputs. You should never plug a line level signal in to a phono input and never plug a turntable into any input *but* the dedicated phono stage.