Most often labeled AUX, AUX1, AUX2, etc. If the unit has an input labeled PHONO it likely has incorporated a phono stage and a phono preamp would not be necessary.

I think most RCA inputs other than phono, on common  amps and receivers, are designed to accept a 1-2V signal. Most CD players, tape decks, tuners, DACs, and phono preamps provide an output in this range. I have used CD, tape, and aux inputs interchangeably in the past. Do not connect any of these line level devices into a phono input.

Phono input is generally only for low level signal like a turntable. I recently blew the phono inputs in an older receiver by plugging a CD player into them. While it was playing. Couple of problems there. haha