Can I use one turntable and one CD player?

Yes you can!

If you are using the SL 3, SL 4, TTM 57SL, Sixty-One, Sixty Two, SIxty-Four or Sixty-Eight set the dipswitch to line for the input you have your CD player connected to and set the dipswitch to phono for the input you have your turntable connected to.

If you are using the SL 1 you will need a phono preamp to boost the signal from the turntable to line level. In Scratch Live go to the Hardware tab on the Setup screen and set the Audio Input Level to line.