Wiring up multiple components on a cambridge A5

I have a Pioneer CD player, a Kenwood CD Player and a new Sansui Streamer (WLD+ 201L) all connected to a cambridge A5 amplifier. The Kenwood is in the CD slot, the Pioneer is in the Tape 2 slot and the Sansui is in the Aux slot. Everything plays really well and sounds nice, except I can play the Pioneer by moving the slect button on to Tuner as well - why is that. That in itself is not a huge problem, but if I happen to be playing a CD on the Pioneer and change to the Kenwood, I can still faintly hear the Pioneer music coming through the speakers (very faint but I can be a bit of a perfectionist with my set up). Can someone give me some advice please. I've tried moving the wiring a bit but it's still the same.