Monster Cable (and others I'm sure) makes two-input RCA adapters that can allow two of your sources to feed one input. I had this problem at one point and didn't go with this solution (got a preamp with plenty of inputs) because I was concerned I might have the two sources on at the same time (particularly if it was the tuner), and I wasn't sure how the preamp would deal with that much of a signal coming in to one of its inputs. Also, I was concerned about the sonic degradation which theoretically might come with the extra connection, but I'm probably too neurotic there...
One possible solution, of course, if you don't listen to the tape deck that much (or one of the other sources) is to merely disconnect that source except when you want to use it. A pain but if you really like the preamp it might be worth the bother.
One possible solution, of course, if you don't listen to the tape deck that much (or one of the other sources) is to merely disconnect that source except when you want to use it. A pain but if you really like the preamp it might be worth the bother.