As long as you only had one on at a time, probably wouldn't hurt anything. Keep in mind though, that of all the sources you input to the receiver, the phono input is probably the smallest. (lowest signal strength) Using extra cables, adapters, or switch boxes, might noticeably affect the sound quality, and/or volume of the signal. I'm not big believer of interconnects making a large difference in sound, but IMHO, the TT IC's is another matter, because it's such a small signal to start with.