Yes it can be done. It's how I compare radios loudness and clarity. I plug in my iPods to two radios and let them battle it out. Waiting for my GF-767 and GF-777 to come home and battle them against my Conion C-100f to see who wins. I use the phono with the 1/8th plug on the other end. For the laptop the same. Neigbors love to hate me cause I'm continously doing it with the HK-9000 vs. Conion C-100f. I use the laptop with it's built in eq and my iPod on the HK. (for those wondering: Conion is louder, but HK is Bass happy after woofer swap).