An iPod's cable uses a proprietary connector at the iPod end, so you can't use a standard USB cable. A standard cable may work between a computer and an iPod docking cradle, but I haven't used one to be certain of that.

Oh, and just to be sure we're all on the same page, you can't connect an iPod to the 990's USB input. You can connect an ipod with an analog cable. I've connected the headphone output of my iPod to the 990's tape input, although I'm told you can get better sound quality by bypassing the iPod's headphone amp (which requires a cradle to get direct access to the analog signal produced by the iPod's DAC).