I have an Ion Profile Pro USB turntable. In addition to the USB connection, it has a set of RCA (red and white) output jacks. However, the instructions indicate that the output of the RCA jacks is line level, which is not strong enough to power speakers by itself. Most USB turntables that have aux outputs are like this, from the research I've done.
If your turntable has the RCA outputs, you'll need a small receiver or amp to power the speakers.