Max number of USB turntables?

Don't know why I can't figure this out but does anyone know what the maximum number of USB turntables you could hook up to a mac is? While we are at it is there a multi-channel Firewire/USB hub or audio card you would need to do this and what would be the best software to use? i.e. Logic etc. Bottom line I want to know if I could simultaneously record like 12 turntables into Logic at once.

In theory, you can hook up to 127 (?) USB items into the USB bus. However, each item would require its own power source. So, if you have, say, 10 x USB turntables, each with its own power source, and hooked through a powered dock, USB2 hub or mixer, in theory you could blend sound from each of them simultaneously. How you would coordinate the sound from each - ?????

BTW - what type of USB turntables might be used?