convert phono leads to usb?

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You need a USB audio interface. The smallest I've seen (which I have) is an Edirol UA1X (Edirol make stuff for musicians and video editors and are well respected). I also have a Soundblaster MP3+ which is fairly small but discountinued. Creative do some other Soundblaster USB cards which are larger.

I've seen the M-audio Transit for under £50 (M-Audio also make well regarded musicians recording interfaces). This is also small.

Another small option are cards that plug into the PCMCIA slot. These are more expensive generally and Creative are the only manufactur of consumer interfaces (what we musicians call stuff not just designed for music recording) that I've seen with one.