You have to consider the type of cartridge on your TT. If it is magnetic it will not produce enough signal for the standard computer sound card. I run a mag cart with small wires and very short leads into my preamp and then get a signal strong enough for the sound card. On 78 records I have a different setup. I can run a ceramic directly into the sound card.You can see:
http://dvautier.home.comcast.net/audio/audio.htm
and maybe:
http://dvautier.home.comcast.net/lp/lp.htm