Get a simple two-RCA to a single 1/8th inch stereo cable. Connect it from the
"tape out" on your receiver to the "line in" on your audio card.

Take some time to optimize the bit rate of the capture. If you try for a really
high bit rate and your PC won't handle it the sounds gonna be crappy. Picking a
bit rate that's too law will also be suboptimal.

Also, note that ripping from LPs will have to be in real time.

i am in the middle of recording a bunch of lp's at the moment. i
have a turntable that has stereo rca (phono) plugs connected via a
back-to-back rca socket adapter to a lead that has stereo plugs 1 end
and a 2.5 stereo jack plug the other which goes into my sound card mic
input. I use Audacity which is a full featured application that is in
the repository to record the LP's

I use audacity on occaison but never before for LP's.
Does audacity have an equalize feature to accomodate
the RIAA preemphasis that LP's have?

However, if you take the audio from your receiver rather than
directly from the turntable, that issue is circumvented.

I am no expert on this, just needed to copy some old records
however there is lots of add-ons and filters. I use the normalize
function then the amplify function and then export as mp3 tracks. I
record the whole LP (both sides) in one go then use the label option to
name the start of each track then export multi which then exports to mp3
and numbers the tracks. There is a good tutorial on the audacity website
about digitizing LP's.

I tried that, but I didn't get very satisfactory
results. I was going to try feeding the turntable output through a pre-amp, but
was concerned that there would be too much of an impedance mismatch between the
pre-amp output and the microphone input.

If you're coming out of a pre-amp or receiver, you'll need to connect to "Line
in" on your sound card. Also, chances are good that the direct output of the
turntable wouldn't match up with the microphone input.

yes i forgot to say that i did include a small cheap mic mixer
between the two which may have a preamp in. I did it so that it was
easier to control the levels, and it was lying around from my sons
disco days.

The catch is that vinyl records were recorded with "record
equalization": bass attenuated and treble boosted.This saved on the
track width necessary to record the bass frequencies and allowed the
inevitable treble "hiss" to be reduced on playback. When the levels
were reversed on playback it would sound right. Only pre-amps designed
for records have this equalization and your mike pre-amp will never
sound right.

According to this post:
Re: Hauppauge HVR-1500 HD TV card
Got it to work, ATSC only, no analog. Use Ubuntu 8.04, and install the latest
drivers from LinuxTV.org. Use very latest Me-TV to autoscan and watch.

You are out of luck with the approach you want to try.

I have my stereo connected to my sound card in both directions. I've recorded
from vinyl using Audacity. Mind you, it takes longer than just downloading an
MP3 using bit torrent...

How about a Stereo MiniPlug to Left and Right RCA adapter like this:

www.amazon.com/.../B00004Z5CP

And feed it through the on-board line in to the computer?

I have a mono miniplug version, which works fine for 78's - but never got around
to doing my vinyl. I avoided the USB player route, as the decks are pretty
basic - but I guess if you are converting to CD that isn't a problem? I'm
assuming the standard line-in is stereo, of course (I may be mistaken).