uneven recording volumes

Hi all! I’m completely new to Audacity (version 2.0.6). I’m running Windows 7 x64 (Ultimate) and my system is a Gigabyte mobo, with an intel Core-i3 processor with 8gb ram. Recording from a JVC-Ql-A7 turntable (with a known good Stanton 681EEE cartridge and new stylus), through an old Sansui AU-317 amp (which has an excellent pre-amp section)I’m using the normal turntable input connections and the tape out connections to an M-audio Audiophile 2496 sound card. Recording level monitors show a slightly weaker left channel (showing -12db, while the right channel is -6db or so) and I am getting proper volume and sound through my speakers, both channels. However, in Audacity, I am showing a normal right channel signal, while the left channel is showing almost nothing for the waveform. Just slightly more than a flat line! Any ideas of why this might be happening? What should I look at?
I’ve recently upgraded to an entirely new system for transferring my vinyl. I have done several hundred transfers using my older XP computer with Cool Edit Pro (which won’t work at all on my 64-bit system). I have a couple of thousand LP’s left to do, and would like to get these “bugs” straightened out soonest. Thanks, in advance for your suggestions!

Have I got this right regarding the connections:

JVC-Ql-A7 turntable → Sansui AU-317 amp
Sansui AU-317 amp → speakers (sound is good)
Sansui AU-317 amp → Audiophile 2496 sound card (signal in computer is missing in left channel).

If that’s correct, then check the leads and connections between the amp and the sound card.

  1. close visual inspection of the leads and connectors, (dirt or corrosion can cause serious loss of signal)
  2. check they are plugged in securely.
  3. Retest.
    If the problem is still there:
  4. Swap over the left and right at the amp, and re-test. Note exactly what happens - is the signal still missing from the same channel?
  5. Swap over the left and right at the sound card and retest. Note exactly what happens - is the signal still missing from the same channel?