Ah, turntable calibration, now you're in for trouble.
First, you're left channel problems could be a wiring issue. You should have four wires that connect to the back of the cartridge that are attached to the back of the cartridge's posts with tiny clips. Make sure all the clips are attached all the way and not loose. If you have any loose clips you need to carefully remove them with tiny needle nose pliers, stick a toothpick in where the post would go and tighten them with the pliers, then reattach (remember which color wires were attached to which posts). See if the tighter connection cleans up the left channel.
You must also align your cartridge so the needle tracks the record correctly in all dimensions and properly set anti-skate to insure good vinyl playback with proper stereo balance and minimizing surface distortions. You will need some tools to do this:
set up record (includes cartridge alignment protractor and instructions),
stylus force gauge, bubble level, small magnifying glass, small mirror, great lighting (light a bendy arm DJ lamp), small screw/hex drivers and pliers.
I highly recommend checking out
21st Century Vinyl DVD by Michael Fremer. He goes over the whole cartridge alignment process with the above tools and makes it easy to understand. I
reviewed the DVD too when it came out a few months back.
Another good set up guide with lots of Thorens info.