Recording to test right and left channels...

The first Stereophile test disk has left/right tracks, in-phase and out-of-phase tracks, and test tones descending into the deep bass.

Vinyl test record or stereophile test cds or many other audio grade test discs and records too many to list.

I think you want   
IIsoTek   
The Ultimate Setup Disc

what are you unsure of?
Is this cartridge pin wire uncertainty?
Interconnects between turntable and preamp?
CD and preamp?
what?
If its beyond the cartridge just pull one RCA and see what sound remains (with the speaker disconnected and/or amp off of course)
Cartridge pins are a bit more complicated to diagnose.  Just make sure you follow either the color codes or the labels.  Standards can be found on the web with some simple searches.
G

I always use Take Five by Dave Brubeck you should hear the opening bit with cymbals coming out of the left channel.

Always easy to identify.