I couldn't find the specifications on the M-8, but if it's a stereo output mixer, a single coax cable will not work. Most mixers have stereo outputs and most sound cards have stereo inputs, therefore they require a cable that has a 3.5 mm (1/8-inch) stereo male connector/cable to the sound card that splits into two 14-inch or RCA mono male plugs at the other end in order to record in stereo.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)