Audio Static and DIstortion on MacBook Pro

I'm running 10.6.8 on my MacBook pro. I use it heavily for music, music editing, dance practice and dance class teaching. In the past week the audio coming from the audio jack has gone awry: hissing, static, popping, distortion. The built-in speakers work perfectly. Numerous cables, headphones and PA systems have been tried, so I know it is the audio jack and the computer at fault. Have tried gingerly blowing w/compressed air, no effect.

Is this a logic board problem and what's the next step?