[Updated] Is sound OK for you here?

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13" MBP Early 2011, 10.9.5

Crappy sounds occurs in both Firefox and Safari.

iTunes sounds is fine, after I play this video, sounds is bad in iTunes for a while but it seems to recover.

This happens both in speakers and headphones.

Sound is fine on iPhone SE. Sound is also fine on 15" MBP (same software as 13").

I will try to find other amazon videos.....