Is the mixer analog or digital? If analog then the output jack is fine. The signal has to be converted to analog at some point and the built-in converters are probably high definition depending on your laptop model.. If the mixer is digital then you might want to keep the signal digital until it reaches the mixer's converters. If you were to get a usb external sound card, many of them can pass on the digital signal. Some of the laptops can too but it depends on the model.
Jim Coates -- 15 years on the Dell Laptop Audio boards -- since 2/6/04