Go to Applications → Utilities → Audio MIDI Setup . Set your USB device as the system output at 44.1kHz (not 48kHz). Serato works better at 44.1kHz on Snow Leopard.
If you are using an older machine and cannot upgrade the OS, these versions are your best options:
To make the software run "better" on an older machine like one running 10.6.8, follow these optimization steps Turn Off Sleep Settings System Preferences > Energy Saver
: If you are using Rane hardware (like an SL2 box), Scratch Live 2.5 is the legendary standard for Snow Leopard users, known for its extreme stability on older Macs. Community Perspectives
