0.8% to 1.0% at rated power (20Hz to 20kHz).
Typically 100W to 120W per channel (depending on the specific circuit implementation and load). stk412530 datasheet
If you are troubleshooting a unit containing an STK412-530, keep the following in mind: stk412530 datasheet
Requires a dual-rail power supply (Vcc+ and Vcc-). It operates with a "high" and "low" voltage rail system characteristic of Class H designs to improve thermal efficiency. Load Impedance: Optimized for 6Ω to 8Ω speakers. stk412530 datasheet