This part is a kind of semiconductor called STK4050.

Function of this product has AF Power Amplifier (Split Power Supply) (200W min / THD = 0.4%).

Manufacturers : Sanyo

Image and pinout :

Some of the text within the PDF file :

Ordering number: EN 4807A Thick Film Hybrid IC STK4050II AF Power Amplifier (Split Power Supply) (200W min, THD = 0.4%) Features • Compact package for thin-type audio sets • Member of pin-compatible series with outputs of 20 to 200W • Easy heatsink design to disperse heat generated in thintype stereo sets • Constant-current circuit to reduce supply switch-on and switch-off shock noise • External supply switch-on and switch-off shock noise muting, load short-circuit protection, thermal shutdown and other circuits can be tailored-designed. Package Dimensions unit: mm 4051A [STK4050II] Specifications Maximum Ratings at Ta = 25°C Parameter Maximum supply voltage Thermal resistance Junction temperature Operating substrate temperature Storage temperature Symbol VCC max θj-c Tj [ ... ]

STK4050 PDF Datasheet Download