This part is a kind of semiconductor called STK4161V.
Function of this product has AF Power Amplifier.
Manufacturers : Sanyo
Image and pinout :
Some of the text within the PDF file :
Ordering number: EN2135B Thick Film Hybrid IC STK4161V AF Power Amplifier (Split Power Supply) (35W + 35W min, THD = 0.08%) Features • Pin-compatible with the STK4102II series. The STK4101V series use the same package and are available for output 15W to 50W. • Built-in muting circuit to cut off various kinds of pop noise • Greatly reduced heat sink due to substrate temperature 125°C guaranteed • Distortion 0.08% due to current mirror circuit • Excellent cost performance Package Dimensions unit: mm 4040 [STK4161V] Specifications Maximum Ratings at Ta = 25°C Parameter Maximum supply voltage Thermal resistance Junction Temperature Operating substrate temperature Storage temperature Available time for load short-circuit Symbol VCC max θj-c Tj Tc Tstg ts *1 VCC = ±30.5V, RL [ ... ]