This part is a kind of semiconductor called STK4121V.

Function of this product has AF Power Amplifier.

Manufacturers : Sanyo

Image and pinout :

Some of the text within the PDF file :

Ordering number : EN4477A477 Thick Film Hybrid IC STK4121V AF Power Amplifier (Split Power Supply) (15 W + 15 W min, THD = 0.08 %) Features • Built-in muting circuit cuts off various kinds of pop noises. • Current mirror circuit provides low distortion (THD = 0.08%). • Pin compatible with the STK4102II series, forming a series of products with output powers from 15 W/ch to 120 W/ch. Specified Transformer Power Supply (RP-22 equivalent) Package Dimensions unit: mm 4040 [STK4121V] 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 max Tc Tstg ts VCC = ±21.5 V, RL = 8 Ω, f = 50 Hz, PO = 15 W Condition [ ... ]

STK4121V PDF Datasheet Download