This part is a kind of semiconductor called AK4558.

Function of this product has 108dB 216kHz 32Bit CODEC.

Manufacturers : AKM

Image and pinout :

Some of the text within the PDF file :

[AK4558] AK4558 108dB 216kHz 32Bit  CODEC with PLL 1. General Description The AK4558 is a low voltage 32bit 216kHz CODEC for high performance battery powered digital audio subsystems. An internal circuit includes newly developed 32-bit Digital Filter achieving short group delay and high quality sound. In addition, “OSR-Doubler” technology is newly adopted, making the AK4558 capable of supporting wide range signals and achieving low out-of-band noise while realizing low power consumption. The AK4558 is ideal for a wide range of applications that demands high sound quality including Electronic musical instruments and Audio Interfaces. The analog inputs and outputs are single-ended to minimize pin count and external filtering requirements. The AK4558 is housed in a very small 28-p [ ... ]

AK4558 PDF Datasheet Download