SONY CDP-337ESD (released in 1987)This CD player was developed based on the design philosophy of the reference CDP 557 esd.The digital filter uses a newly developed IC (CXD1144) with an 8 x oversampling 18-bit digital filter.This newly developed digital filter has an extremely high-order 293 order preserving in salt capability, and achieves an in-band ripple characteristic of ± 0.00001 dB and an attenuation of 120 dB or more in the stopband. As a result, the generation of echo components caused by ripple can be suppressed to a negligible level. In particular, the reproducibility of the rising of a single sound of piano is improved.In addition, by increasing the sampling frequency from 44.1 kHz to 352.8 kHz by 8 times over sampling, the quantization noise in the audio band can be greatly reduced. At the same time, the distance between the music signal component and the unnecessary high-frequency component has been expanded to 332.8 kHz. Thus, the cutoff characteristics of the low-pass filter after D/A conversion can be relaxed, further improving the group delay characteristics.The D/A converter is equipped with a Staggered 4D/A converter system to improve the resolution of the 16-bit D/A converter.This method uses four D/A converters, two for each L/R channel, for staggered operation. These converters support sampling frequencies up to 352.8 kHz and enable high-speed, high-precision 8 x D/A conversion.