Nippon Precision Circuits, Inc. (NPC)^* has developed an LSI for editing 8-channel DSD^*1 (Direct Stream Digital) signals, the "SM5951AF", as part of its lineup of its LSIs related to high-sound quality CDs and Super Audio CDs (SA-CDs)^*2, with the support from Sony Corporation.

The SM5951AF inputs and mixes DSD signals (1-bit signal of high sampling frequency) of 8 channels by 4 systems, and converts them into DSD signals of 8 channels by 1 system for output. The sampling frequencies supported for the DSD signal are 64fs (2.8224MHz) for SA-CDs and a frequency two times higher than that, 128fs (5.6448MHz). Mixing at 128fs, which is two times higher than the frequency at which the existing products operate, is supported, which allows the LSI to be used for the future development of SA-CD software with the higher sound quality. This LSI is operated by two supply voltages, 3.3V and 2.5V, and is housed in 160-pin QFP.

The mixing coefficient of 8 channels by 4 systems of this LSI can be set from an external source as an arbitrary 24-bit coefficient. If mixing operation is unnecessary, an auto bypass operation to bypass the mixing processing unit without allowing noise to be superimposed on the original signal can be performed so that the output signal is virtually free from degradation.

In addition, the new LSI has many other functions, such as a function to output 64fs DSD signals for monitoring even during 128fs mixing. The LSI also has a function that can fine-tune the input/output delay time as well as a function to select externally input or internally generated mute patterns. These functions allow the SM5951AF to edit DSD signals with an exceptionally high sound quality.

The input/output format supports not only the straight DSD but also Manchester type coding DSD. It also has considerations for a high-quality DSD signal editing system such as selection of the width of the bus for bidirectional connection with a microcontroller using 8, 16, or 32 bits.

SD-CDs have increasingly made its way to general consumers as well as enthusiasts as players and mini-system component priced less than 100,000 yen that can play back an SA-CD. SA-CD software exceeded 1,000 titles at the end of last year and the price of hybrid SA-CDs with a CD layer that can be played back has dropped. Consequently, the growth of SA-CDs has increasing expectations in Japan's market. NPC plans to develop more LSIs that can process 1-bit signals for SA-CDs with a high sound quality.

^*: Main Office: 4-3, Fukuzumi 2-chome, Koto-ku, Tokyo; President: Yoshifumi Gomi

^*1: DSD (Direct Stream Digital) is the recording signal format of an SA-CD. Unlike PCM (Pulse Code Modulation) recording of a CD or DVD audio system, the SA-CD records 1 bit of signal at a sampling frequency of as high as 64fs or 64 times higher than that of the CD.

^*2: The SA-CD audio software is of the next generation like DVD audio software. While a CD discards sounds of audible frequency (20kHz) or higher when it records sounds at a sampling frequency (fs) of 44.1kHz, an SA-CD records sound waveforms at a sampling frequency 64 times higher (64fs) than the CD. As a result, an SA-CD can record sounds of frequency as high as 100kHz or higher. It can play back sounds as natural as you hear when listening to an analog record. In addition, unlike a CD, an SA-CD can also support multiple channels.

Product Name	Shipping of Sample	Sample Price	Mass Production
SM5951AF	March 2004	¥20,000 per unit	June 2004