Sony will expand its Network Walkman line of digital music players later this month with the introduction of three new players based on flash memory chips.

The Sony players start at $90 for 256 megabytes of memory. Apple's iPod shuffle costs $99 for 512 megabytes.

All Sony's previous Network Walkman players have used hard-disk drives to store music files. The new players are set to debut at lower prices too.

Weighing in at 37 grams, the new Network Walkman players are circular in shape and measure just under 6cms in diameter and are 2cms thick. All three include an LCD (liquid crystal display).

Sony masses for March attack

The 256MB NW-E103, the 512MB NW-E105 and the 1GB NW-E107 - will be available in Japan from March 21 and should be available worldwide by the end of March, Sony said.

The introduction of these three players marks the start of Sony's expansion plans for the Network Walkman line. On April 21, Sony will launch an additional four players in Japan and these players will be available in the rest of the world by the end of that month.

These four players are all based on a stick-type form factor. They will be available with either 512MB or 1GB of memory and offer the option of a built-in FM radio. These players use a three-line OLED (organic light emitting diode) instead of an LCD as the main display.

MP3 support out-of-the-box

All seven of these upcoming players support MP3 music files as well as Sony's ATRAC3 and ATRAC3plus file compression format, which is used in the Sony's MiniDisc players and its online music store. MP3 support was missing from the company's first Network Walkman when it was launched in mid-2004. However, Sony began offering a Network Walkman player that supports MP3 late last year and has offered to upgrade earlier players to include the function.

Both battery life and number of songs that can be stored varies depending on the file compression format that users choose, according to Sony, which said the Network Walkman players offers the longest battery life when used with ATRAC3plus.

An ATRAC3plus file encoded at 48K bps (bits per second) offers audio quality that is equivalent to an MP3 file encoded at 128K bps, Sony said. However, ATRAC3plus files take up less memory which means users can store more songs in a player. This difference can be significant. A player with 1G byte of memory can hold 47 hours of music encoded in ATRAC3plus format but only 17 hours and 40 minutes of music encoded using the MP3 format, Sony said.

Long battery life

All seven flash-based Network Walkman players use AAA-type batteries. In power-save mode, battery life can be as long as 50 hours for the stick-type models during playback of music encoded at 105K bps in ATRAC3 file, Sony said. Under similar conditions, the circular-shaped models offer battery life up to 70 hours, it said.