MPEG-Audio-Player

Home stereo CD/MP3-player

Since May 1998, this selfmade apparatus is part of my hifi set. It is a CD player with integrated MPEG audio decoder for playing compressed bitstreams from CD-ROM. The interior consists of standard PC components mainly. Not very exciting really, but practicable.

You can purchase a DIY-kit including a backlit LCD (2x16 characters), software and instructions. The price is 15 EUR including postage within Germany.

Here are some technical details:

Case: Metal chassis 43.5cm x 8.7cm x 27cm with transparent front plate.
Power supply: In the beginning, I used a conventional transformer with voltage regulators, but its efficiency was only about 50%. So I finally preferred a switching power supply (max. output 65 Watts) with standby feature and regulated fan (hardly noticable). The power consumption of the whole device now comes to moderate 17 Watts.
Mainboard: 486 Baby-AT-size, 256 KB Cache, PCI (unused). Note: The BIOS (here: AMI) must boot without graphics adapter and keyboard!
CPU: Cyrix 5x86-100, 3.3 Volt, running at 75 MHz without fan.
Memory: First 32 MB RAM, now 16 MB (even 8 MB would be enough). Used as a ram disk and for caching.
Harddisk: 2.5 inch, IDE, 40MB. The harddisk is mainly required to boot the system and is switched off after copying the software onto the ramdisk. However, MP3-songs can also be played from the harddisk.
CD-ROM-drive: IDE, Double speed (single speed would be sufficient).
Soundcard: Miro PCM 10. Not a highend product, but giving a very good impression in contrast to many cheap boards. Only it's a pity that the integrated wavetable ROM is now unused. There are grounded sheet metals to both sides of the sound board to reduce potential noise.
Display: A 2x16-character-LCD-module is connected to the parallel port of the mainboard (scheme). A simple Pascal program outputs text from a file or the command line.
Input: Each of the five status lines of the parallel port is connected to a pull-up resistor and can be grounded by pressing the corresponding switch on the keypad. The same logic is used by the digital-joystick interface presented on my Portfolio-page. A character device driver ("KEYPANEL.SYS") enables application software control via input redirection.
Operation system: MSDOS 5.00. The "Master Control Program" (Tron?) is a batch program which consists of different parts for handling normal audio CDs, MP3 files, browsing directories, doing file transfers etc.
MPEG-Decoder: MPXPLAY 1.46 (August 2002). MPXPLAY works very efficiently and decodes Layer II and III bitstreams. Since version 1.21, it cannot be controlled via input redirection anymore. Therefore a TSR program emulates keyboard input by polling the port status and manipulating the keyboard buffer.

DAMP

A few pictures:

	Front panel with the glass plate removed. Illumination is done by 12-Volt-bulbs. The current key assignment is displayed on the lower LCD line.
	Apart from the audio outlet, an AT-bus-slot for the "graphical diagnostics adapter" (VGA-board) and a serial port are located at the rear.
	View on the "high density" interior. The mainboard is located on the bottom, occupying most of the area to the right side of the power supply unit.
	In order to mount the sound board horizontally, a bus adapter (as found in some old slimline style desktop computer cases) is required.

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