Here are some tweaks to further improve the EXP2581's audio performance:
Above: Carefully disassemble the unit.
Above: Replace output capacitors C502 and C602 with those of higher quality. I used Panasonic "FM" series here. Two images below illustrate how one can use the helping hands device to hold the board in position while one is manipulating (e.g. (de)soldering) components.
Above: A possible clue as to why this portable CD player has
decent audio quality: discrete audio output transistors. Most other portable
CD players I've seen use op-amps.
Above: Another view of discrete audio output section (middle right).
Above: Damp the printed circuit board and non-moving mechanical components
with tacky adhesive or rope caulk.
Above: The transport: a sub-system where mechanical damping is
important. This image greatly exaggerates the size of components. Use metal
picks and "surgical" tools to insert and sculpt damping compound.
For more information and price about some of the items above, click the link or image below...
Philips
EXP2581 Portable
CD Player with MP3 player
We use
Shure
E500PTH Sound Isolation Headphones for all portable audio tests
Philips 8.5" 16:9 Widescreen LCD Portable DVD Player with Apple iPod Dock
Philips 7" 16:9 Widescreen TFT-LCD Portable DVD Player