The following project is a 2*50Wrms audio amplifier (2*120W peak). the design is fully digital, so power dissipation is very low, thus requiring only a very small heatsink.
in short the digital input signal is converted into a 350kHz PWM signal which is further amplified by a pair of MOSFET drivers. High efficiency, very loud and very small audio amplifier.

a prototype with SPDIF receiver, PWM driver and output drivers (from right to left) and a DSP with interface to a PC on top of the picture. since this is a prototype the circuit looks very messy and large.

The printed circuit board, soldered with components, and another empty one.

The whole design assembled and ready for building into a housing

The amplifier assembled in a housing made of a PVC tube and acrylic glass

The closed housing, still has to be painted black. size is 18 cm * 7 cm

Later on a small DSP for filtering and other tasks will be incorporated.
Maybe a computer controlled system, with display is used.

The whole amplifier can be powered by a 12 to 26V (laptop) power supply, the higher the voltage the more power is deliverable of course.

Remarks: some small adjustmenst still have to be made to make the design more efficient like adding some more low-esr capacitors in the power supply and so on. However the system is fully operational. as can be seen in the "open view" there is a small fan for cooling. this fan runs at a low speed and is necessary because of the closed housing. If the housing was left open this fan would not really be necessary.

UPDATE (feb 10 2009), the amplifier is in use and has a volume, treble and bass knob. A LED bar indicates volume level and bass/ttreble settings