Some month ago I planned to build an amplifier. The amplifier should be built as small as possible. So I decided to use a 300W switched power supply to drive the amplifier. Because of the inrush current of the supply, a softstart unit was needed.

My research at the internet revealed, that there is no unit which would fulfill my needs.
So I decided to develop it by myself.
The concept of this unit is based on the ATTINY24 microcontroller which programmed statemachine will start first the main power supply and after that the amplifiers. This sequence is necessary, because the big capacitor of the amplifier (>50mF) will cause the supply in short circuit mode.

For a comfortable use, there is a remote control ability achieved by the µC. Via IR interface a servo motor of the volume pot could be controlled. Of course, I designed an automatically starting trigger of the amplifier, if there is any audio signal on the line inputs. Also an additional supply for the preamp is included on the PCB.

So thank you for reading this and be sure that constructive criticism is always welcome...