I'm working on a digitally controlled preamplifier for quite a while now. The main features are:

• control by a 80C552-microcontroler
• 8 analog inputs, which can be independantly selected as line out and tape out.
• control amplifier with fader and 5-band-equalizer
• User interface by buttons, rotary encoder and graphical LC-display
• DSF-input for clock functions
• RC5-input for remote control
• Switched power output for power amplifier and other devices
• RS232-interface for control by PC

User interface of the preamplifier

The control of the preamplifier should be easy and intuitive. For this reason all funcions of the amplifier are controled by two pushbuttons and a rotary encoder, which has an extra build-in pushbutton. The basic funcion of the amplifier, the volume control, is set by the large turning knob. When it is pressed once, one of the eight inputs can be chenges for the line out. When pressed again, the same can be done for the tape out. All other functions (equalizer, alarm clock, etc.) are controlled by menues on the graphical display.

And it works :-) (01.03.2004)

The following pictures show the (partly) working preamp. Keyboard, display and I2C-bus allready work. Now I can change the volume with the rotary switch :-)