This unit replaces the original microcontroller in the Cambridge Azur 340A amplifier.
Cambridge Azur 340A is a quite nice integrated amplifier from Cambridge Audio. However, it is missing a few components, that are only needed in case of an over-voltage on the inputs.
That situation occurs more often than one might think, especially when using an ungrounded PC as audio source, and particularly if hot-swapping the audio cable. A fact that a friend of mine became aware of the hard way. The first time, "only" the input selector IC was damaged. I helped him replace it, but a few weeks later, he did it again...
This time, replacing the input selector wasn't enough, also the microcontroller was fried. I had some contact with the Cambridge Audio spare part department, who were nice and helpful, but unfortunately the part was no longer available. My friend surrendered to Sony (let this be a lesson, Cambridge!), and the Azur was mine to keep.
Uncapable of throwing away an otherwise perfectly functional amplifier, I decided to write new controller firmware myself. The original microcontroller was a PIC16F72, but since I am not very fond of the PIC family, I decided to use an AVR instead. And since they are not pin-compatible, I had to make a custom PCB that acts as an adapter between the AVR and the original socket.
All of the original functions, plus an animation on the LEDs at startup :)
The system is built around an Atmel ATMEGA8 microcontroller. It continously monitors the inputs, and controls the input selector, LEDs and volume control.
The input selector is a general purpose analog function switch array from Toshiba, TC9163AF. This IC is serially controlled from the controller unit, which reads the buttons on front, and the input from an IR remote control receiver (RC-5 coding). The controller unit also controls the motor-driven volume control through a BA6218 reversible motor driver from Rohm.
As a final update, I added four zener-diodes to the aux-input. Hopefully they will prevent future accidents of this type.