Hidden Stereo Input Switcher

Brian from NZ

Issue 1, July 2017

A lot of older, classic cars don’t have stereos as a standard feature, and adding a modern one looks out of place (and is a lot of work!), so Brian came up with the idea of a simple input switcher for his 1963 Mk.1 Mini. The switcher has three inputs, an input switch to change them, and a volume control. The audio is controlled by a TDA7313 ST chip, with input and control run by an ATtiny44 programmed using the Arduino environment. A custom two layer board was made in Eagle, to suit the design. Adding to this, the microcontroller monitors one of the inputs (from a Bluetooth widget), and tone/balance/fader adjustments are made with a small add-on board that can be removed once the settings have been chosen. When combined with a standard amp, a Bluetooth widget, and an MP3 player you get a minimally intrusive, modern stereo! You can also see Brian’s Voltage Booster feature elsewhere in this issue!