Instructables

RaspbAIRy - the RaspberryPi-based Airplay speaker

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Step 2: Electronics

  • Stereo to Mono
Following the great guide of Dennis Bohn "Why not Wye", I chose to integrate an easy summing circuit or actually two, one for each audio input.
 
  • Input Switch
A simple dip switch (ON-ON) for selecting the audio input for the amp. I added this to be able to connect other audio sources and to use the device as a 'normal' speaker, independent from the RasPi.
 
  • Mono Amp and speaker
The selected amplifier was wired according to the datasheet. Basically it accepts input voltages from 5 to 12V DC and a mono input signal through an optional potentiometer for volume control. I connected a 8Ω broadband speaker, which sounds surprisingly good for only 10€.
 
  • Power Supply
I chose to integrate two separate power units to be able to independently turn off the amp/speaker while keeping the RasPi running. This is mainly due to the boot time of Raspbian of about 30-40 seconds. Because I had them laying around I used two plug-in adapters, one providing 5V DC (max. 2500mA) for the RasPi and the other providing 12V DC (max. 1500mA) for the whole audio setup.

louieaw1 year ago
Quick question. Trying to do a similar project. Is it necessary to have the two inputs (The RPi and Aux) on separate grounds? Why not just connect the two and have one SPDT switch?
sisisisi251 year ago
I don't want to ruin your day but the power LED is shorted. You have to connect it to ground.
zwuckl (author)  sisisisi251 year ago
Oh my, you're absolutely right, thanks. I will have the diagram corrected by tomorrow. The actual LED is wired correctly ;)