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Reuse an Old Phone and Old Speakers As a STEREO

Turn a pair of old speakers and an old smartphone into a stereo installation with radio, mp3 playback podcasts and internet radio, using a few common components that cost less than 5 euros in total! So we have this collection of 5-10 year old smartphones that are partially functional but impractical: the memory is too small, the Android version is too old and typically the battery capacity is down to a tenth of its original. They are great for music playback though! Many have a built-in FM radio, a built-in mp3 player and if it connects to the home WiFi, it can also play internet radio, podcasts or Spotify. The built-in speaker is tiny, but it can be amplified. If you have a stereo with an input jack or that connects with bluetooth, plugging it in is all it takes. If not, read on!
So our stereo died. But I kept the speakers. I tried the tiny and cheap (<1EUR) amplifier module that are based on the PAM8403 chip. The sound quality is great, and there is more: the amplifier is so small that it doesnt need its own box: it easily fits on the back of one of the speakers!
The touchscreen interface of the phone is far superior to the lousy user interface that most stereos com with. And local radio doesnt match quality podcasts that are easily followed with the phone. However, there are a few pitfalls in the use of the PAM8403 module, so here I share my setup that worked well the first failed attempts.”

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