Mini Boombox Media Player With LM386-Powered Speakers

I got this car radio replacement module mp3 media player but it did not come with a car. So, I used a pull box to provide housing for the mp3 player. The result is a Mini Boombox MP3 Player and FM Radio. The speakers are powered by a single mono LM386 IC 20x-gain amplifier minimal circuit.

My mini boombox mp3 media player.

My mini boombox mp3 media player.

Top-Firing Speakers

With speakers at the top, the sound easily fills the room. You can safely keep the boombox next to you but your face will not be buffeted by the sound.

With speakers at the top, the sound easily fills the room. You can safely keep the boombox next to you but your face will not be buffeted by the sound.

I have a modded phone charger with a 2.1mm DC plug but I also created a USB-to-DC cable to power the boombox from a PC USB port. The module is rated at 12 volts but it can boot up at 5v from a USB port.

An USB to DC cable.

An USB to DC cable.

I can also power the boombox with a 9v battery. For that, I have created a modded battery clip with a you-guessed-it 2.1mm DC plug.

A 9-volt battery can make the boombox truly portable.

A 9-volt battery can make the boombox truly portable.

The boombox can play MP3s from SD cards, pen drives or any storage device with a USB port. It also plays FM radio. (I fashioned an aerial out of the antenna of an old RC toy remote.) The mp3 module had a line input connector and I added a 3.5 mm stereo plug for plugging in an external audio source such as a phone or a tablet.

Verdict
The speaker parts that I had used are not the best or the loudest that I have. I had to settle for smaller ones that would fit inside the pull box. Still, they are quite loud. (If I had used a cap on pins 1 and 8 of the LM386 IC, I would have had 200x gain!) The MP3 player module provides very good pre-amplified sound and I did not want do meddle with with it. The car radio module cost me around 500; the pull box was 70 and rest of the parts (accessories not included) should have been less than 100.

UPDATE 1 (20-October-2013)
Front Panel Stereo Input/Output Connectors
I went to Chennai and got 3.5mm stereo panel jack connectors. I added two of them – one for audio input and another for output. I also added a switch so that the speakers are silent when the amplified signal is sent out.

By adding stereo jacks for audio input and outout, I can now send in sound output from other media players to the boombox or send out the media player’s sound output to external speakers or headphones.

By adding stereo jacks for audio input and outout, I can now send in sound output from other media players to the boombox or send out the media player’s sound output to external speakers or headphones.

UPDATE 2 (23 October 2013)
Powered Microphone
Now that I have a line input, I decide to create a powered mike with an electret microphone.

The amplifier provides only 20x gain. It seems to be too late to add 200x gain with a 10uF cap between 1 and 8 pins of the LM386 IC.

The amplifier provides only 20x gain. It seems to be too late to add 200x gain with a 10uF cap between 1 and 8 pins of the LM386 IC.

When combined with my 200x-gain LM386 speaker-in-a-box, the microphone becomes extra sensitive and can be held at a foot or two away for regular use.

A short cable between the microphone and the speaker will create a feedback loop. I use a longer cable as the speaker-in-a-box has 200x gain.

A short cable between the microphone and the speaker will create a feedback loop. I use a longer cable as the speaker-in-a-box has 200x gain.

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