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Anyone use an LM386 to drive speakers on 5v?



  • My next build is a palmtop, and I'm thinking about using a pair of LM386 as audio amps.
    According to the chip's datasheet, you CAN power it from 5V, It looks ideal to amplify the output from the 3.5mm plug on the Pi 3 B to 8 ohm speakers, but thought I would ask if anyone has actually tried it.

    Also looking for tiny 8ohm speakers to use it with, any ideas?



  • @victimrlsh I do not recommend this option. You should either hack some old stereo speakers - this is what I did here or buy a decent kit with something like a TDA2050 or similar. There are many problems with the LM386 in my experience. First, they need a large amount bypass capacitors to remove unwanted noise from killing your performance and even then it will not be great. You will need a 100uF electrolytic cap in parallel with something like a 0.1uF ceramic across the supply rails (close to the chip). These will help short circuit unwanted AC noise away from the chip. One will deal with the high frequencies and the other with low frequency noise. The next is choosing to run at 5V which is at the minimum. For this, you will be needing even bigger (470uF to 1000uf) supply bypass capacitors to stop the supply voltage from jumping up and down with the output signal. The jumping creates a motorboat sound. Volume at this voltage will be low. 9V would be better and 12V better still but then it gets hot! For me, these are only really good as a pre-amp for something like a microphone. For speakers, I use these ones.



  • @victimrlsh MAX98357 I2S is a good choice



  • @cyperghost I'll probably go that route, Lady Ada's stuff hasn't let me down yet.



  • Just looked in my parts cabinet, I have 17 LM386's, so I'm going to build this to see how it works anyway. I'm still going to get that Adafruit module though, that looks sweet.

    @rbaker Those options are way too big for a palmtop config. I have some pretty tiny caps, maybe even some axial mount to keep the size down.



  • @victimrlsh Palmtop! Missed that! I agree!



  • @rbaker Breadboarded the circuit. The only problem was the 10uF cap to boost the gain to 200x, as you can see in the pic, I have its lead pulled. High distortion with that in place and no appreciable gain in volume. The 20x native to the LM386 gives the same volume as a GBA (seen here running Advance Wars from my prototype controller mounted build) running from a 6v supply. The audio quality is about the same as a GBA as well. Nothing incredible, but adequate and I should be able to cram a couple of these in that casing without a problem.

    0_1540689820822_LM386amp.jpg

    0_1540689847896_Audio2.jpg


 

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