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Why does my LM386N-1 amplifier chip get hot when using mp3 player as input, but is fine when guitar is the input source?


I made the amplifier in this instructable http://www.instructables.com/id/Make-a-Sweet-Portable-Guitar-Amp/ and it is currently in breadboard stage. I had a few problems after adapting the circuit to have a switched dc input jack as well as battery. But after some trouble shooting i fixed these errors.

I ran it off battery and dc input (9v) wall adapter (a universal 500mA regulated ac/dc transformer set to 9V) with a guitar as the input and it worked fine (as far as i know).

Then as it said in the instructable that you could use it with and ipod or mp3 input too, i thought i'd try it and see what it was like. I used the dc input adapter when i did this and plugged in my mp3 into the input jack using a 3.5mm to 1/4" adapter. Then when i swithced on the circuit i didn't hear my music through the speaker, just a bit of hum and then i smelled a slight electrical burny smell so i turned off the power as quickly as i could. Then i felt around and it was the lm386n-1 chip that was getting hot.

Firstly can anybody diagnose the problem?

Secondly, is it likely to have permanently damaged my chip?

Thirdly, do you think it will be because of the power source not being a battery? I don't think so, it worked fine with both with guitar input. But i suppose it could be related to that

dog digger2 years ago
Ipods amp MP3 are very powerfull devices in term of output power compared to a guitar. but it depends on how high the output of the MP3 or IPod was. If it was like a 1/10 of the volume avalable on the MP3, the amp should be fine but I think you have a dead chip
Without reviewing your actual circuit in detail, I'd lay very good odds you have a weird connection to your power supply. Was the Ipod on wall power too ?

Steve
mdog93 (author)  steveastrouk3 years ago
I think i had the polarity of the dc power supply the wrong way round, even though i checked i had it right.

I checked i had it right, but must have been confused about which way WAS right for my circuit. So i must have burnt out the chip. I swapped it for another one and it seems to work fine again...
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