Tag Archives: lm380

LM380 2W Samsonite suitcase guitar amplifier

I built this amplifier using the LM380N IC. It was an easy amp to build, but I used a Radio Shack circuit board to do some tinkering. I wanted to have a switchable transistor boost pre-amp, but without using a 3PDT switch and true bypass, I couldn’t think of a way to do it without making the whole thing unusable.

I settled for a clean, 2W amp. The great thing is that it can be used with effects pedals to achieve any sound that could be desired. One aspect of the LM380 chip is the input voltage. The maximum input is 100mVp-p, which has been observed by using a standard electric guitar. The input voltage is reduced using a voltage divider consisting of a simple potentiometer. I soldered the pot directly to the input jack and took the output to the circuit from the wiper. This gives the end user complete control over the amp. Hotter guitars will need to be trimmed down, and hobby guitars built with Cigar boxes can be trimmed up, if needed. I set the amp to work with a Tele-style guitar to work with minimum noise.

This is a springboard project. Version 2.0 is in the works to have distortion capability. I want to have the LM386 as the pre-amp and the LM380 as the power amp. This same circuit will also become the basis of future Cigar Box Amps.

2W amplifier schematic [Version 1.0 - Scrapped]
2W amplifier Schematic [Version 1.1 - added trim pot/removed input cap]