"How to build a guitar amp" 

 

Ok, So to start with at least we are going to be using the LM386/JRC386 Power amp chip because it's dirt cheap and is far and away the most popular power amp chip for DIY electronics use, particularly when it comes to guitar, and for really good reason. I've heard it said many times that the reason the 386 chip is so popular is because it's so easy to use and require few external components ..... all of which is absolute bollox. 386 chips are notoriously temperamental, they squeal like fucking banshees if you don't set them up properly and they start making making horrible motor boating noises if you even look at the power filter cap funny. They also require quite a few external components to stabilize them and get them sounding at their best. They do however have one massive ace up their sleeve, and that is that they overdrive really well. Most power amp chips clip like smashed class being scraped down a gravel drive so the conventional way to use them is to use a pre-amp (basically an Overdrive/Distortion pedal) circuit  to shape the sound and create the clipping, and then use the power amp to cleanly amplify the resulting signal and provide enough power to drive a speaker. That's all gravy when you are using a 10 or 20 watt Solid state practice amp plugged into the mains but when you are dealing with 1 watt running on a 9v battery there isn't exactly a lot of clean headroom available so as soon as you start cranking the volume the power amps going to start to clip and that's when things get nasty. 

 

 

 



The beauty of the 386 chip is that it overloads gracefully like the power amp section of tube amp or at the very least a decent overdrive pedal. This is awesome for 2 reasons, 1) you can really crank the volume and milk every last drop from that 1 watt of power without it sounding like pebble dashed dogshit  and 2) you don't need any complicated pre-amp circuit to create the clipping, you can just overload the input and the chip will take care of the rest. 

 

 

                

                 

 

  • Inverting / Non inverting input  
  • Don't buy Cheap/fake
  • Comes in 1,2,3,4 and A,B,C,D - LM386 4/D = 1w

 

 

 

 

 

 

The Smokey