Based on an original diagram by Middlesex University Teaching Resources Unit (www.mutr.co.uk), modified by Mark Cottle to incorporate aspects of circuits designed by Beavis Audio and runoffgroove.com. This is the circuit in my Cohiba cigar box amp.
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C5 blocks any DC from going to the output.
C4 and R3 are an "RC filter" which helps to stablise the circuit (according to the Runoffgroove article on the Little Gem)
The connection from pin 7 of the LM386 to ground via C2 is described in datasheets and schematics as "bypass" - I'm told it removes "AC noise" or hum and also makes the circuit more stable.
That's about the limit of my ability to explain these things. I have a basic understanding of electronics but I'm not an electronics engineer and I depend greatly on others when it comes to the arcane subtleties of amplifier design. So I can't give you the full technical spiel on what is meant by stability. However, I can say from experience that weird things can sometimes happen with amp circuits. Some of my early construction attempts suffered from a tendency to turn into oscillators. Putting in the stuff in the bottom right corner and also C1 definitely made a difference.
Thanks for that link Michael, it has set me off in some new directions and has re-kindled my ambition to (one day) build a battery powered minature tube.
Beavis Audio (www.beavisaudio.com) and Runoffgroove (www.runoffgroove.com) have some designs for slightly more elaborate LM386 circuits with tone controls of one sort or another. While you could certainly try incorporating some of the tone stacks described in the article Michael has posted, the Beavis and Runoffgroove circuits are tried and tested designs for complete amps.
The lm386 has a gain control built in, all you have to do is put a pot on it. I'm not sure how you would do it in other amps. here is a good article for tone controls - http://amps.zugster.net/articles/tone-stacks
Hi, I'm wondering how easy it is to add tone and gain control to an amp?...is there anywhere that explains it in idiots terms, I don't understand diagrams and schematics : -/
Comments
C4 and R3 are an "RC filter" which helps to stablise the circuit (according to the Runoffgroove article on the Little Gem)
The connection from pin 7 of the LM386 to ground via C2 is described in datasheets and schematics as "bypass" - I'm told it removes "AC noise" or hum and also makes the circuit more stable.
That's about the limit of my ability to explain these things. I have a basic understanding of electronics but I'm not an electronics engineer and I depend greatly on others when it comes to the arcane subtleties of amplifier design. So I can't give you the full technical spiel on what is meant by stability. However, I can say from experience that weird things can sometimes happen with amp circuits. Some of my early construction attempts suffered from a tendency to turn into oscillators. Putting in the stuff in the bottom right corner and also C1 definitely made a difference.
Beavis Audio (www.beavisaudio.com) and Runoffgroove (www.runoffgroove.com) have some designs for slightly more elaborate LM386 circuits with tone controls of one sort or another. While you could certainly try incorporating some of the tone stacks described in the article Michael has posted, the Beavis and Runoffgroove circuits are tried and tested designs for complete amps.