Electronic – How to decrease distortion/noise of LM386 amplifier at max gain and volume

amplifierdistortionlm386noise

From my previous question, I've made LM386 amplifier and it works better than LM1458 amplifier. I've added gain and bass boost in my LM386 amplifier.

  • How to decrease distortion/noise of LM386 amplifier which occurs at max gain and volume?
  • Is using pin7 which is the bypass can fix the problem?
  • Is there other way to improve my amplifier or do i lack something which can improve my amplifier?

additional questions:

  • Since i have Bass boost, how to add treble control?
  • How long can LM386 last(hours) when playing music using regulated power supply(9v)?
  • What will be the effect of using 6 ohms speaker instead of 8 ohms speaker?

Edit:

  • fixed postion of C6 and R4

Schematic diagram updated: (sorry for the mistake I've done, updated again.)

  • after changing the position of R4 and C6, I've noticed the increase in volume. But when i changed the connection of C4 from pin4 to output(pin5) bass boost doesn't work anymore and when i put the bass boost to minimum the sound turns off also even the volume is maxed, that's why i connected C4 to the pin4. Is there a way to fix it or should i still connect c4 and pin4?

schematic

simulate this circuit – Schematic created using CircuitLab

Thanks for all the comments and suggestions, and it was successful,

Best Answer

After you updated the diagram:

R4 is still in the wrong place. If you've built the circuit with R4 that way, then it is WRONG. With R4 where you have it, you lose a very large part of the volume.

Check the diagram in the LM386 datasheet and compare it to what you have built.

  1. You need to work on your circuit diagramming skills. If your circuit is built as drawn then it cannot work. Since it does work, you must have drawn the circuit wrong.
  2. Distortion is to be expected if you input a large signal with high gain. The amplifier only has 9 Volts to work with. If you put in a 1V peak to peak signal with the gain at the default of 20, then the amplifier will try to put out a signal at 20V peak to peak. Since it only has 9Volts to work with, you get a lot of distortion.
  3. C4 is not needed in most cases. If it is needed, then it probably needs to be larger.
  4. R4 is (as Steve G has already noted) in the wrong place.
  5. You've got pin4 connected as an input - it is actually the ground connection for the chip and should be connected directly to ground.

Give the number of obviously wrong things in your diagram, it would be difficult to guess what could be improved in the gain and tone control areas.

The LM386 is not rated for high power. It should be capable of making a speaker loud enough in a classroom setting (small room,) though not if you are trying to fill an auditorium with a couple of hundred students.

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