Small Loudspeaker for Computer or Cell Phone

Published  September 19, 2015   28
J Jayant
Audio Amplifier: Small Loudspeaker for Computer or Cell Phone

Small Loudspeaker is a fun project to do, you can connect it to your Cellphone or Laptop through a 3.5mm audio jack and can enjoy your own loudspeaker. You can also connect it to any device which has a 3.5 mm audio output, like TV, music player, video games etc. We have used LM386 IC to amplify sound, with a few external components.


LM386 is a low voltage audio amplifier and frequently used in battery powered music devices like radios, guitars, toys etc. The gain range is 20 to 200, gain is internally set to 20 (without using external component) but can be increased to 200 by using resistor and capacitor between PIN 1 and 8, or just with a capacitor. Voltage gain simply means that Voltage out is 200 times the Voltage IN. LM386 has a wide supply voltage range 4-12v. Below is the Pin diagram of LM386:

LM386 Pinout

Pin description of LM386 along with the functions of external components used for amplification:

PIN 1 and 8: These are the gain control PINs, internally the gain is set to 20 but it can be increased up to 200 by using a capacitor between PIN 1 and 8. We have used 10uF capacitor C1 to get the highest gain i.e. 200. Gain can be adjusted to any value between 20 to 200 by using proper capacitor.

Pin 2 and 3: These are the input PINs for sound signals. Pin 2 is the negative input terminal, connected to the ground. Pin 3 is the positive input terminal, in which sound signal is fed to be amplified. We have connected one terminal of 3.5 audio jack to this input PIN 3 and the other terminal to Ground. 3.5 mm Pin is further connected to the Laptop’s audio jack.

3.5 mm stereo audio jack is found in mostly headphones, there are generally two types 3.5 mm audio Jack, TRS (TIP RING SLEEVE) and TRRS (TIP RING RING SLEEVE). In TRRS one extra terminal is generally for Microphone. We have used TRS audio jack here and soldered two wire to it, one to Ground (Sleeve) and other to Right audio (Ring) . You can understand by below images:

  TRS and TRSS Audio Plug

Pin 4 and 6: These are the power supply Pins of IC, Pin 6 for is +Vcc and Pin 4 is Ground. The circuit can be powered with voltage between 5-12v.

Pin 5: This is the output PIN, from which we get the amplified sound signal.

The output signal has both AC and DC component, and DC component is undesirable and can’t be fed to Speaker. So to remove this DC component, a capacitor C2 of 220uF has been used.

Along with this capacitor, a filter circuit of Capacitor C3 (.05uF) and resistor R1 (10k) has been used at the output PIN 5. This filter also called the “Zobel network”, this electronic filter is used to remove the sudden High frequency oscillations or noise.

Pin 7: This is the bypass terminal. It can be left open or can be grounded using a capacitor for stability.



  • IC LM386
  • 3.5 mm audio Jack
  • Speaker 8ohm
  • Capacitors- 220uF, 10uF (two), 0.05uF
  • Resistor- 10k
  • Battery 5-12v


Circuit Diagram and Explanation

Small Loudspeaker Circuit Diagram

I have cut the male to male 3.5 mm audio jack and solder two wires, but one should a female 3.5 mm audio jack for bread board. And connect one end of male to male audio jack to female audio jack and other end to computer.


This circuit is quite similar to my previous circuit “LM386 Based Audio Amplifier Circuit”, we just replaced the Condenser Mic with the 3.5 mm audio jack to provide the input sound. Also potentiometer has been removed, because there is already a sound control in computer’s Music player.

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Submitted by Bhem on Sat, 02/06/2016 - 08:55


Do you have the computations on how you arrive to those values of capacitors and the resistor?

Submitted by lee on Tue, 05/03/2016 - 01:01


where should the positive and negative terminal connect...

Submitted by jitesh on Wed, 05/18/2016 - 15:43


ic 810 audio and lm386 audio campers are the which is the best tell me please

Submitted by Leo Cheng on Sat, 05/28/2016 - 20:46


Hello Jayant . I followed your steps, and everything seemed OK. My audio is from raspberry pi A+ 3.5mm jack, but the noise is very loud. Could you give me any suggestion to remove noise?

Submitted by S.saravanan on Mon, 05/30/2016 - 11:27


Sir, anyone tell how to play song from USB readed SD card connection with 3.5mm jack ..output two speaker...which ic I choose?.. Please describe

Submitted by Rahul on Sat, 07/30/2016 - 22:13


Can i make this using transistor bc548 instead of Ic?

Submitted by Rohan on Thu, 08/11/2016 - 15:56


It's very useful. I try to made it. connection was okk bt get the output very low. how it is increase??? plz give me suggetions..

Submitted by dea on Tue, 09/13/2016 - 07:22


hi. were doing this for project and i'm just wondering if you could tell me whats the power range of the three capacitors. because the shop is asking for volts..

Submitted by sushil sharma on Wed, 10/19/2016 - 21:04


I have make this project in ccb(copper circuit board) ..this circuit works well but the sound quality is not good..In this circuit nothing is used for voice cancellation...

Submitted by Simran Bisht on Mon, 02/06/2017 - 20:56


as i am using high pass filter at the input . so i want to confirm that positive output terminal of high pass filter should be connected to pin3 of lm386 and the negative terminal should be grounded !! am i right ?? or any further connections are needed ?? plzz tell