PAM8403 Amplifier Distortion Problem In PC even at Very low volume and No Bass

Discussion in 'General Electronics Chat' started by Vipul Kumar 1, Mar 2, 2019.

  1. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    PAM8403 Super Mini Digital Amplifier Board 2 * 3W Class D Digital 2.5V To 5V Power Amplifier Board Efficient
    https://www.aliexpress.com/item/PAM...lgo_pvid=b10f451e-ec2e-4f0e-813b-56cacb30404b
    actually i purchased this board from above link i hv connected this amplifier with 5v power supply with 2 3W 4ohms speaker but it is giving too much distortion when i am using it with pc or laptop wheven i am increasing volume above 10% it starts getting distorted but when i am connecting it with mobile phone it is giving excellent sound with good bass
    one more thing no bass when using it with pc or laptop is there any one who can help me with this amplifier module
    how can fix this issue????
     
  2. sghioto

    Well-Known Member

    Dec 31, 2017
    1,039
    157
    How are you connecting it to the computer? What output jack on the laptop or PC are you using?
    SG
     
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  3. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    Power given through usb and 3.5 mm jack used for output
     
  4. sghioto

    Well-Known Member

    Dec 31, 2017
    1,039
    157
    How are you powering the amp when connected to the phone?
    SG
     
    Vipul Kumar 1 likes this.
  5. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    Same way using usb
     
  6. sghioto

    Well-Known Member

    Dec 31, 2017
    1,039
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    Have you tried a different PC?
    SG
     
    Vipul Kumar 1 likes this.
  7. MrSoftware

    Senior Member

    Oct 29, 2013
    1,331
    407
    I had a similar problem with a couple of audio amplifier chips recently. I believe your problem is the impedance of your speakers is too low and the amp is clipping horribly, or the over current protection is cutting the output. In my case the specs on paper did not pan out in the real world, and I ended up running much higher impedance than the spec specified, and got much better results. Put your two speakers in series instead of parallel, to get an 8ohm static impedance. See if that makes an improvement.

    Edit --> I just re-read your post and maybe I'm wrong. Use a scope to look at the input signal from the PC and from the phone, try to play a single frequency test tone, maybe 1kHz. See if you notice any difference.
     
  8. bertus

    Administrator

    Apr 5, 2008
    19,408
    3,924
    Hello,

    According to the datasheet 4 Ohm speakers can be used.

    PAM8403_output power.png

    As you can see the distortion will rise at high volume.

    Bertus
     
  9. Yaakov

    Well-Known Member

    Jan 27, 2019
    1,369
    670
    This sounds like an input impedance problem. Or, possibly, badly wired connectors.
     
  10. bertus

    Administrator

    Apr 5, 2008
    19,408
    3,924
    Hello,

    Are you using the headphone output of the PC and phone?
    Then you might have a to high input voltage for the amplifier causing the distortion.
    What happens when you lower the output volume of the PC or phone?

    Bertus
     
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  11. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    Are you using the headphone output of the PC and phone?(Yes)
    Then you might have a to high input voltage for the amplifier causing the distortion.
    What happens when you lower the output volume of the PC or phone?(when lowering the output volume in pc sound become less at 10% sound is little ok increasing over 10% of the volume giving very bad distortion but no problem with phone giving decent output even at full volume
     
  12. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    yes i hv tried with different pcs and laptops same problem
     
  13. bertus

    Administrator

    Apr 5, 2008
    19,408
    3,924
    Hello,

    You could try this little attenuator between the PC and PAM amplifier:
    PC to PAM.png

    The PC will see a 33 Ohms load (close to the usual impedance of a headphone) and the pam will have an attenuated signal.

    Bertus
     
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  14. Vipul Kumar 1

    Thread Starter Member

    Oct 20, 2018
    43
    1
    actually i did not understood this circuit??/
     
  15. bertus

    Administrator

    Apr 5, 2008
    19,408
    3,924
    Hello,

    What do you not understand from my circuit?

    The 33 Ohms resistor provides a load for the PC output.
    The ouput of the PC may be distorted when no load is connected, due to impedance mismatch.
    The other two resistors will attenuate the signal by a factor of about 3 times.

    Bertus
     
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