Connect with us

What Is Happening Here?

Discussion in 'General Electronics Discussion' started by gibon0695, Jul 27, 2016.

  1. gibon0695

    gibon0695

    27
    3
    Dec 2, 2015
    I've built an amplifier circuit.

    I hooked it up to an oscilloscope and I get this response at the lower bass frequencies, at 100% volume.

    I am only worried about this for analysis purposes. The amplifier is Class D and distortion is expected at 100% volume.

    Is this pure distortion, clipping, or is something else going on?

    Cheers

    [​IMG]
     
    Mongrel Shark likes this.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,219
    2,695
    Jan 21, 2010
    There's something wrong there. What does it look like at lower volume settings?
     
  3. gibon0695

    gibon0695

    27
    3
    Dec 2, 2015
    At around 75% volume it looks like this... it works. That image above in the OP occurs at 100% volume. What could cause this?

    As the frequency gets higher the sine wave gets better.

    I think it is caused by a lack of power at the lower bass frequencies. It does not do this at higher frequencies. Could I be right?

    [​IMG]
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,219
    2,695
    Jan 21, 2010
    Does it happen suddenly or does it progressively get worse as the volume is increased?
     
  5. shrtrnd

    shrtrnd

    3,676
    454
    Jan 15, 2010
    What part numbers are the components you're using for your amp?
    21V at 20Hz makes me wonder if this is a circuit problem, over-driving the circuit components, or maybe a limitation
    on the scope value parameters for the functions you've selected. Measurement instruments are precise, but you
    have to be aware of their limitations. Triggers/filters/ automatic functions can kick-in so that what you see on the scope isn't always what's actually there.
     
  6. Sunnysky

    Sunnysky

    465
    115
    Jul 15, 2016
    check your Vdc supply rails
    I looks like insufficient storage caps for low frequency power.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,219
    2,695
    Jan 21, 2010
    Curiously, only on one rail.

    The waveform looks like a discharging capacitor.

    I can see this happening if the demanded output voltage exceeds the supply rail and the power supply is incapable of supplying sufficient current to maintain even that lower voltage.

    However, the small class D amplifiers I've seen use a single ended power supply and what is effectively an H bridge to drive the load.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-