Class D Audio Amp (from China)

Discussion in 'General Electronics Chat' started by tracecom, Oct 9, 2012.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    Attached is a photo of a class D audio amp I just received. Here are the advertised specs.

    Description:

    Work: D Class
    Quiescent Current: 20mA
    Efficiency: 90%
    Rated output power: 10W +10 W (8Ω)
    Frequency response: 20Hz to 50KHz
    Operating voltage: DC7.5-15V
    Recommended supply voltage: 12V, the center PIN of 12VDC is +.
    PCB board size: (40 * 40) mm

    I have tried it and it sounds really good to my untrained (and abused) ears. Using a 9V power source (6AA cells) and two 4-inch, 8Ω, 10W (Pioneer) speakers, it draws only ≈25mA at a comfortable listening level. Wide open, it is uncomfortably loud. I paid $6.98 including shipping.

    This seems like a mixed blessing. I like the amp, but the good performance and low price discourage me from trying to build one. In addition, the relatively high number of SMD parts is a further deterrent to my initiative.
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    Somebody else posted more details about this Chinese class-D amplifier.
    Its output is phoney-baloney 10W PEAK per channel into 8 ohms when its supply voltage is 12V.

    With a 12V supply its output at clipping is only about 4W RMS per channel into 8 ohms.
     
    smokingwheels likes this.
  3. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I "won" this one last night on ebay for $3.20C (including shipping,) but I haven't received it yet.
     
  4. Audioguru

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    Dec 20, 2007
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    Its datasheet shows that with a 5V supply (its maximum allowed supply is 6V but it might get too hot) it begins to clip when its output power is only 2W into 4 ohms or is 1.2W into 8 ohms, like a cheap clock radio.
     
  5. tracecom

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    Apr 16, 2010
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    You love to say that! :)
     
  6. Audioguru

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    I bought two Name Brand clock radios at a surplus store for $1.75 Canadian each! They sound AWFUL!
    They pickup only very strong local FM stations. Their clocks work well.

    I souped up a GE clock radio about 30 years ago. I built a low distortion amplifier with an LM390 IC and replaced its 3" lightweight speaker with one that has a huge and heavy magnet.
    I made a bass boost circuit that boosted low frequencies 20dB and it sounds great. The bass boost circuit senses the volume control position so full boost occurs when the volume is low and no boost when the volume is high.

    It still works today but the 30 years of running the LED display dimmed it so it cannot be seen properly in daylight.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    I bought two Name Brand clock radios at a surplus store for $1.75 Canadian each! They sound AWFUL!
    They pickup only very strong local FM stations. But their clocks work well.

    I souped up a GE clock radio about 30 years ago. I built a low distortion amplifier with an LM390 IC and replaced its 3" lightweight speaker with one that has a huge and heavy magnet.
    I made a bass boost circuit that boosted low frequencies 20dB and it sounds great. The bass boost circuit senses the volume control position so full boost occurs when the volume is low and no boost when the volume is high.

    It still works today but the 30 years of running the LED display dimmed it so it cannot be seen properly in daylight.
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I took the amps and speakers out of two clock radios, and built them into a cabinet to make a top-end Hi-Fi stereo sound system! It sounds fantastic!

    Just kidding, Audioguru is right; clock radios are bad. ;)

    Thanks Tracecom for the quick review of the stereo high efficiency class-D amp module from ebay. That sounds like a great amp for a battery powered guitar amp project. Good to see it only draws 25mA at a "comfortable listening level"!

    I think it's pretty impressive these new digital amps that run off the same power used by an old LED, and even more so that you can buy them for $6.98 including shipping!
     
  9. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    The problem is that it's stereo. Is there a good workaround for that?

    They're still available, but they have gone up a buck or two.
     
    Last edited: Oct 10, 2012
  10. Sensacell

    Well-Known Member

    Jun 19, 2012
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    What is freaking me out is that there are no inductors on the board?
    Speaker inductance only?

    Must be an EMI nightmare!

    Long speaker cables = more EMI.

    The amp is massive! where would you put it?
     
  11. Audioguru

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    The manufacturer says that the amplifier is filterless. But something is cutting high frequencies because the frequency response rolls off above 10kHz.
    Yes, the datasheet says that you probably want to use LC filters on each output.
     
  12. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    That's a joke...right? :)
     
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