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Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

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  • Class D amplifier module test PAM8403 5V 2x3W - hit or kit?
    The PAM8403 amplifier, as described on the auction site, works in class D, which suggests energy saving, while the 5V power supply and 2x3W power allows it to be powered from e.g. a power bank. You can find the modules by searching for the phrase in stores and auction portals PAM8403 . 2x3W power should be sufficient for small portable audio devices.
    After connecting 8 Ohm 10W speakers and powering the system, there was a low noise in the speakers (despite the lack of an input signal). Without connected speakers, the system consumed 5mA, after connecting 8om speakers, the power consumption increased to 13mA (without input signal). The listening test was successful, the sound was acceptable, but slightly different than from the "analog" amplifier in the AB class.

    My musical hearing is rather digital (I recognize when there is or no music :) ), and the subject of audio is foreign to me, I focused on the performance and properties of the PAM8403. I envisioned the class D amplifier as a properly controlled "buck converter" and was surprised by the lack of inductance on the amplifier module board. I count on comments and suggestions from people dealing with audio topics.

    Instead of speakers, I connected 8om resistors and here is a big surprise, power consumption increased to 132mA!
    Connecting the 4om resistors resulted in a current consumption of 152mA.
    Apparently, loudspeaker inductance plays an important role in the performance of an amplifier.
    Ultimately, the tests took place after connecting 4om resistors to the amplifier output.
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    After checking with an oscilloscope what is happening at the output of the amplifier in the absence of a signal, it was explained why there is low noise in the speakers. A waveform with a frequency of several hundred kHz is visible.
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    We feed the input of the amplifier with a sinusoidal signal 1kHz 100mVpp, the output is a modulated waveform of high frequency:
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit? Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    Connecting a loudspeaker instead of a resistor changes the shape of the output waveform:
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    The subject of audio is strange to me, but this is not how I imagined the operation of a high-efficiency amplifier. Does every class D amplifier produce such "chaff" at the output? Does PAM8403 work in class D?

    Let's compare the operating characteristics of the PAM8403 with another class D amplifier TDA8932 .
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    The first attempt, the module with TDA8932, in the absence of an input signal, consumes 46mA invariably, regardless of whether the output is connected to a loudspeaker 8om or a resistor 8om or 4om. The inductances are visible on the PCB.



    Let's give the sine at the input and at the output we get the expected sine wave instead of the "chaff":
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    The trial with TDA8932 brought me out of the shock of PAM8403 :)

    TDA8932 was powered by 15V, drawing 0.852A at an output voltage of 9.40V at a resistance of 8ohm (simulating a loudspeaker). 1kHz sine wave at the input.
    You can estimate the power supplied to the amplifier: ~ 12.78W, the output is ~ 11.05W i.e. efficiency ~ 86% .

    We return to PAM8403 with a similar test and 5V power supply connected with 4ohm resistors. The results will probably be distorted as the amplifier expects a loudspeaker to be connected, but let's see what we get. In addition, it is difficult to say what measurement error will be introduced by the multimeter, with such "chaff" at the output of the RMS amplifier may not work properly.

    With an output voltage of 1V, we get 2x0.25W, i.e. a total output power of 0.5W,
    the supplied power per input is 5V * 0.327A = 1.635W, which gives an efficiency of ~ 30%.

    With an output voltage of 2V, we get a total output power of 2W,
    the supplied power to the input is 5V * 0.711A = 3.555W, which is ~ 56% efficiency, the system is warm.

    With an output voltage of 3V, we get a total output power of 4.5W,
    the supplied power to the input is 5V * 1.273A = 6.365W which gives the efficiency ~ 71%, the system is very warm.

    When we exaggerate with the amplitude of the input signal, we get the following waveform at the output and probably quite a lot of distortion:
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    When comparing PAM8403 with TDA8932, the output waveforms and the behavior of the circuit are different. The price of PAM8403 modules is low and perhaps in simple devices with speakers such an amplifier is sufficient. The sound obtained from the PAM8403 is acceptable (for me) and in many devices it will be a good solution.

    What do you think about the PAM8403 amplifier, hit or kit?

    A request for feedback from people knowledgeable in audio issues and having appropriate hearing (if they had the opportunity to listen to the effects of similar amplifiers).

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  • #2
    krisRaba
    Level 31  
    The big difference is that there is no output filter on the PAM board. At first glance, you can see that the TDA has chokes and filtering capacitors, and the PAM has the pins of the IC connected directly. Without filtration, it is rather difficult not to see and hear this light chaff ;) If the TDA filters were shaved off, it would probably not be crazy ;)
    These PAM tiles are quite minimalistic, but I was surprised that they can sound pretty well anyway (you know, a relative concept, but there's no tragedy).
    I used to make an output amplifier on some 12V PAM and after adding some components to the minimalist version it sounded quite nice. It is not HiFi, but you can listen :) However, you have to be careful about power supply, etc. It is better to get to these PAMs with the application note than the catalog note, because it contains a lot of tricks and "how-to", which we will not see in the datasheet ;) It cost me the need to develop a v2 version of the board to get rid of the squeaking ;)
  • #3
    TechEkspert
    Editor
    Soon I will put a test of the older brother of this module, i.e. PAM8610 (15V 2x10W), we will see what features it has.
  • #4
    katakrowa
    Level 22  
    I also have 2 of these modules. And after the first connection, I saw 100khz chaff on the oscilloscope ... I didn't have as much patience as you did to analyze it deeper.
    Generally, these modules are not designed for listening to music, given their ridiculous price and small size, they can be a great solution for devices such as:
    - talking elevator informing which floor you are on;
    - an amplifier of information signals in some machine;
    - other applications for various controllers, alarms;
    - maybe also active speakers at stations in churches, etc ...
  • #5
    398216 UsuniÍty
    Level 43  
    It seems to me that the speaker inductance plays the role of the filter. This would explain the noise at the output without a signal, and the increased current draw after replacing the loudspeaker with a resistor.
    This is an amplifier (in class D, but ... simply simple to the point of absurdity) of low power, for typically "portable" applications, and in such speaker sets the speakers themselves have the quality ... let's say "average". So there is no point in expecting some super-quality, perfect lack of noise (clock frequency) on the output, etc. This is supposed to work and additionally be cheap and economical in power consumption. And is...

    Added after 2 [minutes]:

    PS A similar "chaff" can also be observed in the speaker outputs of amplifiers from some cheaper (but not only ...) towers with D amplifiers. Maybe a bit lower amplitude (because the manufacturer adds some simple filters for the outputs), but still.
  • #6
    linx
    Level 21  
    I have been using a similar module for over a year in USB DIY speakers. The loudspeaker inductance acts as a filter in this circuit. I consider the quality to be satisfactory, the system works properly from a voltage of 3V3 (I have not tested at the lower one). The version with a potentiometer is also noteworthy, and it has a filter capacitor on it.

    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?
    Source: AliExpress
  • #7
    398216 UsuniÍty
    Level 43  
    linx wrote:
    there is also a version with a potentiometer, which also has a filter capacitor.
    Yes. Filtering but supply voltage.
  • #8
    linx
    Level 21  
    398216 UsuniÍty wrote:
    linx wrote:
    there is also a version with a potentiometer, which also has a filter capacitor.
    Yes. Filtering but supply voltage.


    That was exactly what I meant too. The manufacturer PAM8403 boasts that the system works FILTERLESS, but in order to reduce EMI interference, he recommends an output filter.
  • #9
    Marek_Ertew
    Level 16  
    Typical D-type amplifiers work in PWM modulation. Circuits from the PAM family have the proprietary PAM modulation. Datashit does not explain what it is about, but even without an oscilloscope you can notice that these amplifiers work differently from typical representatives of the genre.
  • #10
    TechEkspert
    Editor
    I checked PAM8610 , in short, more power, more noise, but the power consumption is less dependent on the inductance of the connected receiver.
  • #11
    irek2
    Level 40  
    Quote:
    Typical D-type amplifiers work in PWM modulation. Circuits from the PAM family have the proprietary PAM modulation. Datashit does not explain what it is about, but even without an oscilloscope you can notice that these amplifiers work differently from typical representatives of the genre.


    What do you mean when writing typical class D amplifiers? Probably not the nonsense that they write in the books that a class D amplifier is a comparator comparing a triangle waveform with an audio waveform !? This is just a simple attempt to explain how it works.

    All class D amplifiers operate on the principle of PWM modulation! And there are endless ways to implement it.

    In systems without an output filter, two offset modulators are used, which in the rest state on the loudspeaker give a pin-like voltage that grows with the output power. It's no big deal just the difference between the two classic PWM tones.
    In order not to exceed the noise emission standards, the loudspeaker to such an amplifier should be connected with a cable of a few centimeters at most.

    Each amplifier in the D kalsa has a "muck" RF output at the output. but that has nothing to do with audible noise. These are measured by a special RF cut-out filter.

    To sum up, this test is weak, since the tester himself admits that he has no idea about audio technology :)
  • #12
    TechEkspert
    Editor
    If someone wants to describe his tests on the electrode and has an idea for a sensible use of the system, the possibility of testing, or want to get acquainted with this type of amplifier, I have 3 pcs such PAM8403 modules to be made available in exchange for describing your trials.

    It is also possible to share 1 piece PAM8610: https://www.elektroda.pl/rtvforum/topic3458321.html for a similar purpose.

    First come first served.
  • #13
    gradek83
    Level 41  
    Recently, I was just thinking about using this amplifier for a mini panel FM AUX USB BT MP3 etc and make a portable speaker. While browsing, I found an interesting blog where someone already took it up and even took care of the mentioned interference and the EMI filter.
    LINK
  • #14
    irek2
    Level 40  
    You can buy a ready-made player module with plugs on board, so why bother?

    What could be interesting in this article if no filter is needed !?

    The genius of this solution lies precisely in the fact that the system does not require large and expensive chokes!
  • #15
    jestan
    Level 11  
    Hello

    I bought a BT module with this amplifier
    Class D amplifier module test PAM8403 5V 2x3W - hit or kit?

    It connects, plays for about a minute and begins to break off gradually until the connection is completely broken. Interestingly, keeping your finger on the "mass" (USB socket) works all the time.

    Any suggestions???
  • #16
    gradek83
    Level 41  
    jestan wrote:
    Any suggestions???

    Power module 5V, not 3.7V Or use a STEP UP 5V 1.2A converter