Audio Amp question - Audio clicking and player resets.

[4kruby]

Hello,

I got a cheap MP3 decoder board which plays MP3 from an SD card.
Precisely this one : https://robu.in/product/gpd2846a-tf-card-mp3-decoder-board-2w-amplifier-module/

I powered this one with a lithium battery (3.9v) and boosting the voltage to 5v with a boost converter : https://robu.in/product/mt3608-2a-max-dc-dc-step-power-module-booster-power-module/

And using a 8Ohm 5W speaker. (the onboard Audio amp of the mp3 decoder board has 2W amp).

At lower volumes, it works fine. However, If I increase the volume (the volume control is in the same module), the song stops and there is a continuous crackling sound for a second or two and the module resets.

I tested the current draw (50  to 80mA) and voltage(4.9 to 5V) which are well within limits of the power source (I did a very coarse measurement with a DMM).

So, where is the problem with this? Should i drive it directly from the battery (removing the boost circuit in between)? Or is there problem with using a higher rated speaker?

Thanks

[bob91343]

I suspect the boost circuit.

[4kruby]

Hello,
Thanks for your response.

But even after removing the boost circuit, the same thing happens. However, on particular occasions, it played fine:

Basically this is my setup :
I am not soldering anything here, Just using alligator clip wires (end to end alligator clips) to connect them. Lithium cell to protection circuit, protection circuit to boost circuit, and then to multimeter (for current measurement), multimeter to MP3 decoder board and finally to speaker. Here, after the lithium cell protection circuit, all components are connected by alligator clip wires.

1. The above circuit is fine for low volume, however for moderate to high volume, the music stops (with a trrr sound from speaker and the module resets) - this just precisely loops.
2. If I remove boost circuit from the above, the behavior is the same.
3. After removing boost circuit, if I connect another 8 ohm speaker in series, it works fine for high volume
4. If I add boost circuit with two speakers in series, again the same behavior - music stops with speaker chatter and module resets.
5. If i shorten the wires, - remove the multimeter inbetween, then it works fine with boost circuit.

So, from the above experiments, I came to a conclusion that the alligator clip wires are some how causing the problem. So, I measured their resistance - it was surprisingly high (0.8 to 0.9 ohms). So, shortening the wires proved to be useful. Do any one has any other insight into this topic?

Thanks.

[bob91343]

It may be an oscillation caused by the inductance of the clip leads.  Shorten all the connections and see what happens.

[4kruby]

Hello,
Thanks. Yes, I soldered all the wires and tried, it works perfectly with a single speaker to the output (8ohms 5w) and with the boost circuit.

So, the problem is with using the jumper wires with alligator clips. Honestly I would have never suspected them. But this is interesting as to how they cause this kind of disturbances. Can any one point to any resources on this subject? or is it general audio?

Thanks.