PAM8403 Amplifier Bluetooth Speaker: Tackling 'Tickling' Sound & Mass Loop Issues

Hello,
I recently made a bluetooth speaker on the PAM8403 amplifier. Unfortunately .. there is a problem, namely with "tickling" speakers (I don't know how to describe it otherwise). I thought I was getting a "Mass Loop" so I modified the circuit in all sorts of ways. I have no idea what the reason is, that's why I'm writing here.

Below I present a short video of how it all works after switching on. Unfortunately, I cannot record how the loudspeaker sounds, because it will disconnect my music while recording.

[movie: a37dc16403] https://filmy.elektroda.pl/19_1501749043.mp4 [/ movie: a37dc16403]

this amplifier is unfortunately like that .... bridge the input with a resistor, e.g. 10K and see /

Hello,
I suggest you to familiarize yourself with the catalog data of this system.
You didn't include the schematic, but the image emerging from the video shows you may have a problem with the power supply.

greetings

@Nothing
- The resistors did not help, and I have the impression that it is starting to twitter more. Instead of a relatively light sound "trr yyy yy" there's a little louder "prr yy", however it sounds.

@krzysiek_krm
- The PAM8403 amplifier is powered by two Samsung cells:
Full name: AkumuIator 18650 ICR18650-26H Samsung 2.6Ah Li-Ion

As for the scheme, it looks like this:


Added after 13 [minutes]:

After desoldering the resistors, the speaker still squeaks.

Added after 1 [minutes]:

I guess it could be either BT's or Jack's fault.

The amplifier needs a 5V power supply.

What should I power it with? Should I walk on my back with the battery? :P

Added after 44 [minutes]:

When I connected the akku in series, BT is supposed to be powered, because the diode is flashing, but the speakers are not playing.

Added after 5 [minutes]:

And when I touched the amplifier's akku, it was terribly hot. With a parallel connection, xd was not so

rnb_bolii wrote:

The amplifier needs a 5V power supply.

Not necessarily, the documentation of the system shows that from 2.5 V to 5.5 V, although at lower supply voltages, it may cut signals with a larger amplitude.
The documentation also shows that the power supply must be blocked also capacitor with a larger capacity, it is nowhere to be seen on these boards, so you probably need to solder it personally.
The power supply of such an amplifier should be connected with as short as possible cables with a sufficiently large cross-section , this spider of thin wires can act quite unpredictably.
The problem may be the BT module, if it has a USB socket, it can be provided with a voltage of 5 V, the power supply from the cell (maximum 4.2 V) may be too low.
What's that little rectangle in the schematic?

Łukasz7929 wrote:

Should I walk on my back with the battery?

18650 batteries are not as capacious as some people think (I am writing about it not for the first time because people want to build a 2x30W bluetooth speaker).
As a colleague mentioned 5V and it must be a stable voltage, so some cheap impulse converter is not a good solution.

Łukasz7929 wrote:

When I connected the akku in series, BT is supposed to be powered, because the diode is flashing, but the speakers are not playing.

Or too high voltage, approx. 7-8V (you can damage something with serial connection).

Which exactly rectangle? the one at the bottom (red and black)? this is a switch

Maybe first check that the BT module works properly with the supply voltage from cells connected in parallel. Connect headphones instead of an amplifier.

krzysiek_krm wrote:

Maybe first check that the BT module works properly with the supply voltage from cells connected in parallel. Connect headphones instead of an amplifier.

I do not know if I understood correctly, I should connect the akku in parallel -> disconnect Jack from the amplifier -> connect the headphones with the jack?

Added after 10 [minutes]:

By the way, I would like to cordially greet one person who commented on this topic and at the same time deleted the post in which she wrote to connect akku in series. Fortunately, I have a second amplifier.

Łukasz7929 wrote:

I do not know if I understood correctly, I should connect the akku in parallel -> disconnect Jack from the amplifier -> connect the headphones with the jack?

Originally you have two cells connected in parallel, they cannot be connected in series because the voltage will be too high for the amplifier.
To determine if the problem is an amplifier or a BT module, eliminate the amplifier for a while and connect headphones to the BT module output. Maybe it needs a 5V power supply, you can get from 2.8V to 4.2V from the cells currently connected in parallel, depending on the charge level.
If the headphones sound bad, just in case power the BT module from 5V via the USB connector. If it is still bad - the module is probably damaged. If it is fine with 5V and 2.8V - 4.2V it will be bad, it means that the BT module requires 5V power supply.

I connected the headphones connected to BT to the charger from the phone and I will say that the sound is ok. There is no noise. On the first volume level you can hear a slight murmur, almost inaudible, and this is ok.

Łukasz7929 wrote:

I connected the headphones connected to BT to the charger from the phone and I will say that the sound is ok. There is no noise. On the first volume level you can hear a slight murmur, almost inaudible, and this is ok.

This shows that the BT module is generally functional and undamaged.
Now try to power the BT module with a single cell (or as in your original system with two cells connected in parallel, it does not matter, with a parallel connection it is still the voltage of a single cell). It would be best if you would charge this cell "fully" and test the power supply of the BT module while checking the voltage of the discharging cell, I hope you have a voltmeter. At a certain voltage of this cell, the BT module may stop working properly (or not), you will have another test performed - the range of permissible supply voltage of the BT module. When this is known, we will consider further.

krzysiek_krm wrote:

Łukasz7929 wrote:

I connected the headphones connected to BT to the charger from the phone and I will say that the sound is ok. There is no noise. On the first volume level you can hear a slight murmur, almost inaudible, and this is ok.

This shows that the BT module is generally functional and undamaged.
Now try to power the BT module with a single cell (or as in your original system with two cells connected in parallel, it does not matter, with a parallel connection it is still the voltage of a single cell). It would be best if you would charge this cell "fully" and test the power supply of the BT module while checking the voltage of the discharging cell, I hope you have a voltmeter. At a certain voltage of this cell, the BT module may stop working properly (or not), you will have another test performed - the range of permissible supply voltage of the BT module. When this is known, we will consider further.

Thanks for the new info. Tomorrow I will modify my loudspeaker layout, improving, among others February + I have to replace the amplifier for this, which burned down due to a hopeless hint from one of the users.
I also asked one person who knows electronics and helps me build this speaker and suggested that I try with a converter (0.9-5V to 5V 600mA USB FVAT).
Maybe the admin won't kill me if I add a link here:
http://allegro.pl/przetwornica-0-9-5v-na-5v-600ma-usb-fvat-i6746174974.html

I think that with a meter for PLN 10 I will do something, and if not I will buy a better one.
If I manage to define something, I will let you know!

Łukasz7929 wrote:

0.9-5V on 5V 600mA USB FVAT

If the new amplifier is of the same power, i.e. 6W in total, the current needed for proper operation will be approx. 1.5A (higher than the inverter is able to obtain). This is a remark about the meter, if you can use it, the one for PLN 10 is enough.
Analyze Ohm's law because it is the basis of electronics, so it will be useful in the future when you play DIY projects.
I will not mention the issue of a cheap converter, because I advised against it earlier, for obvious reasons, it is the main source of interference in audio systems.

Correct the link because the moderator will certainly ask for it. As you have to, you provide the auction number allegro or a pictorial photo because it will not disappear on the electrode server and will be useful to other readers.
Such attention to the future.

Yes, but the amplifier will be powered from the akku, and the converter will be BT
Added after 19 [hours] 48 [minutes]:
Added after 3 [minutes]:
I will say this:
- I connected the baskets from the akku to the entrance to PAM,
- I connected the jack cable to the phone

I tested the sound and this is what I wanted to achieve, 0 hum.
However, I would prefer it to be a BT speaker: / In about two days a converter from Allegro should come and I will test it.
If anyone has any comments, please write! :)

I have connected the converters to the system and the problem is that when I turn on the loudspeaker, the current flows first through one element, and then through the other. In my opinion, there is no full current flow, only a break.

I desoldered the plug from bt and soldered the cables connecting the bt to the inverter, because the bt plug was burned out.

[movie: ccc3193b45] https://filmy.elektroda.pl/61_1502390664.mp4 [/ movie: ccc3193b45]

Added after 16 [hours] 17 [minutes]:

I even charged the cells (to 4.2V max) and then the same.

Added after 10 [hours] 44 [minutes]:

I have already answered the question myself. My charger was probably blown :P

I replaced it and it works fine on BT and on the JACK CABLE itself.

Greetings,
Subject to be closed.