Forum - Recent Threads

The PAM8403 amplifier is very noisy

me_Cris — Sat, 25 Apr 2026 15:37:31 GMT

Hi!

I was thinking of participating in a challenge but I ran into another challenge. [emoticon:98f842990f454422aa6a04953955f9d9]
I'm using a small circuit with PAM8403 as a replacement for some speakers with dead audio circuit. In addition, I also have addressable LEDs in the case (this how they came) and I was thinking of using an MCU to control them. But I just noticed a very sharp and annoying noise produced when I power the LEDs, and it doesn't go away even when playing music.
I made a msall PCB, the schematic is below. The power supply is at 5V [USB]. I placed some capacitors in the idea to support the supply voltage.
What ideas do you have? What could I improve?

Thanks!

The schematic:

The layout:

PAM8403 module:

The initial amplifier + controller board:

The speakers:

My assembly:

RE: The PAM8403 amplifier is very noisy

me_Cris — Tue, 05 May 2026 15:01:05 GMT

Of course, you can see in the post.

RE: The PAM8403 amplifier is very noisy

geralds — Mon, 04 May 2026 16:31:29 GMT

Can you make photos of your assembled amp., that show us details about your built?

RE: The PAM8403 amplifier is very noisy

me_Cris — Mon, 04 May 2026 14:35:23 GMT

I did a test, I used the 5V power supply from the board to power another circuit also with addressable LEDs, and the noise is reduced (not by much) than when using LEDs that are already on the speaker. The noise source (addressable LEDs) being further away has some positive effect.

RE: The PAM8403 amplifier is very noisy

me_Cris — Mon, 04 May 2026 14:29:39 GMT

I'm waiting for the PAM8406 version which should not be so noisy.
I didn't achieve much using the ferrite bead + capacitors filter.

RE: The PAM8403 amplifier is very noisy

me_Cris — Mon, 04 May 2026 14:27:23 GMT

I experimented a little by inserting a filter, I didn't use the same speakers (it's more difficult than it seems) but I noticed some reduction in "noise".
Waiting for my PAM8406 version to arrive which should be improved on this side.

RE: The PAM8403 amplifier is very noisy

me_Cris — Tue, 28 Apr 2026 15:29:10 GMT

Not really, but maybe I don't need to go that far. I can also try other 5V powered circuits.

RE: The PAM8403 amplifier is very noisy

me_Cris — Tue, 28 Apr 2026 15:26:49 GMT

Thank you, I will check that filter circuit.
The PCB version is a bit homemade, so I can't make any claims.

RE: The PAM8403 amplifier is very noisy

me_Cris — Tue, 28 Apr 2026 15:22:50 GMT

The PAM8403 module of this type is a little noisy (it's not for nothing that it costs very little), but it's clear to me that the LEDs produce a very sharp sound (I would describe it as a very annoying mosquito sound, I know it sounds strange what I'm saying 😵).

RE: The PAM8403 amplifier is very noisy

me_Cris — Tue, 28 Apr 2026 15:17:28 GMT

Hi, I'm a little late with the reply, I don't have much time during the week. 😅
I added pictures to the post.
I'll experiment with the USB power supply part.
I think LEDs (there are 7 per speaker) of this type consume enough mA (tens), and since I want to create some visual effects, I'm basically witnessing a "symphony" of noise.

RE: The PAM8403 amplifier is very noisy

geralds — Mon, 27 Apr 2026 15:03:42 GMT

You're welcome.

Oh, yes me too - I also have toys I can't remember why I have it. :)

You mentioned the Vref _pin and -capacitor:

It is important to know that this pin is a bi-directional pin.

In the datasheet is descripted you need a X7R cer. cap. between 470n to 1u.

>>> Analog Reference Bypass Capacitor (CBYP)
The Analog Reference Bypass Capacitor (CBYP) is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, CBYP determines the rate at which the amplifier starts up. The second function is to reduce noise caused by the power supply coupling into the output drive signal. This noise is from the internal analog reference to the amplifier, which appears as degraded PSRR and THD+N.
A ceramic bypass capacitor (CBYP) with values of 0.47μF to 1.0μF is recommended for the best THD and noise performance. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown.

>>>

But on the EMB is mounted a 100n X7R cap. This value is too small.

This pin, Vref can modulate the signal through the signal path if that Vref value is not stabile.
Noise and popping noise signals are going to the amplifier.
This cap. must be mounted very close to the pin and the GND must be a polygon field. - The polygon should be around the IC as well.

RE: The PAM8403 amplifier is very noisy

shabaz — Mon, 27 Apr 2026 14:20:19 GMT

Hi Gerald,

Thanks for the info, that part looks much better than the 8403. No reason to use that old part anymore. I can't recall the reason I had the 8403 board, I think I got it several years ago.

RE: The PAM8403 amplifier is very noisy

geralds — Mon, 27 Apr 2026 13:17:19 GMT

Hi shabaz

Here are the datasheet and an app-note. The PAM8403 is obsolete, the PAM8406 is recommended.

community.element14.com/.../PAM8403-_2800_1_2900_.pdf

community.element14.com/.../PAM8403_2D00_User_2D00_Guide.pdf

community.element14.com/.../PAM8406_2D00_User_2D00_Guide.pdf

community.element14.com/.../PAM8406.pdf

As I mentioned you will need filtering on the output to the speakers. Also, the PCB needs improved routing.

In the PAM8406 schematics BOM list you have the values of the components.

A huge problem is a GND loop, -ringing and -bouncing.

-> Poweranalog is now part of Diodes:

https://www.diodes.com/search?q=pam&action_results=Go&start=20

Regards Gerald

RE: The PAM8403 amplifier is very noisy

shabaz — Mon, 27 Apr 2026 11:34:05 GMT

Decided to quickly try that amp board, my results won't necessarily help at all since my setup is completely different and I don't have LEDs/microcontroller attached. I'm not near 'scope so I couldn't grab any traces.

I'm using a very high quality audio cable (double shield), but there is about 3 cm bare at the board end. Speaker is 8 ohm (I only wired to the right channel).

For the power supply, I plugged into an Anker mains-to-USB adapter.

It's quite a noisy amp, there's reasonably noticeable hiss. With the 3.5 mm plug unplugged, I hear mains buzz; it needs to be shorted for that to go away, leaving just the hiss.

Then I plugged the audio cable into a battery-powered MP3 player. It sounded fine.

However, then I attached the audio cable to my laptop instead, which was powered from another port on the same Anker adapter. It was intolerable, lots of electronic noise sounds. If I unplugged the laptop and let it run on batteries, then the sound became acceptable again.

I tried a few things; additional decoupling (220uF electrolytic cap on the power rails, no difference. Then added a choke preceding that (a 1 mH common-mode choke with the windings wired together to be a normal single choke), still no difference. Then removed the electrolytic and re-soldered the choke as common-mode, then tried two of them : ) and also tried adding it to the audio connections too. Still no difference.

Then I remembered I was not using the official laptop charger - I attached the laptop to the correct charger, and the amplifier remained on the Anker one. Noises gone. The official laptop one has 1k resistance from the USB shield to the earth pin. The Anker one doesn't have an earth connection (i.e. SELV).

I'm guessing perhaps the laptop puts enough noise into the charger, that it egresses on all the other ports (common-mode or differential or both - don't know, guessing both!), and the filtering I was doing wasn't sufficient - I should have tried both differential and common-mode simultaneously but I didn't get a chance.

RE: The PAM8403 amplifier is very noisy

michaelkellett — Mon, 27 Apr 2026 09:11:57 GMT

Do you have an oscilloscope.

It will be much easier to fix the problem if you know what it is causing it.

Since the noise happens when the LED is on it should be easy to see what is changing on the amplifier when that happens.

RE: The PAM8403 amplifier is very noisy

geralds — Mon, 27 Apr 2026 08:48:42 GMT

Hi,

please take a look in this datasheet.

https://www.alldatasheet.com/datasheet-pdf/view/246505/PAM/PAM8403.html

-> page 10, figure 2: here is a description about an EMI filter, which helps to reduce EMI.

It seems your amp_PCB is not RF stabile; its layout is not optimized as well. Its GND trace is very small.

As well your PS_PCB please reroute for low noise and low impedance.
-> short traces as you can do, separate in-going from out-going, signal traces need pairing (parallel going) with GND not with V+.

3W output at 5V supply produce a relatively high and fast impulse current into the speakers, separate is it from input traces.

RE: The PAM8403 amplifier is very noisy

shabaz — Mon, 27 Apr 2026 07:04:05 GMT

It's difficult to completely remove noise when a lot is outside of your control; even some so-called hi-fi products get noise artifacts when things are interchanged in setups the manufacturer didn't expect.

Are you sure you're not expecting too much; what is the noise level in comparison to the audio level, and what does the noise sound like? Could you record it?

I happen to have one of those PAM8403 boards here, but I've never used it. I've buzzed out pin 8 which needs to be connected to a bypass capacitor according to the IC datasheet, and confirmed it's present, so the basic minimal circuit is at least implemented on that module.

I will try to power it up sometime, but no guarantee I can do that this week. Not sure it would be all that useful to you anyway, since I don't have the same setup as you.

If you can power-down everything else (LEDs/microcontroller), and remove the input (and maybe even short the inputs) then check to see if the noise is reduced a lot. Then try to add in the audio cables, and feed in audio from something completely separate and battery-powered to begin with, such as a portable MP3 player. Just take baby steps, and see what affects the noise.

I suspect that you may eventually reach a point where the noise is low, but still noticeably there, unless you're prepared to change things a lot, e.g. say switch from USB power to battery, or not use the LEDs/microcontroller if not required, and so on.

RE: The PAM8403 amplifier is very noisy

acdc90 — Sun, 26 Apr 2026 19:21:36 GMT

can you measure the current the complete led circuitry is drawing?

and try an inline choke to power the leds

maybe a photo of the old board and complete unit ?

RE: The PAM8403 amplifier is very noisy

me_Cris — Sun, 26 Apr 2026 10:01:07 GMT

I have some PC speakers powered by 5V [USB], the original board had a digitally controlled amplifier [via push buttons] and an unlabeled IC [for LEDs], all on the same board. The PAM8403 is a module soldered onto a PCB, and for the connections I had to use JST connectors.
I don't know much, but I'm still experimenting.

RE: The PAM8403 amplifier is very noisy

Gough Lui — Sat, 25 Apr 2026 22:57:10 GMT

Most likely this is just digital noise coming through - you need to make sure you've got good routing to avoid it being picked up, good ceramic bypass capacitors nearby, ideally a separate analog ground plane that joins the main ground away from the digital and perhaps even consider some kind of filtering on the power (e.g. inductor choke) if it's really bad.

Ensuring the bypass on the LEDs is good is also important, especially if you have a bad ground, the noise could come around due to ground bounce. The addressable LEDs are PWM so they switch on and off "hard" and that modulates your supply and power distribution network.

Personally, I'd say using a differential input audio amplifier, rather than a single-ended type like you have, would be a better choice and routing pairs of audio lines to that amp, that way if the noise is induced, it is induced into both legs of the audio signal and thus cancels out.

RE: The PAM8403 amplifier is very noisy

me_Cris — Sat, 25 Apr 2026 20:21:47 GMT

It's a single PAM8403 (the little circuit you can buy anywhere).

It's a single power line, 5V via USB (so lots of options). I put in several capacitors to support the power.

The old board contained the amplifier and a controller for the LEDs, but it is damaged.

RE: The PAM8403 amplifier is very noisy

acdc90 — Sat, 25 Apr 2026 20:00:04 GMT

i can see you have 3 seperate capacitor groups, Are you going to have 3 seperate amp boards,?

where is the 5v coming from is it from a switch mode regulator or battery controller,?

does this regulator have a biger size cap like 220uf where you are getting your feed from?

can you make a second regulator to supply the leds seperatly ?

RE: KiCad 10 is almost here

geralds — Mon, 20 Apr 2026 08:14:02 GMT

It's a coffee landing area! 😂

KiCad 10 is almost here

shabaz — Wed, 11 Mar 2026 15:53:15 GMT

KiCad 10 is about to be released soon (release candidate 2 is available), and I just recently checked out the new features list.. I'm surprised, that's a massive amount of features, and many of them look interesting.

Some of the features I can see myself using:

* Ability to implement jumpers properly

* Hatched fill - very useful for marking off areas of PCB on a silkscreen

* Something they call auto-route preview, which I believe just shows a possible routing completion for a single trace

* Dark mode for the application

* More graphical capabilities, such as scaling, and ability to precisely enter co-ordinate values for shapes

* PCB sub-circuits (I think)

For anyone not familiar with KiCad, but wishes to try it, I'm biased but still think one could do worse than viewing the 50-minute video I created a while back (ad-free, it's not monetised). The KiCad user interface has not significantly changed since the video was created.

A lot of beginner video tutorials initially avoid how to create custom symbols and custom footprints, but I included that in the 50 minutes, since it is key information needed for almost any project.

Creating Circuit Boards with KiCad

For other CAD software users, anyone tempted to give KiCad a tryout this year?

Also, there are other CAD version import capabilities, but personally I reckon that's not the best way to transition across, and is possibly more useful to users who are slightly familiar with KiCad, and then need to port across a few of their projects. Reason is, all PCB CAD systems implement some things differently, and you may want to tweak things after import, which is easier when you're at least slightly familiar with the new CAD package, by trying a few projects from scratch.

RE: KiCad 10 is almost here

shabaz — Sun, 19 Apr 2026 17:54:20 GMT

The first dot-release (10.0.1) is available, it fixes a lot of issues (issues list). I raised one bug on 10.0.0 and that was fixed within days.

In general I found the original 10.0.0 was usable, but I had to save files frequently, just in case it crashed (it didn't corrupt anything) and worst-case I'd lose a few minutes of work. Hopefully 10.0.1 is more stable, since 32 crash reasons are apparently fixed in that!