TPA3118 noise and pop sound

[papaarrugada]

Hello all,
I am new in this forum and hope for a short answer.
I have searched in some threads and found some interesting ideas, but want to ask for a suggestion for my constellation:



This are my mono amps:


DC 8-26V PBTL TPA3118 Mono Digital Amplifier Board AMP Module 1*60W for Arduino | eBay



I have on RasPi running a LMS player called piCoreplayer, which can control a mute output. This can be connected over an optocoupler to the mute input of the 3118 board.
Without muting I have a very disturbing noise (with open line inputs too) and a switch on/off pop sound.
And I have two different power supplies for RasPi (5V) and for the mono-amps a 19V DC.


I another thread I found a solution with a protecting board (with delay) in series of the amp outputs to the speakers.


Question:
Makes it sense to generate a delay with the RasPi over GPIO to extend the muting?
Is it always necessary to use the protection boards at the outputs to the speakers?


Many thanks for your answers.

 

[doctormord]

If you have noise on the amps output, your muting isn't working correctly.

 

[papaarrugada]

Thanks for your answer.


When muting is active, I don't have noise.
But the muting is active only 2-3 seconds after starting the RaspI. Then the GPIO outputs are working.


Can I remove the power on/off pop sound only with the muting?
Or is it necessary to use the protection board on the amp output?

 

[doctormord]

Yes you can. Afaik the boards mute input is connected to SDZ, so "low" puts the outputs to High-Z.

To have a power-on mute, put a pulldown-resistor to GND (like 1k) on this pin and pull this pin high with your raspi when playing music.

 

[papaarrugada]

ok, great!


And to reduce the noise during playing or pause I have to change the gain of the amp module?


In another thread I read that resistors are responsible for the max. setting of 32dB. Should I change the values to reduce the noise?

 

[29285]

ok, great!


And to reduce the noise during playing or pause I have to change the gain of the amp module?


In another thread I read that resistors are responsible for the max. setting of 32dB. Should I change the values to reduce the noise?

You may reduce noise by a lower gain setting.
Be aware gain setting is read once on power up, so you cannot change it "on the fly"

 

[papaarrugada]

I understand.

What resistor values should I use?
Is there a "best" setting to avoid the noise?
And which resistor I have to change?

I don't have a schematic diagram from the board.

 

[Khron]

Datasheet: http://www.ti.com/lit/ds/symlink/tpa3116d2-q1.pdf

Page 11, the table at the top, and follow the traces from the relevant chip pins to see what's what.

 

[29285]

The "best" noise performance is achieved at the lowest gain setting, i.e. 20dB voltage gain. The drawback is the inferior sensity of the amp. To yield 10V of output (25W/4Ohm) you need 1V of input voltage.
You will find you have to increase your volume potentiometer to achieve a certain level of output power.
So it depends on the input level that is available to you.
In most cases you will have to find a compromise somewhere in between that suits you.

 

[papaarrugada]

thank you all for your support!

I will report my results.

 

[papaarrugada]

Hi again,
I want to report my results after studiing the data sheet.
I decided realizing a gain of 20dB and changed the resistors.
Noise is very low, but my max. input level was not enough.
Therefore I changed to 26dB, noise is about half in comparison to beginning and my input level was enough.
From both resistors 39k and 100k I left the 100k and placed a further 39k in parallel to the original. This makes 19.5k, best value in data sheet is 20k with 5% tolerance.


I tuned all my 8 amp boards.


Next step is muting from raspberryPi over GPIO pins and a delayed switched relay in the power supply of the amp boards.


Thank you all for the help and informations!

 

[selwe]

Hi again,
I want to report my results after studiing the data sheet.
I decided realizing a gain of 20dB and changed the resistors.
Noise is very low, but my max. input level was not enough.
Therefore I changed to 26dB, noise is about half in comparison to beginning and my input level was enough.
From both resistors 39k and 100k I left the 100k and placed a further 39k in parallel to the original. This makes 19.5k, best value in data sheet is 20k with 5% tolerance.


I tuned all my 8 amp boards.


Next step is muting from raspberryPi over GPIO pins and a delayed switched relay in the power supply of the amp boards.


Thank you all for the help and informations!

@papaarrugada Can you please add some illustrations/pictures/schematics with the mods you made?

 

[papaarrugada]

yes, of course.

gain can be selected with two R's.
The table of datasheet shows following selectable values in master mode:

gain | R1 to GND | R2 to GVDD
--------------------------------------------
20dB | 5,6k | OPEN
26dB | 20k | 100k --> I have selected
32dB | 39k | 100k --> default setting
36dB | 47k | 75k

therefore I had to change R1 from 39k to 20k.
I decided to place a second 39k on the top of the default R 39k.
Two 39k R's results in 19,5k, 20k is the suggested value in the table.
But it's in the 5% tolerance (19k to 21k).

I want to add a picture where you can see the "construction".
But I don't know how I can import a pic.