briank1179
Posts: 36
Joined: Wed Jun 29, 2016 4:40 pm

Speaker Static and Popping

Mon Aug 02, 2021 5:43 pm

I'm working on a project that uses a Raspberry Pi 3 with a LCD screen and a salvaged "Bluetooth" speaker. The speaker is connected to the audio jack on the Pi through a PAM8302 amplifier. On the initial configuration both the LCD and Amp were powered from the Pi. Playing WAV files worked great. However, running a script that displayed various images on the LCD resulted in the speaker popping every time the image changed. Changed the configuration by supplying power to the amp using a separate power source. This resulted in a lot of static coming through the speaker.

I'm seeking recommendations on what to do to eliminate both the popping phenomenon and the static.

Your help is greatly appreciate.
Brian

pidd
Posts: 2527
Joined: Fri May 29, 2020 8:29 pm
Location: Wirral, UK
Contact: Website

Re: Speaker Static and Popping

Mon Aug 02, 2021 6:04 pm

Are you sure are using pin 2 of the jack for audio earth and not the sleeve (which is the composite video signal).

briank1179
Posts: 36
Joined: Wed Jun 29, 2016 4:40 pm

Re: Speaker Static and Popping

Mon Aug 02, 2021 6:39 pm

I will check that.

Thank you for the information!

LTolledo
Posts: 5852
Joined: Sat Mar 17, 2018 7:29 am
Location: Anime Heartland

Re: Speaker Static and Popping

Mon Aug 02, 2021 9:44 pm

use I2S Audio DAC...even the DIY ones.....
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

briank1179
Posts: 36
Joined: Wed Jun 29, 2016 4:40 pm

Re: Speaker Static and Popping

Tue Aug 03, 2021 1:08 pm

Taking the advice from pidd, I ohm'd out my connection from the audio jack to the amp board. I'm going through a modified audio cable, using the 1/8(3mm) plug in the jack and the opposite end wired to the board. Referencing at the bottom of the Pi board, the 5-pins on the jack, this is what I recorded;

From A+ on the amp board the ohmic values on the Pi pin-1=1.8K pin-2=1.8k pin-3 = 1.8k pins 4 & 5 = 0
From A- on the amp board the ohmic values on the Pi pin-1= open pin-2 = open pin-3 = 0 pins 4 & 5 = 1.8k

Does this sound "within" the ballpark?

LTolledo are you referencing something like this board = Adafruit I2S Stereo Decoder - UDA1334A?

Again, I appreciate all your help on this!!
Brian

LTolledo
Posts: 5852
Joined: Sat Mar 17, 2018 7:29 am
Location: Anime Heartland

Re: Speaker Static and Popping

Tue Aug 03, 2021 2:28 pm

I'd usually recommend the pimoroni pHAT DAC if its available, then solder headers with long pins:
pHAT DAC long headers view1.jpg
pHAT DAC long headers view1.jpg (171.44 KiB) Viewed 389 times
note: this is just a mock-up, so the pins weren't soldered.. but you'll need to solder those...if you need to get it working

if the pimoroni pHAT DAC is no longer available... you can make a similar one using the I2S DAC pictured below:
I2S DAC Module.jpg
I2S DAC Module.jpg (67.6 KiB) Viewed 389 times

you'll still need:
20x2 headers with long pins
a perfboard to mount the module pictured above
some wires
and some good old soldering technique...
it is installed by simply adding this to the /boot/config.txt file

Code: Select all

dtoverlay=hifiberry-dac
one may also forgo of the perfboard, and just do direct wire connection relevant pins on the underside of the RPi headers


pictured below this is one of my uses for that I2S DAC:
audio DAC module on RPi universal proto board.jpg
audio DAC module on RPi universal proto board.jpg (72.6 KiB) Viewed 389 times
but this one is on the top layer of 3 layers....(first layer is RPiZW, 2nd layer is buck converter board with connector for I2C signals)

the audio quality, even with that cheap I2S audio DAC, is way better (clearer, crisper, more volume) than the one coming from RPi's audio jack..

there are I2S DAC that has extended header pins installed, or gives the user the option to install one...

looking at the item referenced from Adafruit... it seems OK...
however... the setup is quite "cumbersome"

also do stay away from I2S DACs that use MAX98357A as it still pops and crackles....
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

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