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OPI PC plus Analog audio noise crakles


bodtx
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Hi when I use the orangepi PC plus TRRS audio output (analog), I have some glitches which are linked to the video mouvment.
I've tested the connection between ground and video and it seems that on the left ground pin there is a natural link with video output (50 ohms), is this normal?
my cable is a 4 pole TRRS. I even tested audio with cable directly plug on soldering but same result.

How could I get a clean audio output?

note that the hdmi audio output is clean.
and my speaker system is clean if I plug it on a MP3 player with an audio jack.

 

I use retrorangepi 4.2 which is based upon Armbian v5.54 (default legacy kernel)

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i'm not sure if PC plus is different from PC but if i play mp3 audio files directly using mpv on the command line, the sound is pretty clear no glitches

there could be 2 possible related issues, latency due to loads say with video or network latency and possible electrical interference / noise from other sources.

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 OK i've figured out. It was a problem of background loop https://en.m.wikipedia.org/wiki/Ground_l...ectricity)
Amp and opi were on the same power source.
There are many solution but the cheaper and easiest to me was to power the amp (pam8403) with it's own 5v power supply.

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another time when i had the problem is when i connect both my opi pc and a bluetooth speaker (with analog inputs) to the same usb power supply (a multi port usb charger), the 60 hz hum is loud, this i believe is due to currents being overdrawn (i.e. the power supply couldn't cope) and the ripples are amplified by the amplifier

i disconnected the usb charger from the bluetooth speaker and simply run the speakers on its own battery packs, all that noise is gone

so the power supply is an important source of all that interference

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