Noise on analog output
#1
Hey everyone,

I've been searching the forums but didn't find a solution to my problem.

Most of the time, there is noise whenever something on the screen is moving. There are exceptions though, some videos play without this noise, and on certain menu screens, there is noise although nothing is moving.

I run Raspbmc (XBMC 13.2) and the audio is connected to a Stereo amplifier via a jack to RCA cable.

As this is difficult to explain, I shot this short video: http://youtu.be/vFlg9V680EY

Thanks for helping.
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#2
Can you try a different power supply?
Some power supply produce a lot of power/ground noise when consuming higher current (e.g. when GUI is animating) and that gets picked up by the analogue audio.
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#3
Thanks for replying.

I connected the Raspberry Pi to a USB port of another device, do you think this may be the problem? Or do only A/C converters produce noise?
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#4
Was the noise different with another device?
In theory any power supply may or may not be noisy whether A/C or another device's USB port.
Try a few sources and see if the noise improves.

By the way, the B+ has been redesigned to isolate the audio from the power supply, and should perform better with noisy supplies.
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#5
I have no sound problem with any other device, but they are all connected to the A/C.

I'll try and find another power supply, thanks for your help!
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#6
The analogue audio output of the original B (not B+) Pi is quite low in level compared to a typical line level source and also does not filter out power supply noise well as popcornmix says, forcing you to turn up the volume on your amplifier which will also increase background noise.

I do hear a small amount of digital noise on the output of mine as well, as is typical with sources such as laptop headphone jacks. The only thing you can really do is make sure you have a good quality power supply, and make sure you have the audio options set up to optimise the output volume. Eg:

* Don't turn down or adjust the volume in software, use + to turn up XBMC's volume to 100% and leave it there. Use your amplifier/TV volume control only.

* Disable "normalize levels on downmix" in Settings->Audio Output.

* Consider increasing "volume amplification" to about 6 to 9dB. This is done by bringing up the OSD during video playback then going into audio settings. After increasing it, choose the option to save as default for all videos - this will make it the default for all videos played from now on (both those in your library already and those you add later) but you can still manually turn this down for particular videos, for example music videos and the different setting will be remembered for those individual files.

This also adds dynamic range compression which is usually beneficial for movie playback but detrimental for music playback. (Only music within videos is affected, not music only files such as mp3 or aac)

If none of the above is sufficient consider getting the new B+ as the analogue output is supposedly less noisy and also has a higher output level, although I have not tried one myself to confirm it.
Kodi 18.3 - Mid 2007 Mac Mini, 4GB, 2TB HD, Windows 7 SP1
Kodi 18.3 - Vero4k, Raspberry Pi 2. OSMC.
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#7
krapo, i had the same problem as you did. I just needet to change the USB power cable and all that white noise was forewer gone, simple as that Smile
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#8
Changing the power supply doesn't work for me.. still a lot of noise, especially when having a black screen..
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#9
Had this problem, thought it was a problem with my RPi3's analog output, then I found an option called "Send low volume noise" under System/Audio. Switched to off, problem gone. Doh!
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#10
great, thanks for mentioning this option.
When I turned off "Send low volume noise" the background noise went away.
But as soon I start playing a song it returns. Am I missing something? (The noise is definitely not in the audio-track)

Cheers
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#11
(2017-08-01, 18:55)[email protected] Wrote: great, thanks for mentioning this option.
When I turned off "Send low volume noise" the background noise went away.
But as soon I start playing a song it returns. Am I missing something? (The noise is definitely not in the audio-track)

Cheers

How significant is the noise ? The analogue PWM output from the 3.5mm jacks on a Pi is engineered down to a cost level (hence using PWM rather than a DAC) and isn't 'HiFi' quality.
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#12
The noise is quite significant. But I guess this is a matter of opinion.
The noise seems as loud as when I turn on "Send low volume noise".
Is it possible that "Send low volume noise" gets turn on as soon as I play a track? (according to the gui the option is off at all times)
I find it strange that the noise disappears immediatly after stopping a track.

I am thinking of getting this DAC:
http://www.fiio.net/en/products/27
But I don't know if I can make it work.

Thanks
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#13
@krapo

The sample you put on youtube sounds to me like you're not using the new audio mode with your Raspberry Pi. Raspbmc (XBMC 13.2) looks to be pretty old (2014) and I'm not sure if at the time of its release the new audio mode was already implemented (Raspberry Pi firmware). Try to get a newer Raspbmc XBMC version (I'm not using it).
For reference take a look at:
https://www.raspberrypi.org/forums/viewt...9&t=136445

If you're able, try to see if you have audio_pwm_mode=2 in your /boot/config.txt
# New audio mode test
audio_pwm_mode=2
#disable_audio_dither=1

You could also try to check your analog sound output directly with some unpowered headphones and not connected to your amplifier.
Although the noise from ground loops is usually permanent, there are situations in which this noise is very low and it gets amplified only when there is sound coming out. If that's the issue, than look for a 1:1 audio ground-loop filter (it consist of 2 jack adapters and 2 double coils) - it's around 5EUR/USD.

As for other users reporting hearing some noise with "Send low volume noise", I can confirm that and suggest to disable it too, it's also saving some CPU power. Additional "beneficial" Kodi Analog Audio settings:
Keep audio device alive = off
Number of channels = 2
Output configuration = fixed
Maintain original volume on downmix = on
Stereo upmix = off
Sample quality = GPU accelerated
Limit sampling rate (kHz) = 44.1

Also in the Player Setting section:
Movies:
Sync playback to display = off
Music:
Volume Adjustments (ReplayGain)=off

As for the "volume amplification" discussed in a post above, I use 20dB and it works well.

I'm not sure if you really need to invest in a HiFi DAC if you enable audio_pwm_mode=2, as the output with this mode is good quality and crystal clear.
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#14
(2017-08-02, 17:39)acnp77 Wrote: I am thinking of getting this DAC:
http://www.fiio.net/en/products/27
But I don't know if I can make it work.
If your wanting to connect your RPi to your amp via analog RCA, i'd still consider a better quality power supply as has already been mentioned, as well as trying what abga suggestioned in his post.

If you want better quality analog audio, you could consider a Hiberry DAC as some say it's much better than what you get out of the RPi itself. It's cheaper than what you linked to but it's not plug and play. You'd need to do some configurations in software but there are guides around that can help.You can also google for some other RPi audio hat if you want more choice.
I'm a XBMC novice :)
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#15
For less than $40 USD, HiFiBerry DAC+ RCA version (What I use for dedicated music controller) works awesome.

My other Pi's (Raspbian & Kodi) just use HDMI to TV.

Has anyone tried bluetooth speakers?
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