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motorcycle noise when playing most video

Posted: Fri Sep 27, 2013 11:28 am
by ViolentMonk
Right now I'm using Raspbmc on a model B. I have been putting this down to the bad analog sound but I'm not sure. I get this weird low pitch rumble noise (loud enough to give you a headache over time) in the background while playing back some videos also the noise stops after stopping the video but when I move around in the menu with my IR remote it makes the noise again but only after every push until I reboot. I cut the power wire in the powered usb hub I'm using so its not back feeding power.

Re: motorcycle noise when playing most video

Posted: Fri Sep 27, 2013 12:47 pm
by redhawk
If you touch any metal part of the Pi (i.e. LAN / USB holder) does the noise go away or get reduced in intensity??

Richard S.

Re: motorcycle noise when playing most video

Posted: Fri Sep 27, 2013 3:41 pm
by dom
It's coming from either the power or ground signal. Can you disconnect anything plugged in that is not essential.
Can you power it with a different supply as a test (e.g. try a PC/laptop USB port).

Re: motorcycle noise when playing most video

Posted: Sat Sep 28, 2013 4:58 am
by ViolentMonk
all I have plugged in is the powered usb hub with the power wire cut in the usb cable end, the usb thumbdrive plugged into that and the sd card needed to boot. the noise doesn't subside by touching anything and nothing is loosely connected or dusty also I changed the power supply to a different one and it still does the same thing so I dont think its the psu. going to see if I can bring it over to a friends house and see if it makes the noise through hdmi.

Re: motorcycle noise when playing most video

Posted: Sun Sep 29, 2013 11:23 am
by dom
Can you try with USB hub disconnected and (I assume you are using composite?) try disconnecting the TV when audio is playing.
Is the mains power coming through anything (e.g. a 4 way adaptor with other things plugged in)? Does plugging it in elsewhere help?

Re: motorcycle noise when playing most video

Posted: Mon Sep 30, 2013 4:06 am
by ViolentMonk
I am using an hdmi to dvi adapter with the analog sound cable 3.5mm to red and white rca. when I started the pi up without the hub it seemed to work normally for a little then it restarted on its own (only once so far though) also it still has the noise. is there a way to fix it? its not the 3.5mm to rca cable because I used it with my computer and it has perfect sound.

eh well I connected my pi to a hdmi tv to see if it was the same as analog audio and it seems like the annoying sound is gone.. think an audio extractor would work? the tv im using has red an white analog sound or optical. also it isnt the TV or the hdmi adapter because my 360 works fine using the same setup.

Re: motorcycle noise when playing most video

Posted: Mon Sep 30, 2013 6:14 pm
by dom
As I keep saying, get it in the state where it is making the noise. Then unplug *everything* not essential. You shoud be left with just the audio connection and the power supply.
The HDMI->DVI adapter should be unplugged. The hub and any USB devices should be unplugged.

Does it affect the noise?

Re: motorcycle noise when playing most video

Posted: Tue Oct 01, 2013 11:23 am
by ViolentMonk
um so its okay if I unplug the hdmi cable while the pi is running?

Re: motorcycle noise when playing most video

Posted: Tue Oct 01, 2013 11:27 am
by dom
ViolentMonk wrote:um so its okay if I unplug the hdmi cable while the pi is running?
Yes.

Re: motorcycle noise when playing most video

Posted: Wed Oct 02, 2013 7:41 pm
by chilinski
When dealing with audio "noise," it is always a good idea to first check your grounds.

Much like when you have problems with your Pi you check power first.

Re: motorcycle noise when playing most video

Posted: Fri Oct 04, 2013 12:26 am
by ViolentMonk
chilinski wrote:When dealing with audio "noise," it is always a good idea to first check your grounds.
how do I do that?

Re: motorcycle noise when playing most video

Posted: Fri Oct 04, 2013 5:14 pm
by mcfleeg
Not sure if this is related, but I was getting a bad hum on the analog audio output port. I fixed it by hacking an RCA cable, plugged it into the composite video port, and grounded it to the screw of the AC outlet (US).

Could be bad power, power supply, or something else...like a ground loop of sorts. Rather ugly fix, but it worked for my application.

cheers.
-Lee

Re: motorcycle noise when playing most video

Posted: Mon Oct 07, 2013 10:04 am
by ViolentMonk
welp I haven't figured out what causes this but I switched my pi back to openelec and it seems the sound for some reason works better on it. no weird high pitch electronic explosion sounds when starting a video and the volume level actually goes up when you bring the dba up in the audio settings so I can leave the tv volume low without having to listen to a biker in the tv. (when I bring the tv volume over "40" it does the bike sound for raspbmc) when the raspberry isn't connected through analog sound it magicly stops(so it isn't the tv) also sound over hdmi works fine off a different tv.

crazy electronic explosion happened on almost every new raspbmc only on the nightly build labeled "speed" worked without the explosions but that build's volume amp was missing or something.