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| USB Audio Adapter to eliminate Ground Loop Interference http://forums.linhes.org/viewtopic.php?f=2&t=18603 |
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| Author: | fitech [ Sun Jul 20, 2008 4:00 pm ] |
| Post subject: | USB Audio Adapter to eliminate Ground Loop Interference |
I had a problem with a lot of loud buzzing coming through my stereo with the audio from my KnoppMyth box connected with a 3.5mm stereo to RCA cable. I tried plugging my stereo and KnoppMyth box into the same power strip, but it stuck around. I determined it was ground loop interference. I just installed a USB Audio Adapter to use instead of the audio jack on the motherboard. Problem solved. StarTech ICUSBAUDIOB USB to Audio Adapter. $19.99 at NewEgg. It was plug and play! Thanks to everyone who has worked on this incredible project. My next dilemma is the Digital TV transition in '09. |
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| Author: | fitech [ Sun Jul 27, 2008 6:35 pm ] |
| Post subject: | Problems Using a Secondary Audio Device |
The USB audio adapter works great for TV shows because you can assign dev\dsp1 to be used for TV show playback in the MythTV general settings. The problem is that most other things seem to use the default, or first audio device available, which is dev/dsp. I have tried to rename or copy the devices so that the USB device becomes the dev/dsp or so that dev/dsp becomes dev/dsp2. I'm not having any luck, probably because I'm really not good with linux. Does anyone have any ideas about how I can configure the flash player, mplayer, and everything else to use my USB audio adapter? Thanks, Dan |
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| Author: | nharris [ Mon Jul 28, 2008 6:20 am ] |
| Post subject: | |
Try disabling the motherboard audio in your BIOS setup. Once your USB audio device is the only audio output, things may just work. |
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| Author: | cliffsjunk [ Mon Jul 28, 2008 9:03 pm ] |
| Post subject: | |
nharris wrote: Try disabling the motherboard audio in your BIOS setup. Once your USB audio device is the only audio output, things may just work.
This trick would probably work without addition for a clean install, but may fail for you due to the fact that it already has an adapter in the "first slot". You may need to do the following in addition to disabling the onboard audio in the BIOS. When I run into this issue I just grep through all of /etc looking for udev rules and etc that may keep your only audio device named as something like /dev/dsp2 instead of /dev/dsp. If you search through /etc (as root) with the following command, you should be able to find the place(s) to change: Code: grep -ir dsp2 /etc/*
If you change all the dsp2's to dsp's and all the dsp's that you find in files that have dsp2's to dsp2's you should effectively swap the order of the two audio devices. It is also easy to put back the way it was. Cliff |
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| Author: | fitech [ Tue Sep 09, 2008 7:43 pm ] |
| Post subject: | Disabling in the BIOS is the way to go |
I should have posted this already. Disabling the onboard sound card in the BIOS makes it all work flawlessly. I love having crisp, clean sound now. The next project is installing a digital tuner card. I'd better get that done soon. |
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| Author: | jayb282 [ Sun Jan 11, 2009 6:18 pm ] |
| Post subject: | |
When getting some other parts i picked up one of these - works a treat. Audio is much cleaner than anything i got off the motherboard. A followup question for those that have used it: Did you need any additional settings changes to get the mixer in MythTV work? I turned off motherboard audio in the BIOS - i have changed no settings in MythTV. I still have the audio device as "/dev/dsp" and the mixer as "/dev/mixer". Audio all works. Problem is, the volume controls in MythTV no longer work. Spent about an hour going thru the settings, but couldn't find anything wrong... cheers -j |
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