troubleshooting a new usb audio adapter

[lokeyb]

I just bought a cheap usb "sound card" because my netbook is so noisy when recording directly through the internal soundcard that you can hear lots of noise with the microphone turned off and even unplugged.

it only cost 5€ but it has to be better than the integrated sound. It supposedly has a c-media cm108 audio chip which according to the specs should support 16bit at 44.1 or 48khz. It should aso be usb 1.* and 2.0 class compliant.

I thought that it would just work but beyond jack setup recognizing a usb audio device nothing is really happening apart from nasty loud feed back.

when i select the device in jack, the input meter shows the left input channel constantly peaking (with or without a mic plugged in). When playing back sound all i hear is extremely loud popping sounds.



where can I start for troubleshooting?.. I know it's cheap and rubbish but it's all I've got and my quite extensive research suggested that it should work ootb.

thanks for any advice!

[varpa]

Some standard things to do is to run "aplay -l" to list your sound devices which should show your device.  You can also run alsamixer and adjust the mixer settings and see if that helps.  In all likelihood this is a USB 1.1 audio compliant device and should therefore be fully supported in Linux.  In Jack you can try different settings of Frames/period etc.  I usually safe default is something like 1024 Frames/period, 2 frames/buffer and 44.1 or 48 kHz.   Look at the QJackCtl Messages panel when you run Jack and see if any errors are reported.  Another slight possibility is that the USB connections is sharing an interrupt with another device, so try different USB connectors on your computer if you have more than one.

[lokeyb]

Some standard things to do is to run "aplay -l" to list your sound devices which should show your device.  You can also run alsamixer and adjust the mixer settings and see if that helps.  In all likelihood this is a USB 1.1 audio compliant device and should therefore be fully supported in Linux.  In Jack you can try different settings of Frames/period etc.  I usually safe default is something like 1024 Frames/period, 2 frames/buffer and 44.1 or 48 kHz.   Look at the QJackCtl Messages panel when you run Jack and see if any errors are reported.  Another slight possibility is that the USB connections is sharing an interrupt with another device, so try different USB connectors on your computer if you have more than one.

thanks for taking the time to reply! Your suggestions were very helpful

I had tried all the usb ports and there is unfortunately no difference, I don't know how to check and re-prioritize the interrupts though (or if that's even possible - I'm looking into it now). aplay -l lists the device and it is recognised as "USB AUDIO". Also, other similar commands which I found trawling this forum revealed no clues to me either.

HOWEVER, Looking at the qjackctl error messages showed that there is a stream of x runs when using the adapter and no matter what combination of settings I try in jack I can't escape them.

SO, to make sure it wasn't H/W issue, I quickly tried the device on a 2011 mac which worked fine for output but there was some issue with the input from what i could tell from the visual monitor (it showed a constant 50% sound input level, but speaking into a mic would make it shift slightly). I also tried the device in winxp running in virtualbox with AVLinux as a host. Both inputs and outputs seemed to work fine that way.

The audio chip is supposedly common, usb1.1 compatible and should apparently work ootb in linux so I'm a bit frustrated by this to say the least.

any more ideas?

thanks once again Varpa

[varpa]

I'm a bit stumped on your problem.  I looked on the alsa support page and its not obvious to me how your c-media card relates to the others listed there: http://www.alsa-project.org/main/index.php/Matrix:Vendor-C-Media   You might study the details sections and see if there is anything to try.  Sometimes there are parameters that can be used with the drivers.   You could check what driver you are using with command "lsmod | grep snd" which likely show several sound-related modules.  You can get some information about modules with command: "/sbin/modinfo <module_name>".  There is alsa a command "usb-devices" which gives information about USB devices.  Other general suggestions are to post your problem on linuxmusicians and/or send a query to the Alsa help mailing list (see http://www.alsa-project.org/main/index.php/Mailing-lists)

[pgreenwood]

Did you get this working? I just bought an Alesis iO4 which is a USB audio and MIDI interface. I feared it would not do what I'd hoped it would at first but then found an article about starting jack from the command line, and now it appears everything (audio) about the unit is recognized and jack-connectable.

http://forum.audacityteam.org/viewtopic.php?f=18&t=63419&start=40

In short, it involved making sure that all jack instances were totally dead then restart jack with a special incantation from the command line. My (admittedly naive) sense is that all USB interfaces behave roughly the same way. If the computer recognizes they're there (tail -f /var/log/messages) you're almost home. You just have to start the right software in the right order and make the right software connections.

[linuxdsp]

My (admittedly naive) sense is that all USB interfaces behave roughly the same way

Unfortunately that is very naive - all USB class compliant (mainly USB1) devices will probably work, but anything other than that will require custom drivers.

You just have to start the right software in the right order and make the right software connections.

And there was I thinking that software / driver development was some kind of highly technical skill, I'm obviously doing it all wrong..

[pgreenwood]

I've been using Linux for a long time (starting with Debian Slink on a IIci). I'm no developer. After much due diligence in selecting a desktop replacement, I think I love AVL 5.0.3. I recently did a clean install of it on a Vostro 1320 with the thought that I'd like to experience more of the AV magic that guys like you develop. I had fiddled with some MIDI apps but never connected a mic to this box; let alone a guitar. I've had challenges understanding audio and making AV things work as expected. It seems like others have had similar problems. I thought I'd share my experiences, what clues I found and hopefully help others find a way to make this stuff work. I obviously have a long way to go in communicating with precision, hopefully it'll improve. I hope I haven't set the cause back too far. Thanks for your understanding.

[linuxdsp]

@pgreenwood: Getting audio interfaces to work in linux is sometimes a challenge (especially some of the more esoteric pro-audio devices) - sometimes you can just plug in a USB interface and it all "just works" - especially with an A/V specific distro such as AV linux, but I'd caution against making a general assumption that this will be the case with any USB interface.  It would be a much better situation if interface manufacturers adhered to some agreed standard (and if such standards were properly in place) but sadly, more often than not, some kind of 'persuasion' is required to get the device working.