Cannot get equal Left and Right input levels

[hp1]

Ok I have a strange problem. My hardware is:

EEEPC 901 Linux
USB Sound Card (Media Asistance with a Kronauer Chipset I think)

I am currently running the 1.3.5 Beta but had the same problem on the stable version

I can get Audacity to recognise the USB card no problem i did this by changing some settings in Control Center as in this post:

http://forum.eeeuser.com/viewtopic.php?id=26456

if you adjust the input levels in ALSAmixer the left and right levels in Audactiy will NEVER match. One is always higher than the other depending on how many steps you nudge the input level bar in alsamixer.

Unfortunately I cannot find any information on whether my soundcard is compatible with audacity (though it recognises and records except with the above problem).

I am a newbie with linux and so I dont know how to diagnose whether this is an ALSA, OSS, driver problem etc. I was hoping somebody could assist.

Sorry for the long post, just wanted try and explain as well as possible.

cheers

[steve]

Tell a bit about what you are recording from - from a CD player? What wires have you got plugged in? Lots of detail is good.

[hp1]

Well my ultimate goal is to record mixes from my decks through my mixer. The output from the mixer is a proper 'Rec' output so the left and right are balanced.

I have also tried recording straight from my MP3 player as well using the headphone socket with the output selected to 'line out', again with L + R likely to be balanced.

Both of the above give the same results as described in my original post.

As a matter of interest the I have used the sound card successfully in XP recording through Nero Wave Editor (yuk) but the laptop is ancient (AMD 550MHz!!) hence why I wanted to be able to use my new Netbook instead.

Not sure what more detail I can give you. I have done a bit of research on the Soundcard (its not a very common one); and it looks as though the chipset is used in quite a different number of other cards that are linux campatible which gives me some small ray of hope that I can solve this!

[steve]

When you say that the left/right levels never match, how far out are they? How close can you get them?
Is it always the same channel that is louder than the other? (which one?)
If you swap the connectors that go to the left / right outputs of the mixer, then what happens?
Are you running AlsaMixer in a terminal window?

[hp1]

1. They are really far out, enough to notice on the output display meter, enough that the waveforms are noticeably lower and you can hear it when you listen to a recording. I can never get them close, trying to adjust the left and right seperately in alsamixer does nothing.
2. Thats the strange thing, I touched on it in my OP, when i nudge the slider in alsamixer (yes the noddy GUI in a terminal window) the lower channel will switch between right or left.
3. I havent tried swapping the outs on the mixer but my MP3 player only has a 3.5mm out with a combined left and right. I'll have a try tonight though just to be sure.

I forgot to mention that I have tried LOADS of different mixers though actually I suspect they are all just front ends for ALSA? Of the ones I managed to insall on the eeepc they all manifested the same problem which makes me think its an alsa problem (or alsa actually just being incompatible with my card?)

[hp1]

Been playing again today.

If I start Audacity and select OSS:/dev/sound/dsp1 as the record device it will record equally but the levels are incredibly low. Now if I then open alsamixer with $alsamixer -c1 to open the controls for card 1 (the usb one) and adjust the line-in control the levels immediately increase but this is when the problem hits...they're not equal. Not sure if this helps.

EDIT: If i use alsamixergui -c1the line-in sliders dont even move! Maybe the card's line-in levels connot be controlled properly via ALSA hence the uneven levels.

I installed ALSA OSS and tried running audacity with $aoss audacity. It didnt make any difference.

[steve]

If I start Audacity and select OSS:/dev/sound/dsp1 as the record device it will record equally but the levels are incredibly low. Now if I then open alsamixer with $alsamixer -c1 to open the controls for card 1 (the usb one) and adjust the line-in control the levels immediately increase but this is when the problem hits...

So when you open AlsaMixer, but before you adjust anything, what recording level does AlsaMixer show? (perhaps a screenshot?)

Are you aware that for most USB devices it is not possible to adjust the recording level through the operating system? The recording level is usually adjusted by either changing the level of the signal that is being sent to the device, or some USB devices have a physical input level control on them. I have never seen a USB device where it is possible to adjust the recording level from the operating system mixer (on Linux or Windows XP).

[hp1]

Hey, I cant post a screenshot for a while because I'm on holiday now for a couple of weeks. When I first open alsamixer using the -c1 parameter the input mixer is at 0 (zero).

I understand what you are saying regarding adjusting leves with the OS but I have definitley adjusted the input level in XP using the slider found in the advanced controls of the Audio settings in c0ontrol panel. I understand that the input levels INTO the USB card are adjusted by actual device outputting the source but what then adjust the levels coming out of the device and into the PC/laptop OS? Are you saying that this is generally a 'default' level and cannot be adjusted? If this was the case why does the slider show up in alsamixer? I'm getting a little confused here!

[steve]

If this was the case why does the slider show up in alsamixer?

I've no idea. I use a Behringer UCA 202 USB sound card and there is no recording level slider for it in ALSA mixer. I have also used various USB sound cards in Windows XP and the recording level slider in the control panel has always been greyed out (unless the on-board sound card is selected). All I can assume is that it is some peculiarity with the Kronauer driver.

[hp1]

Its funny you should mention the Behringer because that is the exact one I was looking at to replace this one. The 202 is very cheap compared to the one we have been discussing but I have heard it sounds ok. As you use it already i assume that it works fine with audacity?

Maybe its time to stick the old one on ebay and try the Behringer, thanks for all the help and assistance.