Since you're recording sound OK - my guess is either the sound level is
set too low and so you hear hum when you put SB volume up.  Another
possibility is that hum is coming from another source (i.e. mic socket
with no mic attached) being mixed into capture sounds.

Whatever the reason you have to experiment to determine the cause but
first understand what affects the desktop sound volume being captured
and record by "arecord". Using amixer or alsamixer set the Capture gain
level at 100%.   The desktop volume control should be at 100% - if you
have a laptop or a PC whose speakers do not have their own analog
speaker volume control and you are relying on the PC's digital volume
control this will be loud for a user but it is probably what is making
the low signal level for WaveInput. 

You can experiment by having a shell window open with arecord with the
following command.  You may nbeed to replace the Alsa device default
with the device which you have found works from you test with krecord.

arecord -D default -V stereo -f cd -t wav record.wav

This will show signal levels of the signal being recorded into
record.wav.  The levels should be around 90%.

With a audio source playing - check the arecord levels move. Then
adjust the desktop volume using kmixer to see the effect and try to get
either level to peak at about 90%.

Stop arecord and play back the recording to see if the hum goes away. 
If there is still a hum you can repeat and set the gain levels of the
other input sources such as microphone and line-in to 0% and capture
gain to 100% to ensure you have no stray sources.

After each set of tests - you should listen to record.wav to find out
what level gets rid of the hum.


-- 
bpa
------------------------------------------------------------------------
bpa's Profile: http://forums.slimdevices.com/member.php?userid=1806
View this thread: http://forums.slimdevices.com/showthread.php?t=49584

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