This bug has been copied from bug #678074 and has been proposed to be backported to 5.6 z-stream (EUS).
in kernel-2.6.18-238.7.1.el5 linux-2.6-sound-alsa-cache-mixer-values-on-usb-audio-devices.patch
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0429.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Setting the capture levels on the Line-In capture channel when using an ARX USB I/O sound card for recording and playback did not work properly. The set values were not persistent. With this update, the capture values are now cached in the usb-audio driver leaving the set capture levels unchanged.