Comment 4 for bug 970517

I have the same or similar issue:

If I set up to "Do nothing" in Power settings when I close the lid of the laptop it actually locks the screen and then I cannot use the hardware knob of my external USB DAC to increase or decrease the volume.

When I say "do nothing" it ignores the request by locking the screen. The second issue is that there is nothing wrong in using hardware buttons or the knob of external usb dac - if those (hardware) buttons/knobs are not phisically protected then I guess it is normal to be available.