Question on volume control

[fwcrawford]

I was testing some headphones with my Sovereign GT this afternoon and noticed that when I adjust the volume control on the detector to about 3:00 and set the threshold to just audible, if I turn the volume control further to max, the threshold disappears.
This is happening while the detector is stationary and not while detecting.
I then have to adust the threshold control again to get the audible signal... does this sound normal?
I tried several pair of headphones and then tried it with just the external speaker and had the same senerio.
I know the manual states that the recommended setting for the volume is max, but I don't understand why the threshold disappears as I turn the volume control to max.
Can someone test their detector to see if they get the same results as I do?
I appreciate any help on this question.
Thanks,
Felix

 

[JHM]

Mine does the same thing.

 

[fwcrawford]

n/t