alienux

Charlie_Watt, in my case I'm sure it's the adapter, although I've had the problem with several adapters and several different sets of 1/8" headphones. I'm sure the POD is fine because it's the 1/8" end that I have to adjust usually, but once it's set, it's not a problem anymore so I don't worry much about it.

There's a list of dimensions for the various POD models here:
 
http://line6.com/support/page/kb/_/pod/pod-hd/pod-hd-weights-and-dimensions-r206
 
That page has the info for the HD products, and also contains a link to another page with a multi-tabbed spreadsheet with some of the older ones, including the X3 Live. It looks like there is about .29" difference in depth, but not much difference besides that.