So i picked up josh's DL4 to play with, and now i'm noticing some poor gating in my tone when playing quietly.
I don't know how much of this came through the cam accurately, but here's a vid explaining it as best i could.
[VIDEO]http://www.youtube.com/watch?v=3wgky7bZMgY]6505+ noise gate issues with delay in loop - YouTube[/VIDEO]
First of all I wouldn't run the delay pedal through a gate as the gate will cut off the echoes. Even with the g-string, which is supposed to 'intelligently' cut noise by telling if you're playing at the time to kill pedal noise, you may not be playing while the repeats sound.
That all said, the things I'd look at are:
i) Does it do it if you just run it straight into the front of the amp?
ii) Are you using the loop on the amp? Not sure.
iii) What are your pickups?
iv) How old are the tubes in the 6505+? It is a very, very noisy amp all on it's own, anyway...
v) Are you using the Line 6 PSU? The DL4 takes 12V AC IIRC, and running at a lower voltage will reduce headroom.