If you really wanted to keep the pedal for its sounds then you can get the keeley mod to fix the volume drop... but it does alter the tone significantly still... I used to try to match the loop-switched-out tone with a EQ-7 or similar pedal in the loop with DL-4 to get the hi-end loss back, but thats only with switchable loops like road king/roadster etc...
if its a permanent loop (like stiletto etc.), make sure you are in active bypass mode and not true bypass (hold buttons 1 + 3 while off and then plug the input jack in to swap modes)...
this way the affected sound is always the same when delays switched on and off and should not pop...
If you have permanent loop and need a way to switch delay out but keep the unit active and eliminate trail-off, do the same thing with the DL-4 and EQ-7 but through a LS-2 line changer or similar so you are switching the delay in and out of a loop with its own freq compensator... And, since eq units and the line selectors usually have master levels, you can get your volume drop back and thus saving on having to buy all that crap and an expensive mod.
hope I said all that ok, thats a lot of blurb... hope its helps any too.
