B-52 effects loops

[DropKick74]

I play with a B-52 at100 212 combo amp using a squier strat with some awesome pickups (blackouts) and my other strat has two SD ssl1's and an ssl5
my problem is this. My effects loop takes away all my treble sound when i switch it on even when my pedals are off. this leaves me with nothing but mud. the only way i have found to cure this is to turn my channel volumes way down and raise up my master volume. this is hard because it then gets very tricky to balance out my clean and gain channels since my clean is a very loud channel as it is.

My board looks something like this

Return----->Line 6 dl4<--->Digitech cf-7<----> amp Send
Output<>Boss NS-2<>Seymour duncan Pickup booster<>TS-7<>Wah<>Input

Could the problem be in my pedals cuz if i just patch my loop with a cable it doesn't do this.

any help would be greatly apprecieated .

Also i heard this may be something with my amp being a serial amp vs a parrallel amp. what is the difference and does any one know i this is true on an AT-100. also, what would go into modding my amp to become a parrallel effects loops.

[Don Moose]

if i just patch my loop with a cable it doesn't do this.

This is the key statement - you may have a bad pedal, but more likely a/some bad patch cable(s) - you were lucky enough that the one you picked to try a straight patch was a good one.

Try them all, one at a time.

Then try the FX one at a time with 2 cables you've just proven good. Use the same pair of cables for all of these pedal tests. If one of the pedals is bad, make sure the battery is fresh or the wall wart is a) secure and b) the right one.

Hope this helps!