Okay, i recently bought a Marshall AVT 150H Full Stack;
150 watt valve preamp head with angled and straight 200watt 4x12's,

My problem is about the sound im getting by using my Line 6 Pod XT Live Pedal in the parallel FX Loop.

It seems to create a sound, half made up by the head itself, and half by the Pedal even when the FX Loop Mix knob is in top position for that channel.

There is a small switch on the back of the head between the FX Send and FX Return which changes some amount of input of the pedals effect (it says which position to have the button in the manual for if you have one stompbox or a rack) and ive tried it all out in both postions.

The only way i can avoid this is by having my Pedal directly into the input and having the head on clean, although i want to use the acoustic simulator which the head has and use the marshall footswitch to jump from the acoustic simulator into an effect ready on the Pedal set into a channel on the head.

Extra info:
Ive been using an Ibanez Iceman with the volume on full.
I've only had the master volume on the head during sound testing below 3.
The cable i used running into the FX Return was a bit dodgy, if it was bent at the jack end at a certain point it would fizzle, although im sure it wouldn't have anything to do with it.
Im not sure if my pedal settings had much to do with it, but i set everything i could so it suited the stack using the Output menu.

If you know how i can get a channel on the head with the full sound of my Pedal then PLEASE TELL ME, although any help is appreciated, thanks.
Im not sure how well this would work with a Pod but i used to use my old VAmp2 like this to get the sound solely from that.
Dont have anything plugged in the imput of the amp, insted plug straight into the pod and set the sounds you want on that. Then plug the main output of the pod into the FX return on the amp. This compltely bypasses the Preamp stage of the amp so in theory only the sound of the pod is coming through

Hope this helps