You gotta turn up the Effects knob on the front of the amp. With a MFX, you've probably set your stuff up to be a certain percentage wet and a certain percentage dry. I know I do so I just use the serial loop and I'm done with it. So with the parallel loop you'd turn it up full if this is the case.
The effects knob is so you can run an effect 100% wet through your processor then back into the amp and mix it with the dry signal. Most units allow you to do this within the unit itself. Just another option for people I guess.
If I want a 10% wet reverb on one channel and another with a 15% wet reverb I want that set interally within the MFX unit. I don't want to futz around with a knob on an amp. So Serial Loop for me. Parallel Loop for others.
