If you run rack units in your parallel loop without a Killdry or 100% wet mode, you will get comb filtering as well. My Triple Recto is the same way. Digital pedals that don't have an analog dry-through will have the same issue also.
This site may earn a commission from merchant links like Ebay, Amazon, and others.
Yes. If you put something in a parallel loop you need to set it to kill dry. But using any pedal in series in a mono rig can't result in comb filtering.
He is asking about using a parallel mixer in his loop for his rack unit.
It will work if you can set each effect to 100% wet. It should anyways. My Lexicon MPX-1 is the same way. It doesn't technically have a "Killdry", but you can set the master mix to 100%, and then the mix of each effect to 100%. Then you control how much of the effect you want by the volume of each effect, and the overall mix of the effects chain by the output on the unit, or the mixer send.
Depending on what gear you have, you can fake this to try it. If you have a desktop mixer, these work well for this. I was using one for the last year or so. I put the mixer in the loop and used the aux sends.
I highly recommend perfecting your set up skills (fretwork, truss rod, bridge adjustment, nut slotting) first. I finished building my parts guitar in February of 2020, and finally got it set up the way I like after about a year of (monthlyish) trial and error.
Get a CV70 and put a hotter paf in the bridge (9-12, maybe), with a more correct paf in the neck (8, I think?).
Wanted to go 4U incase I decide to add something later like a power amp, surge proector, etc. 
Learning music is always more impactful than new gear, especially getting the interplay between Fripp/Belew under your fingers.
But I've never seen you play like Robert Fripp?
