I’m afraid I don’t really understand your description, but:
1) Mr baron58 is correct on the H9 levels – some effect loops are too hot and will overdrive it. The H9 is designed to be used at guitar level.
2) If you (as you imply) are using a parallel effect loop, you should usually have KILLDRY on to avoid the sort of feedback you describe. But, this will cause problems if you have more that one pedal in the loop. No solution to this – it is the nature of parallel loops.
1) I’ve already answered to baron58 🙂
2) Let’s put it like this: The H9 is set in Pre/Post and it’s the only pedal in all the chain. My signal is: guitar— h9(in1-out1)—amp input; Amp Fxloop–h9(in2-out2)–Amp Fxloop. Now: I want to use the amp distortion and use the digital delay on amp’s distorted signal in Fx loop, thus I need the delay set in Post in the fx loop. Sometimes I want to use the Sculpt alogirthm, which goes in Pre in the input of the amp. The problem is that when I use the delay on the distortion of the amp I get the noises.
This happens even if I set the fx loop in serial (So without a line control) with the killdry OFF, and even if I set the fx loop as parallel with the killdry ON, as it should be to avoid feedbacks.
