I just tried that, didn’t change anything. I also made another observation today. The Pre-Delay knob when turned up produces the delayed guitar sound as it should, but there is also a high pitched screech following that is only consistent in this hall setting. It sounds as if the delayed guitar “cuts out” when the pre delay is high with feedback. Im beginning to think the problem has to do with the pre delayi function because the popping usually comes after the note is hit.