Tony this information is very informative. Thank you. I just recently purchased a dd1 and i have temp set up in my vehicle and have a pos HLC in it and i experienced the problem you explained, with perpetual distortion at any level at 40hz. This question might be against forum rules as the answer might be construed as bashing, but do know if Audiocontrol uses these "transformers" specifically the LC2i? I could be foolish in assuming it would not since its a powered device, but im no expert. Thanks