I made mine with a 12" length of 16 ga high quality copper, nothing fancy just pure, on which I shunted a 100uH choke from Radio Shack. After many, many experiments, this worked the best. The choke was a suggestion from someone here instead of the wire loop, the wire loop of course originated with BudP, and then you said more iron is better, so I combined them all and darned if it didn't work better than any of the other configs. All of the other attempts made a difference for better or worse, but this was the only one that sounded like the testimonials, dramatic improvements in imaging, timbre, and soundstaging.