I found a weird "psychological" solution for the threaded connector problem. If you buy a size 000 (less than 1/2-inch outer diameter, the smallest available size) beveled faucet washer, you can file or bore out the inside until it's just wide enough to push down onto the threads and "thread" it on (even though it's unthreaded, just rubber). Of course, you have to swab the filed washer thoroughly inside and out with alcohol and then water to get rid of rubber dust--you wouldn't want that getting in the connector itself. The washer then will be the right inner-diameter and outer-diameter, but will be a little too high, so you can do one of two things. You can rub it back and forth on fine sandpaper until you wear the bottom off (or the top, as you like) and it's the same height as the 7520 connector, or you can try to widen the inner diameter of the part that extends above the 7520's connector when the washer's "threaded" on. In the first case, the top of the washer will then be flush with the end of the connector, and any 1/8" plug will just sit on top. In the second case, you'll have a sort of extended part of the washer that fits tightly around your 1/8" plug housing (provided it's not a really wide one). In either case, it looks a whole lot nicer than having those threads open, and all that space around them where they stick out from the 7520s. And it gets rid of the problem--out of sight, out of mind (hence the "psychological" aspect of the solution). A beveled faucet washer (size 000, sometimes called 1/8 for some unknown reason) is about 20 or 30 cents from Ace Hardware. Home Depot doesn't seem to have this size, and they don't sell them individually anyway. But at Ace they even have a few colors. Here are some pictures of size 000 beveled faucet washers (sometimes called beveled Bibb washers). The black ones in the photo below don't look too nice, but the ones at Ace were beautiful, just like the white ones pictured here, and I swear they look like they're a manufactured part of the 7520s when you put them on. At Ace they have a section of little plastic drawers in the plumbing area, where you can buy just one, like I said 20 cents. Best of all they're faucet washers, so maybe they'll help with any leakage problems you have with your headphones. (ha ha...).
Edited by Darner - 5/12/14 at 8:46am