I use 10 ft extension cables with my Audeze LCD-X headphones, Shure SRH-1540 headphones, and Shanling IEMs, and had detected zero added noise with any of them. I think only a VFD, a big motor, or a microwave oven, would introduce noise in most households. It is correct that balanced is preferable for long cable runs if there's added noise associated with this, but it's meant for a studio environment where there's lots of electronics around. I just don't happen to run my cables by things that would introduce much of it. Though balanced does offer you more power, I don't buy the extended dynamic range argument, unless you had been severely underpowering your headphones with the single ended configuration (like 30 mW with those headphones). If you're listening music that doesn't have a lot of low end, you won't need as much power as you would with rock or techno music. I've lived in Ontario, Alberta, California, and Texas (in that order). In all four places I had used Digikey to buy mail order electronics parts. That's probably your best bet, on the "rock". I think I have a four pin balanced headphone connector in storage from 2018, in the same box as my variable heat Weller soldering iron. I had decided not to continue making a homemade cable. I just feel that the marketing people have been overselling the benefits of balanced headphone connections (and that salesman had HiFiMan HE-1000s). I also don't use balanced patch cables (my bulk has three conductors and a foil shield, with which I could make XLRs or RCAs). The professional microphones at Guitar Center where I had gone today, all had XLR connections, because you are more likely to pick up noise in a lower voltage situation.
I'm trying to sell my SRH1540s and wish I had gotten SRH940s instead, for their resolution and foldability. Neither of them can match Audeze bass (but then again, they're less than half the price). My $500 IEMs can out-resolve even the LCD-X, but they have imaging, soundstage and timbre problems. But still, I am likely to take those on a trip.
