This was previously for sale but deal fell through. Same as http://store.hifiman.com/index.php/he-adapter.html If you're headphone has 4-pin XLR, you can use this adapter to drive your headphone with a power amp's speaker taps. For power hungry headphones, this is an excellent option to drive your headphones. This works well with HE-6 and HD800. I just don't need this anymore. Selling adapter in excellent condition. Price is $65 shipped within CONUS. PayPal extra.