You're not kidding, these phones like some juice. All my sources with the exception of my PC are amps with headphone jacks or a DAC w/headphone amp. That's why I figured I'd give em a try. It's slightly underpowered with the DAC, but now sounds pretty good. I have the feeling that if I hooked them up directly to the output of my 50 wpc tube amp it would be killer. Efficiency is 98dB and 50 ohms, but with a headphone output it's sort of like driving an inefficient pr of speakers with a little amp. Can a set of phones be hooked up to a regular amp speaker connection? Will the common ground be a problem?
Here's some pics of the modded T50 on the 1000 + page Head-fi thread. Scroll down about 2/3 of the page.
http://www.head-fi.org/t/111193/orthodynamic-roundup/6660I'm not yet finished modding and I'm taking a different approach w/stock enclosure. The top ports are blocked from the inside and the bottom ones have a damper covering them. I removed the damper and used artists modeling clay on the outside to cover all but the bottom port. Then I used the clay to fill in the space on the outside to turn it into a slot loaded port. I also removed the driver from the inner cup and cut away the paper/cloth covering between the driver and your ear. The 840 pads have a similar cloth/paper cover on the inside, that I'll probably remove. I haven't gotten that far. Inside the cup the only thing I'm using is a little bit of Acousta-Stuf. This is dacron stuffing made for speakers, that I have left over. I don't want to reduce the volume of the cup which is a bass reflex enclosure. The all-out mods with wood cups are acoustic suspension or infinite baffle and a different set of mods apply.
After initial break-in, covering the ports revealed the bottom octave which was MIA. Much to my surprise it also helped bring in the top end. I settled on one open port as being the best. These phones have a ton of potential. I checked out my initial mods with Crystal Method among others, and the bottom seemed all there. If you're keeping the stock cups, I'm not sure if all the felt, wool, and stuffing is necessary. I have approx 2g of Acousta-Stuf in there and I think I need slightly less. The plastic enclosure seems pretty rigid and sturdy. The clay on the outside probably damps the cup vibrations. Maybe I'll take some pics, if anybody is interested. Some guy on Head-fi sells kits with wood cups and damping, etc for $200. But I think I need another more efficient set for my PC and $200 would get me a decent set of high efficiency phones. The T50 has a relaxed, natural presentation that's a little different from the "normal" set of cans. I think Fostex took the advice of some modders, cause mine didn't come with all the cloth covering behind the drivers. I never experienced such a dramatic change with break-in (well, possibly a couple of phono carts). After about 14 hrs I thought I would return them. After around 2 days of continual playing hooked up to a receiver, they were sounding pretty good. After covering the bottom ports from the outside, I figured I'd keep em. It's sort of like driving a pr of little Maggies, only on you ears. With very little modding it's like having a big pr of Maggies there.
