I recently bought a pair of Byerdynamic DT990s Pro 600 Ohm off the sell forums (still shipping), for a pretty decent price. They are going to be my first real set of audiophile headphones. Only issue I'm having is finding a way to power them. For home use I use a RX-v471 AV receiver, which I have heard will do a fine job powering them (http://www.head-fi.org/t/598036/good-headphone-amp-for-home-cinema-use). Now I would like an portable amp I could use with my Android phone (LG Revo) and Ipod Touch. Only amps I could find that could power them were $200+ (Pico series) and I don't really feel up to dropping that kind of money (at the moment).
I looked into making my own (Cmoy) and found it was relatively easy to do (just some simple soldering). I have read a lot of places that the Cmoy design is meant to power "high impedance" headphones, but I'm not sure if they mean to include 600 ohm with that (as I'm pretty sure 600 ohm is quite high). Obviously I won't know if I like it till I can actually test them, but as I really have nothing to compare them too, I won't know if I'm getting all I could get.
Long intro, but the bottom line question I have is, are there any modifications I could make to the CMoy design that would be specifically targeted towards powering the Byer DT990s Pro 600 ohms. I've read some stuff about messing with the cap sizes and resistor ratios, but I haven't seen anything concrete. http://www.jdslabs.com/diy_mods203.php
(PS. I know I'm going to have to use a 18v design instead of the common 9v design, and I have already implemented that. I am also currently using a OPA2134 chip which is a dual channel amp chip, mainly because this is what I had spares of, perhaps using a different chip would be optimal?)
Thanks for the help.