[Yellowsmiley1]

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.

 

[PurpleAngel]

Quote:

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?)

Personally, I would think 600-Ohm headphone would need a decent AC powered headphone amplifier to sound their best.
Might be best to just spend the cash for nice low Ohm headphones for portable use
 
I've heard the Yamaha RX-371 is rated for up to 450-Ohm headphones and the RX-471 might share a lot of the same guts as the RX-V371.
So maybe test the DT990 Premium 600-Ohm in the Yamaha before committing your cash to a portable amp.

 

[Bill-P]

Most portable amps (except for the Objective 2) are inadequate to drive 600 Ohm headphones. You'll need a desktop amp for that task, and not all desktop amps can accommodate them.
 
But that aside, I'm confused. The current DT990 Pro is 250 Ohm only, no exception. Are we... talking about a very old DT990 Pro?

 

[Yellowsmiley1]

Most portable amps (except for the Objective 2) are inadequate to drive 600 Ohm headphones. You'll need a desktop amp for that task, and not all desktop amps can accommodate them.

But that aside, I'm confused. The current DT990 Pro is 250 Ohm only, no exception. Are we... talking about a very old DT990 Pro?

I'm not sure what year the ones I got are, but they are not too old, you can buy 600 ohm versions on Amazon

 

[proton007]

The basic problem is the amp will reach its gain limit when using a portable power source with 600 Ohm headphones.
So unless you go for a desktop solution (higher input voltage), portable ones will have this issue.

 

[stv014]

The most important thing is to have high enough voltage, and 2x9V batteries would be sufficient (2x12V would be ideal, but if you are not listening to classical music at high volume, the lower voltage can still be fine). Other than that, a 600 Ω headphone is not difficult to drive. The OPA2134, or even a cheaper NE5532 or NJM4580 could drive it well, because only low current is required (less than 20 mA peak for the rated 100 mW power, which is not even reached with a 2x9V power supply). I would avoid exotic or very high speed chips that are more difficult to implement and prone to stability issues.

 

[Yellowsmiley1]

Quote:

Most portable amps (except for the Objective 2) are inadequate to drive 600 Ohm headphones. You'll need a desktop amp for that task, and not all desktop amps can accommodate them.
 
But that aside, I'm confused. The current DT990 Pro is 250 Ohm only, no exception. Are we... talking about a very old DT990 Pro?

Premium vs Pro was messing with my head.  You might be right, I know they are 600 ohm but they might be the premium instead of Pro, not entirely sure (which is kind of embarrassing).  Ill have more information when they arrive on (estimated) Wednesday.  Sorry for the mix up.

 

[PurpleAngel]

Quote:

Premium vs Pro was messing with my head.  You might be right, I know they are 600 ohm but they might be the premium instead of Pro, not entirely sure (which is kind of embarrassing).  Ill have more information when they arrive on (estimated) Wednesday.  Sorry for the mix up.

I do not think the Beyerdynamic makes a DT990 Pro 600-Ohm, just a DT990 Premium 600-Ohm.