Just to add, maximum voltage varying per load should not be much since DX90 has such a low output impedance. For example, if you have a high output impedance and you use a low impedance headphones, you will get much less voltage than much greater impedance headphones.
Also the high output impedance lower the power output to the load.
Also for those folks with BA iems or customs with multiple BA drivers. Keep in mind of the crossovers, which the high output impedance would affect since crossovers have resistors in them. this will change the filter, and mess up what frequency range each driver would output. Moral of the story is, DX90 has very small output impedance, so it's good for multiple BA iems.
Not true. The buf634 has output current protection so will limit current regardless of voltage but that voltage will be greater into higher impedance. Since low impedance loads (more current) tend to be more efficient and high impedance loads less current demanding (more V) it could actually work out well in real world use. I suppose it could get caught out into rare loads but anything below clipping should be great with the DX50. More power doesn't sound better. It just plays louder.
The part about low output impedance not reacting as much to load is correct, below clipping.
Edited by goodvibes - 4/11/14 at 6:08am