I have made some headway for using headphones with this amp. Rather than simply putting a resistor in series with the output of the amp, I made a simple voltage divider. Using this, I am able to use much more of the volume control as I would with speakers, and hum has decreased dramatically. So, now using the planar headphones, I have a better idea of the actual sound of the amp. Recording show up good or bad immediately and no blaming acoustics and such. I will add that the planar headphones do sound like planar speakers in many ways which of course, makes sense. Frankly, I am not the biggest fan of the planar design, but when it comes to headphones, I am finding that nothing is spit at you either. In fact when using the Grado dynamic driver phones, the difference is immediate, much more than before. No doubt, it is to be expected, but too forward of a sound is as bad as not enough detail.

 Here is a shot of the little circuit that makes it all work together.