PCM179x DAC converter to electrostatic headphones output

[dreamth]

It might look like this subject is not placed at the right section but i thought otherwise.
Heavily inspired by The Art of Electronics, i thought of two variations for a converters that transfer the DAC current into my new model of electrostatic headphones.One was aimed at any 4...8ma dac with no output offset, the other is aimed at PCM179x series dacs that have a significant current offset.
Due to the fact that I'm not the smartest guy on Earth, the only way i could figure how to actually modify the output volume, was to make use of switching series capacitors of different values to load.
In one case , the worst frequency response on 100pf load is -5db at 20khz at half output , which for electrostatic headphones doesn't really matter all that much, but my headphones are about 50pf and i barely have 1.5db loss at max vol.
More on this, i made the simulations at one current for all loads, but i'd optimize the working current(different dac or more dacs/valves in parallel) for stiffer loads.
Next week I'll be starting building it and make the first real life adjustments and better transistors for the job...
The worst THD has no H2 which in real life will be totally different due to valve and speaker construction imbalances, -87db H3(usually -96db at max volume) and -100...108db H3 for lower output.

 

[dreamth]

As i've gone through thousands of modifications last few days i forgot one small error...