Or a conventional push-pull output transformer could be used in a para feed arrangement where a choke loads the output tube and a capacitor couples the plate to one end of the primary of the push-pull transformer, while its center tap goes to ground.

   The sound was somewhat noisy, which does not make a lot of sense I know, as the balanced nature electrostatic headphones should cancel all common mode noise, but it does not do so perfectly in practice. Asides from being noisy, the sound was supremely better, more extended and more open sounding than the sound achievable from the step-up transformer that came from manufacturer. (At the time, I used a  big solid-state 200 watt per channel amplifier just to drive my headphones, as nothing else could make them dynamic sounding enough for me!)
   My Stereo 70 could have been converted into a electrostatic headphone amplifier by replacing the EL34's with 6SL7's and 6SN7's. Basically, the amplifier would then consist of a Williamson amplifier without the output tubes! The 6SL7 would provide the first stage amplifier and second stage Split-Load phase splitter. The 6SN7 would provide the Differential amplifier whose plates would connected to the output transformer's primary. The stators would be capacitor coupled to the plates as well. The secondary would find a 100 ohm resistor to load the 6SN7's adequately. The circuit board that normally housed the input circuit could be replaced with additional power supply capacitors. While this conversion was never made, maybe it should have been. One fear was that the output transformer's primary inductance may have proven inadequate for low frequency reproduction. Furthermore, I had just discovered one of the best audio magazines in the world: the Japanese magazine MJ Stereo Technic and it led me in another direction.

OTL Push-Pull Amplifier
   In 1986's fourth issue of MJ Stereo Technic two circuits for driving Stax electrostatic headphones were displayed. Both used cascading Differential amplifiers to provide sufficient gain with 5692's and RCA 10's as output tubes.

Singe triode driving a conventional high-ratio output transformer wired backwards in a para-feed configuration. 

   No matter which topology is chosen, one problem will remain: noise. As the natural noise reduction that results from balanced push-pull operation is not available in the single-ended amplifier, the problem of power supply noise will need extra attention.

Transformer Push-Pull Amplifiers
  This is the easier approach, as the electrostatic headphones are push-pull by design. My first experiment with a push-pull amplifier was with a Dynaco ST-70. The headphones were from Signet and were different from most electrostatic headphones in that the diaphragm came pre-polarized. Apparently, the film is made with a high voltage charge applied to the metal drum that receives the polymer spray and when the film is peeled off, it retains the polarization of its molecules in the absence of the charge. This eliminates the need for a polarizing power supply. Consequently, I was able to connect the stators to the plates of the EL34's directly. CAUTION:  THIS IS VERY DANGEROUS AND NOT AT ALL RECOMMENDED. (Only a rabid audiophile would be willing to put his head in between 430 volts in the pursuit of better listening.)

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