An uncommon way of driving an electrostatic speaker without a transformer is to connect the plates of a push-pull vacuum tube amplifier directly to the stators, and the high voltage supply between the diaphragm and ground. Electrostatics have reduced even-order harmonic distortion because of their push-pull design. They also have minimal phase distortion.
These planar magentic speakers are truly audiophile but at an affordable (sort of) price. Made in a home-garage operation in New Jersey by Greg Takesh (GT of GT Audio Works), and only available direct from him.
The Acorn ESL is available as a full DIY kit requiring the stators to be bonded into the support structure and all electronics assembled onto their circuit boards or as a partially assembled unit where the stators are pre-glued into the support panels and the electronics are assembled and tested.