Hand-made (D.I.Y.) original electrostatic headphones called "Perun" (by name of pagan Slavic God of thunder and lightning Perun!). They are made of natural materials (ash, alder, lambskin etc.) and sounds very interesting compared to eminent brands.
Perun amp specs are:
The sensitivity is 0.92 V.
The gain is 47 dB (224)
Uneven response at 100 pF, in the range 10-23000 Hz, not more than 0.1 dB
THD at a frequency of 10 kHz and an amplitude of 0.75 of the maximum (300 V) - 0.03% (determined by the 2nd and 3rd harmonics).
There is no degeneration feedback.
Output, differential voltage (peak to peak ) - 600 V.
The polarization voltage (BIAS) is 580 V.
Enjoy the magic of electrostatic sound.