Orpheus HEV-90/HE-90

About the Orpheus HEV-90/HE-90

The Sennheiser Orpheus HEV-90/HE-90 system consists of the HE 90 electrostatic headphones and the HEV 90 tube headphone amplifier with onboard D/A processor. The headphones feature an open-back, diffuse-field compensated design with push-pull electrostatic transducers. They have a frequency response of 25 Hz to 75 kHz (-3 dB), with extended ranges reported up to 7–100 kHz at -10 dB, and total harmonic distortion below 0.01% at 94 dB. The maximum sound pressure level is 118 dB, and the diaphragm is made from a 1 µm thick gold-coated polymer foil. The HEV 90 amplifier is a class-A push-pull tube amplifier designed to drive the high-impedance electrostatic headphones directly without output transformers. It offers analog RCA inputs and digital coaxial (S/PDIF) and optical TosLink inputs, with a frequency response of 10 Hz to 20 kHz (-0.25 dB), distortion of 0.01% at 1 kHz, and output voltage of 400 Vrms, enough to drive two HE 90 headphones simultaneously. The amplifier weighs approximately 13 kg and measures 53 × 34 × 15.5 cm. The headphones themselves weigh about 365 grams. The system was originally introduced in 1991 with limited production, with additional units produced in 2005. It is no longer manufactured but remains highly sought after. The design includes luxurious materials such as Carrara marble for the amplifier chassis and features eight glowing vacuum tubes. The sound is described as natural, detailed, smooth, with a very wide frequency range and extremely low distortion, offering a musical and unfatiguing listening experience. The system was