Orpheus HEV-90/HE-90

About the Orpheus HEV-90/HE-90

The Sennheiser Orpheus HEV-90/HE-90 is a complete electrostatic headphone system combining the HE 90 over‑ear headphones with the dedicated HEV 90 tube amplifier/DAC. The HE 90 headphones use open‑back, diffuse‑field‑equalized, push‑pull electrostatic transducers with a circumaural fit, specified frequency response of 25 Hz to 75 kHz (‑3 dB) and published extended ranges of 7–100 kHz (‑10 dB) and 14–85 kHz (‑6 dB). Distortion is below 0.01% at 94 dB and below 0.1% at 110 dB, with a maximum sound pressure level of 118 dB and a bias voltage of 500 V. The diaphragms are made from an ultrathin, approximately 1 µm gold‑coated polymer film, and the headphones weigh about 365 g without cable. The HEV 90 is a class‑A push‑pull tube amplifier with an onboard Bitstream (one‑bit) D/A converter, designed to drive the HE 90 directly at up to 400 Vrms without output transformers and with outputs for two HE 90 headphones. It provides switchable analog RCA line inputs and digital coaxial (S/PDIF) and optical TosLink inputs, with a specified frequency response of 10 Hz to 20 kHz (‑0.25 dB), THD of 0.01% at 1 kHz, unweighted S/N ≥ 80 dB, input sensitivity of 400 mV, and input impedance of 10 kΩ. The amplifier weighs roughly 13 kg and measures about 380 × 155 × 340 mm (often quoted as 53 × 34 × 15.5 cm including the marble base), and uses a Carrara marble housing with multiple visible vacuum tubes. The complete Orpheus system was originally introduced around 1991 as a limited‑production flagship and discontinued in the mid‑1990s, with the total run widely reported as extremely small; it is no longer manufactured and is regarded as a reference‑grade, highly collectible headphone system noted for its natural, highly detailed, smooth sound, very wide bandwidth, and exceptionally low distortion.