Ferrum OOR, Headphone Amplifier


The Ferrum Oor is a next level headphone amplifier, for the ultimate in personal listening.


When HYPSOS won an EISA award in 2021, Ferrum knew that they were on the right track and went on to follow their dreams of delivering the best possible audio gear they could think of. When they learned OOR was chosen by the honourable EISA members as best Headphone Amplifier of 2022-2023, all their dreams came true. Like HYPSOS, OOR is a ground-up design without precedent, created from a profound exploration of analogue audio in its purest form. Combining understated great looks married with sophisticated power delivery and amplifier technologies, delivering ultra-low distortion, huge dynamics and unrivaled detail. For those who want to go even further in unleashing unheard musicality, OOR is, of course, designed to pair perfectly with the optional HYPSOS Hybrid Power System.

OOR will redefine the category of headphone amplifiers. OOR will drive any headphones effortlessly to the max of their potential, while preserving the essence of the music it amplifies. Ultra low distortion, zero fatigue, huge dynamics and unrivaled detail result in ultimate enjoyment. OOR actually makes something that is very difficult to accomplish, seem like the most natural thing on earth.

“OOR is made by a group of very talented engineers and industrial designers, right in the heart of Poland. They like to refer to Ferrum as “Brand of Brothers”. OOR is their instrument of choice when they need to completely relax and prepare for their next assignment.” Marcin Hamerla Founder and CEO HEM


  • Gain (dB): balanced -4 dB, + 6dB, +16 dB / single ended -10 dB, 0 dB, 10 dB
  • Operation: Fully balanced, proprietary discrete power amp technology
  • Inputs: XLR, RCA, 2.5 mm DC connector centre positive, proprietary 4-pin DC connector
  • Outputs: Balanced 4-pin XLR, 6.35 mm jack
  • Frequency Response:  20 Hz – 100 kHz 0.1 dB
  • Output Power Single Ended: 400 mW into 300 Ω, 2 W into 60 Ω
  • Output Power Balanced: 1.600 mW into 300 Ω, 8 W into 60 Ω
  • THD on balanced output:  0.00011% / -119 dB, 1 mW into 50 Ω;  0.00028% / -111 dB, 100 mW into 50 Ω
  • THD on unbalanced output:  0.00008% / -122 dB, 1 mW into 50 Ω;  0.00028% / -111 dB, 100 mW into 50 Ω
  • Dynamic range: 130 dB (A-weighted)
  • Input Impedance: 94 kΩ
  • Output Impedance Single Ended: 22 Ω on pre-amp
  • Output Impedance Balanced: 44 Ω on pre-amp
  • Output headphones Impedance: < 0.3 Ω
  • Power Consumption: Idle <15 W
  • Power Adapter: 100/240 V AC to 22-30 V DC
  • Dimension (W x D x H) (In/cm): 8.6 x 8.1 x 2.0 inch / 21.7 x 20.6 x 5 cm
  • Weight (kg/lbs): 1.8 kg / 3.97 LBS

Check out our first look unboxing video:


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