05. July 2021 · Comments Off on Ferrum OOR Headphone Amplifier · Categories: Hifi News · Tags: , , , , ,


Ferrum is a polish HiFi brand, manufactured by HEM, whose first product was the HYPSOS power supply, which we have just reviewed.

The Ferrum OOR Headphone Amplifier is 100% analogue and the brand say it “will drive any headphone to the max of its capabilities”.

Ferrum OOR Headphone Amplifier

The Ferrum OOR Headphone Amplifier


Ferrum has a design language of ‘keeping it simple’ and as such, the Corten steel and anodized aluminium OOR only needs three knobs on the front panel to control the music. One for gain settings to match your headphones, be it over-ear or in-ear, one to choose between balanced or unbalanced input and the most prominent one for controlling the volume.

Ferrum OOR Headphone Amplifier

The Ferrum OOR Headphone Amplifier rear panel


A great deal of attention was given to the design of the internal power supply, which is fed by the included and specially selected AC/DC power adapter. The Ferrum OOR is a truly balanced design of preamplifier stage coupled with their proprietary discrete power amp technology in combination with the implementation of selected components.

The Ferrum OOR can be upgraded even further using the Ferrum HYPSOS Hybrid Power System together with the proprietary Ferrum Power Link (FPL) connection.

Ferrum OOR Headphone Amplifier

Ferrum OOR Headphone Amplifier and HYPSOS Power Supply


Gain (dB):                                   balanced -4dB, +6dB, +16dB

single ended -10dB, 0dB, 10dB

Operation:                                  Fully balanced, proprietary discrete power amp

Inputs:                                        XLR, RCA

2,5mm DC connector centre positive

proprietary 4-pin DC connector

Outputs:                                     Balanced 4-pin XLR

6,35 mm jack

Frequency Response:                           20Hz – 100kHz 0,1dB

Output Power Single Ended:                  400mW into 300Ω, 2W into 60Ω

Output Power Balanced:                        1.600mW into 300Ω, 8W into 60Ω

THD:            < 0,0003% / -110dB, 100mW into 50 Ohm

on balanced output

Input Impedance:                                  94kΩ

Output Impedance Single Ended: 22Ω on pre-amp

Output Impedance Balanced:                 44Ω on pre-amp

Output Impedance Headphones:            < 0,3Ω

Power Consumption:                             Idle <15W

Power Adapter:                                     100/240V AC to 22-30V DC

Dimension (W x D x H cm/in):                21,7 x 20,6 x 5 cm / 8.6 x 8.1 x 2.0 inch

Weight (kg/LBS):                                   1,8 kg / 3,97 LBS


Founded more than twenty years ago in Warsaw, Poland by Marcin Hamerla, HEM set out to operate at the forefront of audio technology. Having done several projects for the Polish government, HEM’s focus shifted to digital technology in collaborating with Mytek Digital. Experimenting with hi-res audio and Master Quality Authenticated files in particular, HEM manufactured  Digital to Analogue converters under the Mytek brand. Apart from being responsible for manufacturing Mytek, HEM distributed the brand in European and Far Eastern markets. Another brand in HEM distribution is Clarus Cable. HEM recently introduced a new and completely in-house developed brand of HiFi products under the name Ferrum.


1,995 EUR/USD

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