1.995,00 €–2.985,00 €Price range: 1.995,00 € through 2.985,00 €
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. Zero 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.
EISA Award-Winning Fully Balanced Headphone Amplifier | Up to 8W Output | Discrete Analogue Design | HYPSOS Compatible
The Ferrum Audio OOR Headphone Amplifier is a high-end, fully balanced analogue headphone amplifier and preamplifier designed for demanding music enthusiasts and reference headphone systems.
Developed by Ferrum Audio in Poland, OOR combines proprietary discrete power amplifier technology, exceptionally low distortion, substantial output power and carefully engineered analogue circuitry in a compact, elegant chassis.
Delivering up to 8 watts into 60 ohms through its balanced headphone output, Ferrum OOR is designed to drive a wide selection of dynamic and planar magnetic headphones, including demanding high-end models.
Its performance and engineering received international recognition with the EISA Headphone Amplifier Award 2022–2023.
OOR operates as a complete headphone amplifier using its supplied external DC power adapter, while offering an upgrade path through the Ferrum HYPSOS Hybrid Power System and proprietary Ferrum Power Link.
Available through Chameleon Audio, Ferrum OOR is a compelling choice for audiophiles seeking powerful, transparent and versatile analogue headphone amplification.
Ferrum OOR: Award-Winning Headphone Amplification
EISA Headphone Amplifier 2022–2023
Ferrum OOR was recognised by the Expert Imaging and Sound Association with the prestigious EISA Headphone Amplifier 2022–2023 award.
Following the earlier EISA recognition of Ferrum HYPSOS, OOR demonstrated the manufacturer’s commitment to developing specialist high-end audio electronics.
Its fully analogue design combines substantial power reserves with low distortion and flexible operation.
The amplifier is suitable for high-quality desktop listening systems as well as dedicated headphone installations featuring separate DACs and digital transports.
Engineered in Poland by Ferrum Audio
OOR was created by the engineers and industrial designers behind Ferrum Audio and HEM, drawing upon the company’s experience in professional and high-end audio electronics.
The manufacturer developed the amplifier from the ground up, focusing on analogue circuit design, carefully controlled output transistor operation and efficient power delivery.
Ferrum describes its development team as a close-knit group of specialists sharing a commitment to high-quality music reproduction.
Marcin Hamerla, Founder and CEO of HEM, has highlighted the engineering and design team behind the OOR as central to the product’s identity.
Fully Balanced Analogue Signal Architecture
The Ferrum OOR Balanced Headphone Amplifier uses a fully balanced analogue amplification architecture.
Balanced XLR input signals are processed through the balanced signal path, while incoming unbalanced RCA signals are converted into a balanced internal signal arrangement.
This design gives owners flexibility when connecting different external DACs and analogue audio sources.
The amplifier also offers balanced and single-ended headphone outputs, allowing suitable headphones to be connected through their corresponding cables.
As a fully analogue amplifier, OOR does not incorporate a DAC, USB audio input or network streaming system.
Balanced and Unbalanced Connectivity
Ferrum OOR provides balanced XLR and unbalanced RCA analogue connections for integration into a wide range of hi-fi systems.
The rear panel also provides balanced XLR and unbalanced RCA preamplifier outputs for connection to compatible power amplifiers or active loudspeakers.
The amplifier can therefore act as both a dedicated headphone amplifier and an analogue preamplifier.
Its compact design makes it particularly suitable for systems where a single high-performance analogue control component is preferred.
Ferrum Analogue System Connectivity
Related Ferrum ERCO connection image retained from the original page. The OOR also offers XLR and RCA analogue connectivity, but its physical rear-panel layout is different.
Powerful Balanced Headphone Output
One of the defining characteristics of the Ferrum Audio OOR Headphone Amplifier is its substantial output power.
Ferrum specifies the following headphone output ratings:
Balanced output into 60Ω: 8W
Balanced output into 300Ω: 1.6W
Single-ended output into 60Ω: 2W
Single-ended output into 300Ω: 400mW
The balanced headphone connection uses a four-pin XLR socket, while the single-ended output uses a conventional 6.35mm headphone socket.
These output capabilities make OOR particularly interesting for users of demanding planar magnetic and dynamic headphones.
However, headphone compatibility should always be evaluated using the actual headphone impedance, sensitivity and manufacturer’s recommendations.
Designed for Demanding Planar Magnetic Headphones
High-end planar magnetic headphones can place significant demands on an amplifier’s voltage and current delivery.
Ferrum OOR has been designed with the output power and analogue control required for many of these applications.
Models such as the HiFiMAN Susvara and Abyss AB-1266 are among the demanding headphone designs referenced within Ferrum’s compatibility discussions.
The appropriate gain and listening volume should always be selected carefully, especially with highly sensitive headphones.
OOR is not designed to drive electrostatic headphones that require a dedicated electrostatic energiser or amplifier.
Selectable Headphone Gain
The Ferrum OOR provides three gain settings for both balanced and single-ended headphone operation.
Balanced Headphone Gain
-4dB
+6dB
+16dB
Single-Ended Headphone Gain
-10dB
0dB
+10dB
These selectable gain settings allow users to adapt the amplifier to headphones with different sensitivities and impedance characteristics.
For sensitive headphones, a lower gain setting can offer a more practical usable volume range.
For more demanding headphones, higher gain settings may be appropriate depending on the input signal level.
Proprietary Discrete Power Amplifier Design
The OOR output stage uses Ferrum’s proprietary discrete transistor amplification technology.
The manufacturer developed the circuit to achieve high output power, fast signal response and extremely low measured distortion.
Careful control of the output transistors is an important aspect of the design.
The output stage is engineered to maintain appropriate transistor operating conditions and reduce unwanted distortion during dynamic audio reproduction.
This approach is intended to combine high power delivery with the precision expected from a reference headphone amplifier.
Exceptionally Low Distortion
Ferrum publishes remarkably low total harmonic distortion figures for the OOR.
At 100mW into 50Ω, the specified distortion is approximately 0.00028% for the balanced output under the manufacturer’s measurement conditions.
The amplifier also provides a published 130dB A-weighted dynamic range.
Its wide frequency response and low distortion are designed to preserve fine musical details without introducing significant unwanted coloration.
Wide Frequency Response
The Ferrum OOR offers a published frequency response of 20Hz to 100kHz within 0.1dB.
This extended bandwidth reflects the manufacturer’s wideband analogue circuit design.
The result is an amplifier engineered for accurate transmission of audible frequencies without relying on exaggerated frequency response characteristics.
Ferrum HYPSOS Power Supply Upgrade
Designed to Work with Ferrum HYPSOS
The Ferrum OOR is supplied with a carefully selected external DC power adapter, allowing it to operate as a complete headphone amplifier.
For an optional upgrade, the amplifier can be paired with the Ferrum HYPSOS Hybrid Power System.
HYPSOS provides an advanced regulated DC power supply architecture with four-terminal voltage sensing.
The connection uses Ferrum’s proprietary Ferrum Power Link (FPL) system.
The dedicated FPL cable is available separately unless included in a selected bundle package.
Ferrum Power Link uses a dedicated four-wire connection between a compatible HYPSOS power supply and OOR.
Two conductors deliver DC power while another two conductors provide voltage sensing feedback.
This arrangement helps HYPSOS regulate voltage at the connected component, compensating for electrical losses along the cable within its operating limits.
The system is designed to provide stable power delivery as the amplifier’s electrical demands change.
Audible improvements from a power supply upgrade remain dependent on the connected system and listening conditions.
Use Ferrum OOR as a Stereo Preamplifier
In addition to its headphone amplification capabilities, OOR includes analogue preamplifier functionality.
The rear XLR and RCA line outputs can connect to compatible stereo power amplifiers or active loudspeakers.
The front-panel volume control also controls the analogue line output level during normal preamplifier operation.
This makes OOR suitable for users who want a single analogue component for both high-end headphones and a compact speaker-based system.
Volume Bypass Function
Ferrum provides a bypass setting that disables the OOR’s internal volume potentiometer.
This function is intended for systems where output level is controlled safely by another component.
Important: Bypass operation can send a high-level signal to connected headphones or downstream amplifiers. The source volume must be reduced and the system configuration checked before activating this mode.
Simple and Intuitive Front-Panel Controls
The OOR front panel features three primary rotary controls.
These provide straightforward operation for input selection and power, headphone gain selection and volume adjustment.
The front-panel Ferrum logo illumination can also be adjusted according to the user’s preference.
The understated mechanical design reflects the company’s preference for functional, minimalist audio equipment.
Ferrum OOR is designed for use with a broad selection of dynamic and planar magnetic headphones.
Its high balanced output power, low headphone output impedance and selectable gain settings provide considerable flexibility.
Choosing the correct connection and gain setting is particularly important when using sensitive headphones or very demanding low-sensitivity models.
For electrostatic headphones, a dedicated compatible electrostatic amplifier or energiser is required.
Why Buy from Chameleon Audio?
At Chameleon Audio, we specialise in high-end audio systems, reference headphone amplification and carefully selected digital and analogue equipment.
Free Worldwide Shipping with Full Transport Insurance
All brand-new products purchased from Chameleon Audio include FREE SHIPPING WITH FULL TRANSPORT INSURANCE.
Your high-end audio equipment is carefully packed and insured during transportation for additional peace of mind.
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Ferrum OOR is a high-end, fully balanced analogue headphone amplifier with dedicated preamplifier functionality and proprietary discrete output stages.
How much power does Ferrum OOR deliver?
OOR delivers up to 8W into 60Ω through its balanced headphone output, with other ratings depending on load impedance and connection type.
Does Ferrum OOR have a balanced headphone output?
Yes. It provides a four-pin XLR balanced headphone output and a 6.35mm single-ended headphone output.
Can Ferrum OOR drive HiFiMAN Susvara headphones?
Ferrum identifies the Susvara among the demanding planar magnetic headphones suitable for consideration with OOR. Actual performance depends on listening volume, recording level and system configuration.
Can OOR drive electrostatic headphones?
No. Conventional electrostatic headphones require specialised amplification and cannot be connected directly to the OOR headphone outputs.
Does Ferrum OOR include a DAC?
No. OOR is a fully analogue amplifier and requires an external DAC or another suitable analogue source.
Does OOR have balanced XLR inputs?
Yes. It provides balanced XLR and unbalanced RCA analogue input connections.
Can OOR be used as a preamplifier?
Yes. OOR includes balanced XLR and unbalanced RCA line outputs, allowing connection to compatible power amplifiers and active speakers.
Does OOR support adjustable gain?
Yes. Three gain settings are provided for both balanced and single-ended headphone connections.
Can I use Ferrum HYPSOS with OOR?
Yes. OOR supports a compatible Ferrum HYPSOS power supply through Ferrum Power Link and the appropriate connection cable.
Is HYPSOS included with OOR?
OOR is supplied with its standard external DC power adapter. HYPSOS is an optional separate product unless included in a selected bundle.
What is Ferrum Power Link?
Ferrum Power Link is a proprietary power connection that supports four-terminal voltage sensing when used with a compatible HYPSOS power supply.
Does OOR have a volume bypass function?
Yes. However, bypass mode must be used carefully because it disables the internal volume control and can result in dangerously high output levels.
Has Ferrum OOR won an EISA award?
Yes. Ferrum OOR received the EISA Headphone Amplifier 2022–2023 award.
Where can I buy the Ferrum OOR Headphone Amplifier?
Ferrum OOR is available through Chameleon Audio with advice on headphone matching, system integration and optional HYPSOS power supply configurations.
The Ferrum Audio OOR Headphone Amplifier combines a fully balanced analogue architecture, proprietary discrete output amplification, selectable gain and substantial power reserves in a compact high-end component.
With its EISA recognition, dedicated preamplifier functionality and optional HYPSOS power supply upgrade, OOR offers a flexible solution for reference headphone listening systems.
Contact Chameleon Audio for headphone compatibility, Ferrum OOR availability, HYPSOS bundle options and international delivery.
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Specifications
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
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