The Lehmann Audio Black Cube Linear is a high-fidelity headphone amplifier and single-source preamplifier designed to deliver exceptional sound quality for dynamic headphones and serve as a central hub for a single audio source. It is engineered to accommodate a wide range of dynamic headphones, from 30 Ohms to 600 Ohms, by offering switchable gain settings to optimize performance regardless of the headphone's impedance or sensitivity.
Function Description:
The primary function of the Black Cube Linear is to amplify audio signals for headphones, ensuring a clean, powerful, and detailed sound reproduction. It also acts as a single-source preamplifier, allowing users to connect one audio source and route its signal to either headphones, a power amplifier, or active loudspeakers. The unit features two 6.3mm headphone outputs on the front panel, offering different functionalities. Headphone output 1 mutes the line output when a headphone is connected, making it suitable for dedicated headphone listening. Headphone output 2, however, allows simultaneous listening through headphones and loudspeakers, as it does not mute the line output. This flexibility caters to various listening preferences and setups. The device incorporates a volume knob for precise output level adjustment.
Important Technical Specifications:
- Input Impedance: 47 kOhms
- Maximum Gain: Switchable settings of 0dB, 10dB, 18dB, and 20dB, adjustable via switches located underneath the unit.
- Frequency Response: 10Hz (-0.3dB) to 35kHz (-1dB)
- Signal-to-Noise Ratio (SNR): >95dB at 0dB Gain
- Total Harmonic Distortion (THD): <0.001% at 6mW/300 Ohm
- Channel Separation: >70dB/10kHz
- Interchannel Mismatch: <0.3dB with volume at maximum
- Output Power:
- 300 Ohm: 200mW
- 60 Ohm: 400mW
- Output Impedance:
- Line Out: 50 Ohms
- Phones Out: 5 Ohms
- Audio Connectors:
- Neutrik 6.35mm headphone jacks with gold-plated contacts (1x muting for line out, 1x parallel).
- RCA connectors with gold-plated contacts and Teflon isolation for line input and output.
- Mains Connector: IEC receptacle
- Fuse:
- 100V – 120V AC: 630mA slow or T
- 200V – 240V AC: 315mA slow or T
- Power Consumption: <10W with internal regulated low noise power supply
- Dimensions (case only): 280 x 110 x 44mm³
- Weight: Approximately 1.5kg
Usage Features:
The Black Cube Linear is designed for ease of use while providing advanced customization for optimal audio performance.
- Front Panel Controls:
- Power LED: Indicates when the unit is connected to mains voltage, switched on, and ready for use.
- Headphone Output 1: A 6.3mm jack that mutes the rear line output when a headphone is plugged in. Users are advised to turn the volume knob to minimum before connecting headphones to avoid sudden signal peaks.
- Headphone Output 2: Another 6.3mm jack that allows simultaneous headphone and loudspeaker listening, as it does not mute the line output. It is recommended to use headphones of the same type when using both outputs to avoid level discrepancies.
- Volume Knob: Adjusts the output level for both headphones and the line output.
- Rear Panel Controls:
- Line Input (Stereo): RCA connectors for connecting a single audio source.
- Line Output (Stereo): RCA connectors for connecting to a power amplifier or active loudspeakers. This output benefits from the Black Cube Linear's output stage, making it suitable for use as a single-source preamp.
- Power Switch: A toggle switch that disconnects the primary coil of the power supply transformer from the mains voltage. There is no standby mode.
- Fuse Holder: Contains the primary fuse. A spare fuse is also located within the holder. Users must replace fuses with the specified type and rating for their mains voltage.
- Mains Connector: An IEC receptacle for the power cord. The required mains voltage and fuse type are indicated on a sticker underneath the unit.
- Adjustable Gain: The unit features switchable gain settings (0dB, 10dB, 18dB, 20dB) located underneath the chassis. These settings directly affect the active gain of the input stage, allowing users to match the amplifier's output to the sensitivity and impedance of their headphones. It is recommended to choose a gain setting that provides a slightly higher volume than normal listening habits at the maximum potentiometer position, ensuring headroom for lower-level signals and preventing excessively high volume levels. Gain settings are adjusted separately for each channel, and both channels must be set identically to maintain a balanced stereo image. Important: Do not change gain settings while listening to avoid sudden peaks that could damage loudspeakers or hearing.
Maintenance Features:
- Cleaning: Before cleaning the Black Cube Linear, always disconnect the power plug from the AC outlet to prevent electrical shock.
- Internal Access: The unit should not be opened by the user, as it contains hazardous voltages that could cause injury or electrical shock.
- Professional Repair: In case of any abnormality (smoke, smell, noise, physical damage, or water/foreign object ingress), immediately disconnect the power plug and consult a dealer for repair. Continued use under abnormal conditions may result in fire or electrical shock.
- Power Cord: If the power cord is damaged, contact the dealer for a replacement.
- Cable Quality: To achieve the best possible sonic results, using high-quality connecting cables is recommended.
- Contact Maintenance: Regular maintenance includes keeping all connections clean using a quality contact cleaner.
- Long-Term Storage: If the Black Cube Linear will not be used for an extended period (e.g., during vacation), remove the power plug from the AC outlet to prevent potential fire hazards.
Safety Precautions:
The manual emphasizes several critical safety precautions:
- Use an appropriate power cable and ensure it matches the mains voltage.
- Prevent the unit from getting wet or being exposed to moisture, oil, smoke, or steam.
- Do not place heavy objects on the power cord or install the unit on unstable surfaces.
- Avoid placing the unit in direct sunlight or excessively hot environments.
- Do not handle the power plug with wet hands.
- Always hold the plug, not the cord, when removing it from the outlet.
- Disconnect the unit from the AC outlet during thunderstorms.
- Do not attempt to modify the equipment, as this will void the warranty and could lead to fire or electrical shock.
- Turn off all connected devices and set volume levels to minimum before connecting the Black Cube Linear to avoid loud noises that could damage hearing or loudspeakers.
- Always ensure the volume is set to an appropriate level before putting on headphones to prevent hearing damage.
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