Nobsound U4 Mini

Nobsound Douk Audio U4 Mini Bluetooth 5.0 Vacuum Tube Headphone Amplifier USB DAC User Manual

Model: U4 Mini (DZ077)

Introdución

The Nobsound Douk Audio U4 Mini is a versatile HiFi audio device designed to enhance your listening experience. It functions as a Bluetooth 5.0 receiver, USB DAC, headphone amplifier, and stereo audio preamplifier. Featuring a classic 6N3 vacuum tube, it delivers a warm, clear, and smooth sound, effectively eliminating harsh digital artifacts. This manual provides detailed instructions for setup, operation, and maintenance to ensure optimal performance.

Características do produto

  • Deseño multifuncional: Combines Bluetooth receiver, USB DAC, headphone amplifier, and preamplifier capabilities in one compact unit.
  • Conectividade versátil: Supports Bluetooth 5.0 and USB audio inputs, with Stereo RCA, 3.5mm AUX, and 3.5mm headphone jack outputs.
  • Vacuum Tube Sound: Incorporates a 6N3 vacuum tube for a warm, clear, soft, and sweet audio signature, ideal for vocals, string instruments, and classical music.
  • Compoñentes de alta calidade: Features QCC3008 Bluetooth chip (supporting APT-X, APTX-LL), TDA1543 decode chip, 2704 USB chip, and MAX9722 headphone ampchip de vida útil.
  • Ampla compatibilidade: USB audio input is compatible with Windows, Mac, Linux systems, and Android smartphones with OTG function, offering plug-and-play convenience without drivers.
  • Powerful Headphone Output: The MAX9722 headphone amplifier provides 300mW output, capable of driving most headphones with impedances from 16 to 600 ohms.

Contido do paquete

Comprobe se o paquete contén os seguintes elementos:

  • 1 x Douk Audio U4 Mini Headphone Ampmáis vivo
  • 1 x 6N3 Vacuum Tube
  • 1 x adaptador de alimentación de 12V
  • 1 x cable USB
  • 1 x Antena Bluetooth

Configuración

  1. Instalación de tubos: Carefully insert the 6N3 vacuum tube into its socket on the top of the unit. Ensure it is seated firmly but do not force it.
  2. Bluetooth Antenna Connection: Screw the provided Bluetooth antenna onto the 'ANT' connector on the rear panel.
  3. Conexión de alimentación: Connect the 12V power adapter to the 'DC 12V' input on the rear panel, then plug the adapter into a power outlet.
  4. Conexión de saída de audio:
    • For speakers or a power amplifier, connect the 'AUDIO OUT' RCA jacks to your audio system using RCA cables.
    • For headphones, plug your 3.5mm headphones into the 'PHONE' jack on the front panel.
  5. Conexión de entrada de audio:
    • Entrada USB: Connect your computer (Windows, Mac, Linux) or Android smartphone (with OTG) to the 'PC-USB' port on the rear panel using the supplied USB cable.
    • Entrada Bluetooth: Ensure the Bluetooth antenna is connected. The device will be discoverable for pairing.
Rear panel connections of the Douk Audio U4 Mini

Image: Rear panel showing 'AUDIO OUT' (RCA/3.5mm), 'PC-USB', 'ANT' (Bluetooth antenna), and 'DC 12V' power input.

USB compatibility with Windows, Mac, Linux, and Android

Image: Illustrates USB compatibility with various operating systems including Windows, Mac, Linux, and Android devices.

Instrucións de funcionamento

  1. Encendido/apagado: Press the 'POWER' switch on the front panel to turn the unit on or off. The vacuum tube will glow when powered on.
  2. Selección de entrada: Use the 'SELECT' switch on the front panel to cycle between USB and Bluetooth inputs. The corresponding LED indicator (USB or Bluetooth) will light up.
  3. Emparellamento Bluetooth:
    • Switch the input to Bluetooth. The Bluetooth LED will blink, indicating it's in pairing mode.
    • On your source device (smartphone, tablet, etc.), search for Bluetooth devices and select "Douk Audio U4 Mini" to pair.
    • Once paired, the Bluetooth LED will remain solid.
  4. Control de volume: Adjust the 'VOLUME' knob on the front panel to control the output level for both headphone and RCA/AUX outputs. Start with a low volume and gradually increase it to a comfortable listening level.
  5. Uso de auriculares: When headphones are plugged into the 'PHONE' jack, the RCA/AUX outputs may be muted depending on the unit's design. Unplug headphones to resume output to speakers.
Front panel of the Douk Audio U4 Mini with controls and indicators

Image: Front panel showing Power switch, Select switch, Phone jack, Volume knob, and Power/USB/Bluetooth indicators.

User enjoying music with headphones connected to the U4 Mini

Image: A user wearing headphones connected to the Douk Audio U4 Mini, demonstrating its headphone ampfunción de eliminación.

Mantemento

  • Limpeza: Use un pano suave e seco para limpar a unidade. Non empregue produtos de limpeza líquidos nin disolventes.
  • Vacuum Tube Care: The vacuum tube can become hot during operation. Avoid touching it. If replacement is needed, ensure the unit is powered off and cooled down before handling the tube.
  • Colocación: Place the unit on a stable, flat surface away from direct sunlight, heat sources, and excessive moisture. Ensure adequate ventilation around the unit.
  • Almacenamento: Se garda a unidade durante un período prolongado, desconéctea da corrente e gárdea nun lugar fresco e seco.

Resolución de problemas

ProblemaCausa posibleSolución
Sen saída de sonUnit not powered on; incorrect input selected; cables loose; volume too low; headphones plugged in (muting RCA/AUX).Check power switch; verify input selection; ensure all cables are securely connected; increase volume; unplug headphones if using RCA/AUX.
Bluetooth non se conectaBluetooth input not selected; antenna not connected; device too far; already paired with another device.Select Bluetooth input; ensure antenna is connected; move source device closer; disconnect from other devices and try pairing again.
Son distorsionadoVolume too high; faulty cables; source audio quality issues; vacuum tube issue.Reduce volume; try different cables; check source audio; ensure vacuum tube is properly seated.
No USB audioUSB input not selected; USB cable faulty; computer/phone not recognizing device.Select USB input; try a different USB cable; check device manager on PC or audio settings on Mac/Android.

Especificacións

CaracterísticaDetalle
Entrada de audioBluetooth 5.0, USB
Saída de audioStereo RCA, 3.5mm AUX, 3.5mm Headphone Jack
Chip BluetoothQCC3008 (supports APT-X, APTX-LL)
Decode ChipTDA1543
Chip USB2704 (supports up to 16bit/96kHz)
Auriculares Amp ChipMAX9722
Relación sinal-ruído (SNR)> 99 dB
Rango dinámico> 99 dB
Potencia de saída de auriculares300 mW
Impedancia dos auriculares16-600Ω
Distorsión harmónica total + ruído (THD+N)0.004% (RL> 10kΩ)
Dimensións (L*W*H)97 * 77 * 32mm (3.82 * 3.03 * 1.26 inches)
Peso unitario250 g
Peso do paquete470 g
Dimensions of the Douk Audio U4 Mini

Image: Diagram showing the dimensions of the Douk Audio U4 Mini in millimeters and inches.

Internal architecture diagram of the Douk Audio U4 Mini

Image: Internal architecture diagram highlighting the MAX9722 (Amp), TDA1543 (Decode), 2704 (USB), and QCC3008 (Bluetooth) chips.

Garantía e soporte

Nobsound products are designed for reliability and performance. For warranty information, please refer to the documentation included with your purchase or contact your retailer. For technical support, please visit the official Nobsound website or contact their customer service department. Please have your model number (U4 Mini or DZ077) and purchase details ready when seeking support.

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