1. Introduction
Thank you for purchasing the Douk Audio Nobsound A2 PRO Bluetooth 5.0 Digital Amplifier. This manual provides detailed instructions for the proper setup, operation, and maintenance of your amplifier. Please read this manual thoroughly before use to ensure optimal performance and longevity of the product.
2. Safety Instructions
- Do not expose this device to rain or moisture.
- Do not disassemble the unit. Refer all servicing to qualified personnel.
- Ensure proper ventilation around the unit to prevent overheating.
- Use only the provided power adapter or one with identical specifications (DC 19-35V).
- Keep the unit away from heat sources, direct sunlight, and strong magnetic fields.
- Avoid connecting or disconnecting speaker wires while the amplifier is powered on to prevent damage.
3. Package Contents
Please check the package for the following items:
- Nobsound A2 PRO Digital Amplifier
- Power Adapter (32V/5A)
- Bluetooth Antennas (x2)
- User Manual (this document)
Image: The Nobsound A2 PRO amplifier, power adapter, and two Bluetooth antennas, illustrating the complete package contents.
4. Product Overview
4.1 Front Panel
Image: Detailed view of the amplifier's front panel, highlighting the Power/Mute button, Input Selection button, Volume knob, Bass knob, and Treble knob, along with the working indicator lights.
- PWR/MUTE Button: Press to power on/off or mute/unmute the audio.
- SELECT Button: Press to cycle through input sources: Bluetooth (BT), AUX, RCA.
- Working Indicator: Lights indicate the currently selected input (BT, AUX, RCA) and power status.
- VOL Knob: Adjusts the overall output volume.
- BASS Knob: Adjusts the low-frequency audio level.
- TRE Knob: Adjusts the high-frequency audio level.
4.2 Rear Panel
Image: Detailed view of the amplifier's rear panel, showing the RF antenna connectors, AUX input, RCA L/R inputs, Speaker Output terminals, SUB OUT, and DC 19-35V power input.
- RF (Antenna) Connectors: For attaching the Bluetooth antennas.
- AUX Input: 3.5mm stereo input for connecting devices via an audio cable.
- RCA Input (L/R): Stereo RCA inputs for connecting audio sources.
- Speaker Output: Binding posts for connecting passive stereo speakers.
- SUB OUT: RCA output for connecting an active subwoofer.
- DC 19-35V Input: Power input for the amplifier.
4.3 Internal Components
Image: Diagram illustrating the key internal components of the Nobsound A2 PRO, including the QCC3031 Bluetooth chip, TDA7498E Amp Chip, ESS9012K2M Decoding Chip, TI NE5532 Op Amps, and other circuit elements.
The Nobsound A2 PRO features advanced components for high-fidelity audio:
- QCC3031 Bluetooth Chip: Supports Bluetooth 5.0 with APTX-HD for high-resolution wireless audio.
- TDA7498E Amp Chip: Provides powerful and efficient amplification.
- ESS9012K2M Decoding Chip: Independent decoding chip for improved channel balance and reduced distortion.
- TI NE5532 Op Amps: High-performance operational amplifiers for enhanced sound quality.
5. Setup
5.1 Connecting Speakers
Connect your passive stereo speakers to the Speaker Output binding posts on the rear panel.
- Ensure the amplifier is powered off before connecting speakers.
- Match the positive (+) terminal of the amplifier to the positive (+) terminal of the speaker, and the negative (-) to the negative (-).
- Use appropriate gauge speaker wire. For optimal performance, 14-gauge wire is recommended for runs under 25 feet.
5.2 Connecting Audio Sources
The amplifier supports Bluetooth, AUX (3.5mm), and RCA inputs.
- Bluetooth: Screw the two provided antennas onto the RF connectors on the rear panel.
- AUX Input: Connect your audio device (e.g., smartphone, MP3 player) to the 3.5mm AUX input using a 3.5mm audio cable.
- RCA Input: Connect your audio device (e.g., CD player, TV, PC) to the RCA L/R inputs using an RCA cable.
5.3 Connecting an Active Subwoofer
If you have an active subwoofer, connect it to the SUB OUT RCA port on the rear panel using an RCA cable.
5.4 Connecting Power
Connect the provided power adapter to the DC 19-35V input on the rear panel, then plug the adapter into a wall outlet.
6. Operating Instructions
6.1 Power On/Off and Mute
Press the PWR/MUTE button on the front panel to power on the amplifier. The working indicator lights will illuminate. Press again to mute the audio. Press and hold to power off the unit.
6.2 Input Selection
Press the SELECT button on the front panel to cycle through the available input sources: Bluetooth (BT), AUX, and RCA. The corresponding indicator light will show the active input.
6.3 Volume Control
Rotate the VOL knob clockwise to increase the volume and counter-clockwise to decrease it.
6.4 Tone Control
Rotate the BASS knob to adjust the low-frequency output. Rotate the TRE knob to adjust the high-frequency output.
6.5 Bluetooth Pairing
- Ensure the Bluetooth antennas are securely attached.
- Select Bluetooth input using the SELECT button. The BT indicator light will blink, indicating it is in pairing mode.
- On your audio device (e.g., smartphone), enable Bluetooth and search for available devices.
- Select "Nobsound A2 PRO" from the list of devices to pair.
- Once paired, the BT indicator light will remain solid. You can now play audio from your device through the amplifier.
Image: A smartphone displaying a music player interface, wirelessly connected to the Nobsound A2 PRO amplifier via Bluetooth, demonstrating the dual antenna design and APTX-HD support.
7. Maintenance
- Clean the unit with a soft, dry cloth. Do not use liquid cleaners or aerosols.
- Keep the ventilation openings clear of dust and debris.
- Store the amplifier in a cool, dry place when not in use for extended periods.
8. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No power | Power adapter not connected; power outlet faulty; amplifier off. | Check power connections; try a different outlet; press PWR/MUTE button. |
| No sound output | Incorrect input selected; volume too low; speakers not connected properly; amplifier muted. | Press SELECT to choose correct input; increase volume; check speaker wiring; unmute amplifier. |
| Bluetooth not connecting | Amplifier not in pairing mode; device too far; antennas not attached. | Ensure BT input is selected and indicator is blinking; move device closer; attach antennas. |
| Distorted sound | Volume too high; poor audio source quality; incorrect speaker impedance. | Reduce volume; try a different audio source; ensure speakers are compatible (4-8 Ohm). |
| Humming or buzzing noise | Ground loop issue; interference from other electronics; faulty cables. | Try plugging into a different outlet; move amplifier away from other devices; replace audio cables. |
9. Specifications
- Model: DZ069_US
- Brand: Douk Audio / Nobsound
- Output Power: 130W x 2 (into 4 Ohms)
- Number of Channels: 2.0 (Stereo) with Subwoofer Output
- Input Voltage: DC 19V-35V (Power adapter included: 32V/5A)
- Bluetooth Version: 5.0
- Bluetooth Chip: QCC3031 (supports APTX-HD)
- Amplifier Chip: TDA7498E
- Decoding Chip: ESS9012K2M
- Op-Amps: TI NE5532
- Audio Inputs: Bluetooth, AUX (3.5mm), RCA
- Audio Outputs: Speaker Output (passive stereo), SUB OUT (active subwoofer)
- Mounting Type: Freestanding
Image: The Nobsound A2 PRO amplifier positioned between two speakers and a subwoofer, illustrating its strong output capability of 130W + 130W and its ability to connect to a 2.1 channel system.
10. Warranty and Support
Douk Audio products are designed for reliability and performance. For warranty information or technical support, please refer to the contact details provided with your purchase or visit the official Douk Audio website. Please retain your proof of purchase for any warranty claims.
