Nobsound A3 HiFi Bluetooth 5.0 Receiver Tube Amplifier

1. Introduction

The Nobsound A3 is a versatile hybrid tube amplifier designed to enhance your audio experience. It features multiple input options including Bluetooth 5.0, Coaxial, Optical, USB (PC-USB/U-disk), and two groups of Stereo RCA inputs, making it compatible with a wide range of devices such as phones, computers, TVs, CD players, and MP3 players. The amplifier delivers a rated output of 35W+35W, capable of driving most home passive speakers, and includes a 6.5mm headphone jack for high-fidelity personal listening. Additionally, a low-frequency output allows for connection to an active subwoofer, creating a powerful 2.1-channel audio system. Its unique design incorporates 13P1P and 6P16A tubes for a warm, delicate, and smooth sound, complemented by a retro VU meter and a user-friendly remote control. The robust aluminum alloy body helps suppress mechanical vibration and prevent electromagnetic interference.

Figure 1: Nobsound A3 Hybrid Tube Amplifier overview.

2. Safety Information

Please read and understand all safety instructions before operating this device. Keep this manual for future reference.

• Ensure the AC 110V/220V switch on the rear panel is set to the correct voltage for your region before connecting the power cord. Incorrect voltage selection can damage the unit.
• Do not expose this appliance to rain or moisture.
• Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.
• Protect the power cord from being walked on or pinched, particularly at plugs, convenience receptacles, and the point where they exit from the appliance.
• Unplug this appliance during lightning storms or when unused for long periods of time.
• Refer all servicing to qualified service personnel. Servicing is required when the appliance has been damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the appliance, the appliance has been exposed to rain or moisture, does not operate normally, or has been dropped.

3. Package Contents

Please check the package contents upon unboxing to ensure all items are present and undamaged:

• 1x Nobsound A3 Amplifier
• 1x Power Cord
• 1x Remote Control (Note: Batteries are not included. Please prepare 2x AAA batteries for the remote control.)

Figure 2: Included items and product dimensions.

4. Product Overview

4.1 Front Panel

Figure 3: Front Panel Controls and Indicators.

• IR: Infrared receiver for the remote control.
• Power Switch: Toggles the amplifier ON/OFF.
• Input Select Switch: Cycles through available audio inputs.
• Input Channel Indicators: LEDs illuminate to show the currently selected input (COAX, OPT, BT, CD, DVD, USB).
• VU Meter: Displays the audio signal level, providing a visual representation of the sound.
• 6.5mm Headphone Output: Connect headphones for private listening.
• USB Input: For connecting a USB flash drive (U-disk) for music playback.
• Previous/Next Song Buttons: Control track selection during USB playback.
• Volume Knob: Adjusts the overall output volume.

4.2 Rear Panel

Figure 4: Rear Panel Connections.

• SW.OUT (Subwoofer Output): Connects to an active subwoofer.
• INPUT (RCA): Two sets of stereo RCA inputs (labeled CD and DVD) for analog audio sources.
• COAX (Coaxial Input): Digital coaxial audio input.
• OPT (Optical Input): Digital optical audio input.
• Speaker Output (FR/FL): Connects to passive speakers (Front Right/Front Left).
• AC 110V/220V IN: Voltage selector switch and power inlet. Ensure this is set correctly for your region.

4.3 Connectivity Diagram

Figure 5: Example connectivity for various audio sources and outputs.

5. Setup Instructions

Follow these steps to set up your Nobsound A3 amplifier:

1. Power Connection:
   • Locate the AC 110V/220V switch on the rear panel.
   • Toggle it to the correct voltage for your country/region (e.g., 110V for North America, 220V for Europe).
   • Connect the provided power cord to the amplifier's power inlet and then to a wall outlet.
2. Speaker Connection:
   • Connect your passive speakers to the 'Speaker output' terminals (FR for Front Right, FL for Front Left) on the rear panel. Ensure correct polarity (+ to + and - to -).
3. Subwoofer Connection (Optional):
   • If using an active subwoofer, connect its input to the 'SW.OUT' (Subwoofer Output) on the rear panel.
4. Input Source Connection:
   • RCA: Connect analog audio sources (e.g., CD player, DVD player) to the 'INPUT' RCA jacks (CD or DVD).
   • Coaxial/Optical: Connect digital audio sources (e.g., TV, game console) to the 'COAX' or 'OPT' inputs.
   • USB (U-disk): Insert a USB flash drive containing music files into the front panel 'USB' port.
   • PC-USB: Connect your computer to the rear panel USB input (if available, though the front USB is for U-disk).
5. Bluetooth Pairing:
   • Turn on the amplifier and select 'BT' input using the input select switch.
   • On your mobile device, search for Bluetooth devices and select 'Nobsound A3' to pair.

6. Operating Instructions

Once set up, operate your Nobsound A3 amplifier as follows:

1. Power On/Off:
   • Press the 'POWER' switch on the front panel to turn the unit on or off. The tubes will glow when powered on.
2. Input Selection:
   • Press the 'INPUT' switch on the front panel to cycle through the available audio sources (COAX, OPT, BT, CD, DVD, USB). The corresponding LED indicator will light up.
3. Volume Control:
   • Rotate the 'VOLUME' knob on the front panel clockwise to increase volume and counter-clockwise to decrease it.
4. Headphone Usage:
   • Plug your 6.5mm headphones into the headphone jack on the front panel.
   • Important: The 6.5mm headphone output has priority. If headphones are connected, speaker and low-frequency outputs will be muted. Disconnect headphones to enable speaker and subwoofer output.
5. USB (U-disk) Playback:
   • Insert a USB flash drive (up to 128GB) with MP3/WAV/FLAC/APE/WMA files into the front USB port.
   • Select 'USB' input.
   • Use the 'Previous song' and 'Next song' buttons on the front panel or remote control to navigate tracks.
6. Remote Control:
   • The included remote control allows for convenient operation of power, input selection, volume, and USB playback functions from a distance.
   • Ensure batteries are installed (2x AAA, not included).
7. VU Meter:
   • The VU meter on the front panel will visually indicate the audio signal level during playback.

7. Troubleshooting

If you encounter any issues with your Nobsound A3 amplifier, please refer to the following common troubleshooting steps:

• No Sound Output:
  • Check if the amplifier is powered on and the tubes are glowing.
  • Ensure the correct input source is selected.
  • Verify that the volume knob is not set to minimum.
  • If using speakers, ensure headphones are unplugged from the front panel jack.
  • Check all audio cables for secure connections and damage.
  • Confirm speakers are correctly wired to the output terminals with correct polarity.
• Distorted Sound:
  • Reduce the volume from both the amplifier and the source device.
  • Check if the input signal is too strong (overdriving the amplifier).
  • Ensure speaker impedance matches the amplifier's specifications (4-16Ω).
  • Inspect audio cables for damage or poor connections.
• Bluetooth Connection Issues:
  • Ensure the amplifier is set to 'BT' input.
  • Make sure the Bluetooth device is within range (typically 10 meters/33 feet) and not obstructed.
  • Try unpairing and re-pairing the device.
  • Restart both the amplifier and the Bluetooth source device.
• USB (U-disk) Playback Issues:
  • Ensure the USB drive is formatted correctly and contains supported audio formats (MP3/WAV/FLAC/APE/WMA).
  • Check that the USB drive capacity does not exceed 128GB.
  • Try a different USB drive to rule out drive issues.
  • Note: The USB input does not support MAC systems.
• Remote Control Not Working:
  • Ensure fresh AAA batteries are correctly installed in the remote control.
  • Point the remote directly at the IR receiver on the amplifier's front panel.
  • Remove any obstructions between the remote and the amplifier.

8. Specifications

9. Warranty and Support

The Nobsound A3 amplifier comes with a 2-year warranty, ensuring peace of mind regarding product quality and performance.

• Free Returns: Enjoy free returns within 90 days of purchase.
• Fast Delivery Guarantee: The product is eligible for fast delivery. In case of delayed delivery, a $1.00 coupon code may be provided. Refunds are also available if the package is lost or items are damaged during transit, or if no delivery occurs within 30 days.
• Customer Support: For any technical assistance, warranty claims, or further inquiries, please contact the nobsound Official Store directly through the platform where the purchase was made.