Nobsound A3 Hi-Fi Vacuum Tube Amplifier User Manual

1. Introduction

Thank you for choosing the Nobsound A3 Hi-Fi Vacuum Tube Amplifier. This amplifier is designed to deliver a high-fidelity audio experience with the characteristic warmth of vacuum tubes, combined with modern connectivity options. It features Bluetooth 5.0, multiple digital and analog inputs, a dedicated subwoofer output, and an integrated VU meter for visual feedback.

The Nobsound A3 is engineered for audiophiles, offering an expansive soundstage and detailed acoustic reproduction. Its dual 13P1P and 6P16A tubes, along with premium op-amp chips, ensure a rich and dynamic sound. With its versatile input hub and dedicated DAC, it seamlessly integrates with various audio sources, from turntables to streaming devices.

Image 1.1: Front view of the Nobsound A3 Hi-Fi Vacuum Tube Amplifier, showcasing its vacuum tubes and VU meter.

2. Safety Information

• Power Supply: Ensure the amplifier is connected to a power source matching the specified voltage (AC 110V/220V) as indicated on the rear panel. Incorrect voltage can cause damage.
• Ventilation: Do not block ventilation openings. Ensure adequate airflow around the unit to prevent overheating.
• Moisture: Keep the amplifier away from water, moisture, and high humidity environments.
• Heat Sources: Avoid placing the unit near heat sources such as radiators, heat registers, stoves, or other heat-producing appliances.
• Cleaning: Disconnect power before cleaning. Use a dry, soft cloth. Do not use liquid cleaners or aerosol cleaners.
• Servicing: Do not attempt to service this product yourself. Refer all servicing to qualified service personnel.
• Tube Handling: Vacuum tubes can become hot during operation. Avoid touching them directly. Allow the unit to cool down before handling or moving.

3. What's in the Box

Upon unpacking your Nobsound A3 amplifier, please verify that all the following items are included:

• 1x Nobsound A3 Amplifier
• 1x Power Cord
• 1x Remote Control (batteries not included)

Image 3.1: Contents of the Nobsound A3 package, including the amplifier, power cord, and remote control.

4. Product Overview

4.1 Front Panel

Image 4.1: Detailed view of the Nobsound A3 front panel, highlighting various controls and indicators.

• IR Receiver: For remote control signals.
• Input Channel Indicators: LEDs for Coaxial (COAX), Optical (OPT), Bluetooth (BT), CD, DVD, and USB inputs.
• Power Switch: Toggles the amplifier on or off.
• Input Select Switch: Cycles through available audio inputs.
• 6.5mm Headphone Output: For connecting headphones.
• VU Meter: Displays audio signal levels.
• Previous/Next Song Buttons: For USB playback control.
• USB Input: For connecting a U-disk for audio playback.
• Volume Knob: Adjusts the overall output volume.

4.2 Rear Panel

Image 4.2: Detailed view of the Nobsound A3 rear panel, showing all input and output connections.

• AC Power Input: Connects to the power cord. Includes a voltage selector switch (AC 110V/220V).
• Speaker Output: Connects to passive speakers (Left and Right channels).
• Subwoofer Output (SW.OUT): Connects to an active subwoofer.
• Audio Inputs:
  • Optical (OPT): Digital audio input.
  • Coaxial (COAX): Digital audio input.
  • RCA (CD/DVD): Two sets of analog stereo RCA inputs.
  • USB (PC-USB): Connects to a computer for digital audio input.

5. Setup

Follow these steps to set up your Nobsound A3 amplifier:

Image 5.1: Example setup showing the Nobsound A3 amplifier connected to various audio components.

1. Placement: Place the amplifier on a stable, flat surface with adequate ventilation. Ensure there is enough space around the unit for heat dissipation.
2. Voltage Selection: Before connecting the power cord, verify the voltage selector switch on the rear panel is set to your local power supply (AC 110V or AC 220V).
3. Connect Passive Speakers: Connect your passive speakers to the 'Speaker Output' terminals on the rear panel. Ensure correct polarity (+ to + and - to -) for both left (FL) and right (FR) channels.
4. Connect Active Subwoofer (Optional): If using an active subwoofer, connect its input to the 'SW.OUT' terminal on the rear panel.
5. Connect Audio Sources:
   • Bluetooth: No physical connection needed.
   • Optical/Coaxial: Connect your digital audio source (e.g., TV, CD player) to the 'OPT' or 'COAX' input.
   • USB (PC-USB): Connect your computer to the 'USB' input using a USB cable. Note: USB input does not support macOS.
   • RCA: Connect analog audio sources (e.g., CD player, turntable with pre-amp) to the 'CD' or 'DVD' RCA inputs.
   • U-disk: Insert a USB flash drive into the front panel 'USB' port for direct playback.
6. Power Connection: Connect the provided power cord to the AC power input on the rear panel, then plug it into a wall outlet.

6. Operating Instructions

6.1 Power On/Off

Press the 'POWER' switch on the front panel to turn the amplifier on or off. The VU meter and tubes will illuminate when powered on.

6.2 Input Selection

Press the 'INPUT' switch on the front panel to cycle through the available audio inputs (Coaxial, Optical, Bluetooth, CD, DVD, USB). The corresponding LED indicator will light up.

6.3 Volume Control

Rotate the 'VOLUME' knob on the front panel clockwise to increase volume and counter-clockwise to decrease it. You can also adjust the volume using the remote control.

6.4 Bluetooth Pairing

1. Select 'BT' input using the 'INPUT' switch. The Bluetooth indicator will flash.
2. On your Bluetooth device (e.g., smartphone, tablet), search for available Bluetooth devices.
3. Select 'Nobsound A3' from the list to pair. Once connected, the Bluetooth indicator will remain solid.

6.5 USB (U-disk) Playback

Insert a USB flash drive (up to 128GB, formatted with MP3/WAV/FLAC/APE/WMA files) into the front panel 'USB' port. Select 'USB' input. Use the 'Previous Song' and 'Next Song' buttons on the front panel or remote control to navigate tracks.

6.6 Headphone Output

Connect your 6.5mm headphones to the headphone jack on the front panel. Note: The 6.35mm headphone output has priority. If headphones are connected, speaker and low-frequency outputs will be muted. Disconnect headphones to enable speaker and subwoofer output.

6.7 Remote Control

The included remote control allows for convenient operation from a distance. It typically includes functions for power, input selection, volume adjustment, and track control for USB playback.

Image 6.1: Using the remote control with the Nobsound A3 amplifier for convenient operation.

7. Maintenance

• Cleaning: Regularly wipe the amplifier's exterior with a soft, dry cloth. Avoid using harsh chemicals or abrasive materials.
• Dust: Keep the unit free from dust accumulation, especially around the vacuum tubes and ventilation areas. Use a soft brush or compressed air if necessary.
• Tube Care: The vacuum tubes have a finite lifespan. While designed for durability, avoid excessive vibration or impact. If a tube fails, contact Nobsound support for replacement options.
• Storage: If storing the amplifier for an extended period, disconnect it from power and store it in a cool, dry place, preferably in its original packaging.

8. Troubleshooting

• No Power:
  • Ensure the power cord is securely connected to both the amplifier and the wall outlet.
  • Check the power switch on the front panel.
  • Verify the voltage selector switch on the rear panel is set correctly (110V/220V).
  • Test the wall outlet with another device.
• No Sound:
  • Check that the correct input source is selected.
  • Ensure speaker cables are properly connected and polarity is correct.
  • Increase the volume level.
  • If headphones are connected, disconnect them to enable speaker output.
  • Verify the audio source device is playing and its volume is not muted.
• Bluetooth Not Connecting:
  • Ensure the amplifier is set to 'BT' input.
  • Make sure Bluetooth is enabled on your source device.
  • Move your source device closer to the amplifier.
  • Try unpairing and re-pairing the device.
• Distorted Sound:
  • Reduce the volume level.
  • Check audio cables for damage or loose connections.
  • Ensure the audio source is not overdriving the input.
• USB Playback Issues:
  • Ensure the U-disk is formatted correctly and contains supported audio files (MP3/WAV/FLAC/APE/WMA).
  • Check the U-disk for corruption or damage.
  • Verify the U-disk capacity does not exceed 128GB.

9. Specifications

10. Warranty and Support

For warranty information, technical support, or service inquiries, please refer to the official Nobsound website or contact your authorized dealer. Keep your purchase receipt as proof of purchase for warranty claims.