1. Introduction
The Nobsound DA7 is a high-fidelity tube amplifier designed to deliver a rich and warm audio experience. Featuring a combination of 6P1 and 6N1 vacuum tubes, Bluetooth 5.3 connectivity, and a USB input, this integrated amplifier is suitable for audiophiles seeking exceptional sound quality for their home audio systems. Its robust design includes a toroidal power transformer and an imported broadband EI output transformer, ensuring stable and powerful performance. Dual VU meters provide real-time signal monitoring, enhancing the user experience.
2. Safety Instructions
- Always ensure the amplifier is powered off and unplugged before making any connections or performing maintenance.
- Do not expose the amplifier to water, moisture, or excessive heat.
- Ensure adequate ventilation around the unit to prevent overheating, especially around the vacuum tubes.
- Do not open the amplifier casing. There are no user-serviceable parts inside, and doing so may expose you to dangerous voltages.
- Use only the specified power voltage (110V or 220V, depending on your model) to avoid damage.
- Keep out of reach of children.
3. Product Overview
3.1. Front Panel Controls
- Power Switch: Turns the amplifier on or off.
- VU Detection Table: Two analog VU meters that automatically detect and display the signal strength.
- Previous/Play/Pause/Next Knob: Controls playback for USB input (previous track, play/pause, next track).
- Input Select Knob: Selects the audio input source (USB, BT, AUX, CD).
- Volume Control Knob: Adjusts the overall output volume.
3.2. Rear Panel Connections
- Signal Input Terminal (CD IN, AUX IN, PRE OUT): RCA L/R inputs for external audio sources (CD, AUX) and a PRE OUT for connecting to another amplifier or powered subwoofer.
- Audio Output (PRE OUT): RCA L/R output for pre-amplified signal.
- USB Interface: USB 3.0 port for connecting a USB flash drive for digital audio playback.
- Antenna Interface (BT ANT): Connector for the Bluetooth antenna.
- Right Channel Horn Terminal: Speaker output terminal for the right channel.
- Left Horn Terminal: Speaker output terminal for the left channel.
- Power Outlet: AC power input for the amplifier.
3.3. Internal Components & Features
- Vacuum Tubes: The amplifier utilizes four Beijing 6P1 vacuum tubes for the power amplifier stage and three Beijing 6N1 vacuum tubes for the voltage amplifier and push stage, contributing to its characteristic warm and natural sound.
- Bluetooth 5.3: Equipped with an Actions' high-quality decoding chip (ATS2S53), supporting V5.3/5.0/4.2/2.1+EDR for fast, stable, and lossless Bluetooth audio streaming with excellent 24BITDAC processing.
- USB 3.0 Input: Supports USB 3.0 U disks (FAT32, EXFAT file system) up to 128GB (no partition required). Compatible with MP3, WAV, APE, FLAC, AAC, WMA audio formats.
- Toroidal Power Transformer: Specially developed for stable and efficient power delivery.
- EI Output Transformer: Imported broadband EI output transformer for superior audio performance.
- Tube Protection Net Cover: A thickened steel net cover protects the fragile glass tubes and aids in quick cooling and heat dissipation.
- Pure Copper Gold-Plated Interfaces: Ensures better conductivity and convenient, reliable connections for various audio sources.
4. Setup
4.1. Unpacking and Placement
- Carefully remove the amplifier from its packaging.
- Place the amplifier on a stable, level surface away from direct sunlight, heat sources, and moisture.
- Ensure there is sufficient space around the unit for proper ventilation, especially above the vacuum tubes.
- Install the tube protection net cover over the tubes.
4.2. Connecting Speakers
Connect your passive speakers to the Left and Right Channel Horn Terminals (5 and 6 on the rear panel). Ensure correct polarity (positive to positive, negative to negative) and that your speakers' impedance matches the amplifier's output impedance (4Ω or 8Ω).
4.3. Connecting Audio Sources
- CD/AUX Input: Use RCA cables to connect your CD player, DAC, or other analog audio sources to the 'CD IN' or 'AUX IN' RCA ports (1 on the rear panel).
- USB Input: Insert a USB 3.0 flash drive (formatted to FAT32 or EXFAT, max 128GB, no partitions) containing compatible audio files (MP3, WAV, APE, FLAC, AAC, WMA) into the 'USB' interface (3 on the rear panel).
- Bluetooth Antenna: Screw the provided Bluetooth antenna into the 'BT ANT' interface (4 on the rear panel).
4.4. Power Connection
Connect the power cable to the 'Power Outlet' (7 on the rear panel) and then plug it into a suitable AC power supply (110V or 220V, depending on your amplifier's specific model and region).
5. Operating Instructions
5.1. Powering On/Off
Press the 'Power Switch' (1 on the front panel) to turn the amplifier on or off. Allow a few moments for the tubes to warm up after powering on.
5.2. Selecting Input Source
Rotate the 'Input Select Knob' (4 on the front panel) to choose your desired audio source: USB, BT (Bluetooth), AUX, or CD.
5.3. Adjusting Volume
Turn the 'Volume Control Knob' (5 on the front panel) clockwise to increase volume and counter-clockwise to decrease it.
5.4. Bluetooth Pairing
- Select 'BT' using the Input Select Knob.
- On your Bluetooth-enabled device (e.g., smartphone, tablet), search for available Bluetooth devices.
- Select 'Nobsound DA7' (or similar name) from the list to pair. Once paired, audio from your device will stream to the amplifier.
5.5. USB Playback
- Insert your USB flash drive into the USB interface on the rear panel.
- Select 'USB' using the Input Select Knob.
- Use the 'Previous/Play/Pause/Next Knob' (3 on the front panel) to control playback of your audio files.
5.6. VU Meter Function
The two VU meters on the front panel automatically monitor and display the signal strength of the audio passing through the amplifier, providing a visual representation of your music's dynamics.
6. Specifications
| Parameter | Value |
|---|---|
| Model | DA7 |
| Frequency Response | 10Hz~40KHz (-3dB) |
| Harmonic Distortion | 1% (1KHz) |
| Signal-to-Noise Ratio | 85dB |
| Input Sensitivity | 300mV |
| Input Impedance | 100KΩ |
| Output Impedance | 4Ω, 8Ω |
| Supply Voltage | 110V or 220V (model dependent) |
| Power Consumption | 150W |
| Rated Output Power | 12W x 2 (4Ω); 8W x 2 (8Ω) |
| Body Size (H*W*D) | 155 x 318 x 305 mm |
| Net Weight | 7.6 KG |
7. Troubleshooting
- No Power: Ensure the power cable is securely connected to both the amplifier and the wall outlet. Check the power switch position.
- No Sound: Verify that speakers are correctly connected and that the input source is selected. Check volume levels on both the amplifier and the source device. Ensure all cables are securely connected.
- Distorted Sound: Check speaker connections and impedance. Reduce the volume if it's too high. Ensure the audio source is not overdriving the input.
- Bluetooth Connection Issues: Ensure the Bluetooth antenna is attached. Make sure the amplifier is in Bluetooth input mode. Try unpairing and re-pairing the device. Ensure no other devices are actively connected to the amplifier via Bluetooth.
- USB Playback Failure: Ensure the USB drive is formatted to FAT32 or EXFAT and contains supported audio file types. Check that the USB drive is not larger than 128GB and has no partitions.
- Humming/Buzzing Noise: This can sometimes be caused by ground loops. Try plugging the amplifier and source components into the same power strip. Ensure all cables are shielded and in good condition.
8. Maintenance
- Cleaning: Use a soft, dry cloth to clean the exterior of the amplifier. Do not use liquid cleaners or abrasive materials.
- Tube Care: The vacuum tubes have a finite lifespan. While they are protected by a net cover, avoid touching them when hot. If a tube fails, it may need to be replaced by a qualified technician.
- Ventilation: Always ensure the amplifier has proper airflow to prevent heat buildup, which can shorten the lifespan of components.
- Storage: If storing the amplifier for an extended period, disconnect it from power, allow it to cool, and store it in a dry, dust-free environment.
9. User Tips
Note: No specific user reviews or Q&A content were provided for this product. The following are general tips for tube amplifier users.
- Warm-up Time: Allow your tube amplifier a few minutes to warm up after powering on for optimal sound quality. The tubes need to reach their operating temperature.
- Tube Rolling: For advanced users, experimenting with different brands or types of compatible vacuum tubes (known as 'tube rolling') can subtly alter the amplifier's sound characteristics. Always consult a professional before attempting this.
- Speaker Matching: Ensure your speakers are well-matched to the amplifier's power output and impedance for the best performance and to prevent damage.
- Source Quality: The quality of your audio source (e.g., high-resolution digital files, good quality DAC) will significantly impact the overall sound experience.
10. Warranty and Support
For warranty information, technical support, or service inquiries, please contact the seller or manufacturer directly. Keep your purchase receipt as proof of purchase.