Nobsound HiFi 6L6 Valve Tube Amplifier (Douk Audio F5) Instruction Manual

1. Introduction

Thank you for choosing the Nobsound HiFi 6L6 Valve Tube Amplifier, model F5. This Class A single-ended tube power amplifier is designed to deliver a warm, rich, and transparent sound experience for your home stereo system. Featuring high-quality components and a robust design, it is compatible with a wide range of audio sources and passive speakers. This manual provides essential information for the safe and optimal use of your amplifier.

Figure 1: Nobsound HiFi 6L6 Valve Tube Amplifier (Douk Audio F5)

2. Safety Instructions

• Read all instructions carefully before operating the amplifier.
• Keep the amplifier away from water, moisture, and direct sunlight.
• Ensure proper ventilation around the unit. Do not block ventilation openings.
• Do not expose the amplifier to extreme temperatures or humidity.
• Avoid placing heavy objects on top of the amplifier.
• Always disconnect the power cord from the wall outlet before cleaning or servicing.
• Do not attempt to open the amplifier casing. There are no user-serviceable parts inside. Refer all servicing to qualified personnel.
• The vacuum tubes can become very hot during operation. Avoid touching them to prevent burns.
• Ensure the amplifier is placed on a stable, level surface.

3. Package Contents

Please check the package for the following items:

• 1x Nobsound HiFi 6L6 Valve Tube Amplifier (Douk Audio F5)
• 1x 6N1 Tube (pre-amplifier tube)
• 2x 6L6 Tubes (power amplifier tubes)
• 1x Power Cord

Figure 2: Included components and dimensions

4. Product Overview

4.1 Front Panel

Figure 3: Front Panel Controls

• Power Switch Knob: Turns the amplifier ON or OFF.
• Volume Knob: Adjusts the output volume level.

4.2 Rear Panel

Figure 4: Rear Panel Connections

• CD / AUX Input Select Button: Toggles between CD and AUX RCA inputs.
• CD / AUX Input (RCA): Two sets of stereo RCA inputs for connecting audio sources like CD players, phones, MP3 players, TVs, or computers.
• Speaker Output (Banana Jacks): Connects to passive speakers. Supports 8Ω, 4Ω, and 0Ω (common ground) speaker impedances. Ensure correct impedance matching for optimal performance and safety.
• AC IN (Power Input): Connects the amplifier to the main power supply using the provided power cord.

5. Setup Guide

Follow these steps to set up your Nobsound F5 amplifier:

1. Placement: Place the amplifier on a stable, level surface with adequate ventilation around it. Avoid enclosed spaces.
2. Tube Installation: Carefully insert the 6N1 and 6L6 tubes into their respective sockets on the top of the amplifier. Ensure they are seated firmly but do not force them. The 6N1 tube is typically the smaller central tube, and the two 6L6 tubes are larger and flank it.
3. Speaker Connection: Connect your passive speakers to the Speaker Output terminals on the rear panel. Pay attention to polarity (+ to + and - to -) and impedance matching (8Ω, 4Ω, or 0Ω). Use high-quality speaker cables.
4. Audio Source Connection: Connect your audio source (e.g., CD player, phone, computer) to either the CD or AUX RCA input jacks on the rear panel using appropriate RCA cables.
5. Power Connection: Ensure the Power Switch Knob on the front panel is in the OFF position. Connect the provided power cord to the AC IN port on the rear panel, then plug the other end into a suitable wall outlet (AC 220V).

Figure 5: Example desktop setup

6. Operating Instructions

1. Power On: Turn the Power Switch Knob to the ON position. The tubes will begin to glow, indicating the amplifier is warming up. Allow a few moments for the tubes to reach optimal operating temperature.
2. Select Input: Press the CD / AUX Input Select Button on the rear panel to choose the input corresponding to your connected audio source.
3. Adjust Volume: Start with the Volume Knob at its minimum setting. Begin playing audio from your source, then slowly turn the Volume Knob clockwise to increase the sound level to your desired listening volume.
4. Power Off: When finished listening, turn the Volume Knob to its minimum setting, then turn the Power Switch Knob to the OFF position.

6.1 User Tips: Tube Rolling

The Nobsound F5 features a pluggable tube socket design, allowing for 'tube rolling' – the practice of swapping out tubes for different models to alter the amplifier's sound characteristics. You can experiment with compatible tubes to fine-tune the audio to your preference:

• For 6L6 tubes: Compatible alternatives include 6P3P, EL34, 6550, KT66.
• For 6N1 tube: Compatible alternatives include 6H1, ECC85.

Always ensure the amplifier is powered off and completely cooled down before attempting to change tubes. Handle tubes carefully to avoid damage.

7. Maintenance

• Cleaning: Use a soft, dry cloth to wipe the exterior of the amplifier. Do not use liquid cleaners or abrasive materials, as they may damage the finish.
• Tube Care: Tubes have a finite lifespan. If you notice a significant degradation in sound quality or if a tube fails to light up, it may need replacement. Refer to the 'User Tips: Tube Rolling' section for compatible tube types.
• Ventilation: Regularly check that the ventilation openings are not obstructed by dust or debris.
• Storage: If storing the amplifier for an extended period, ensure it is kept in a cool, dry place, protected from dust and extreme temperatures.

8. Troubleshooting

If you encounter issues with your amplifier, please check the following before seeking professional assistance:

9. Specifications

10. Warranty and Support

For any questions, technical support, or warranty inquiries, please contact your retailer or the manufacturer directly. Keep your purchase receipt as proof of purchase.