Fosi Audio MC331 Hybrid Tube Amplifier

Introduction

Thank you for purchasing the Fosi Audio MC331 Hybrid Tube Amplifier. The MC331 is a 2.0 channel integrated amplifier with vacuum tubes and a built-in DAC. It supports five input modes—Bluetooth, USB, Optical, Coaxial, and RCA—making it compatible with a wide range of audio source devices. The retro VU meter needle dances to the rhythm of the music, providing both visual and auditory pleasure. Equipped with a 3.5mm headphone jack, this device meets diverse listening needs. The tubes can be swapped according to personal preference, and the bass and treble control knobs unlock various sound effects. The included remote control allows for easy and convenient remote operation, making your music journey simple and enjoyable.

Product Overview

Front Panel Features:

• 1 Input Mode Indicators
• 2 5654W Vacuum Tubes
• 3 Tube Covers
• 4 VU Meter
• 5 IR Infrared Interface
• 6 3.5mm Headphone Output
• 7 Treble Knob
• 8 Bass Knob
• 9 Power Switch/Mode Switch/Volume Control

Remote Control Functions:

• 1 Power Switch
• 2 Mute Button
• 3 Volume Up
• 4 Previous Track
• 5 Play/Pause
• 6 Next Track
• 7 Volume Down
• 8 Input Mode Selection
• 9 Bluetooth Mode
• 10 Bluetooth Pairing Reset
• 11 Treble Control
• 12 Bass Control

Rear Panel Features:

• 1 RCA Input
• 2 Bluetooth Antenna Connector
• 3 Optical Input
• 4 Coaxial Input
• 5 USB Input
• 6 DC 19V-24V Power Input
• 7 Pre-Out
• 8 Speaker Output

Specifications

Package Contents

• MC331 Amplifier
• 5654W Vacuum Tube × 2
• Tube Cover × 2
• Bluetooth Antenna
• Remote Control
• 24V/4.5A Power Supply Unit
• User Manual

Operation Guide

1. Install the Bluetooth antenna onto the Bluetooth interface of the MC331.
2. Insert the 5654W tubes into the MC331, ensuring the pins are properly aligned, then attach the covers.
3. Choose the appropriate cable (such as USB, optical, or coaxial) to connect the audio source to the MC331’s audio input interface. Skip this step if using a Bluetooth audio source.
4. Use speaker cables to connect passive speakers to the MC331. If you are using headphones, connect them to the headphone jack on the MC331.
5. Connect the MC331 to the power supply, then long press the main knob for 2 seconds to power on and allow the tubes to warm up for 15 seconds. Short press the knob to switch to the desired input mode (connect to the Bluetooth now if using a Bluetooth device as the source).
6. Before playing music, set the volume to the lowest level. Gradually increase the volume to an appropriate level after playback begins. You can also adjust the bass and treble knobs to achieve your preferred sound effects. All these functions can also be controlled using the included remote control.

Important Notes

• Since the MC331 is a tube amplifier, please make sure to allow a 15-second warm-up time for the tubes before starting playback.
• The USB port is for data transfer only and cannot be used as a power connector.
• Avoid connecting or disconnecting cables while the device is powered on to prevent noise, potential damage to the equipment, and harm to your hearing.

Frequently Asked Questions

1. No sound after connecting the product and powering it on?
   After powering on the MC331, the tubes require approximately 15 seconds to warm up before they begin functioning. If there is still no sound after 15 seconds, please check if the cables are connected correctly, if the tubes are properly inserted, and if the input mode is set correctly.
2. Using a phone as the audio source with USB input mode, all connections are correct, but sound is only coming from the phone?
   Please check if the phone has data transfer mode enabled. Some phone models automatically enable data transfer, while others require it to be manually activated.
3. Can headphones and passive speakers play simultaneously?
   The MC331 defaults to headphone output priority. To use speaker output, you need to disconnect the headphones first.
4. What tube models are compatible for replacement?
   The following tube models are compatible: EF95, 6AK5, 6AK5W, 403A/403B, 6J1, 6J1P, 6J2, 6J3, 6J4, 6J5, among others. You can test and choose based on your personal preference.
   Note: When replacing tubes, ensure that the MC331 is powered off and that the tubes have cooled down to avoid burns or damage to the product.

Warranty and Maintenance

Fosi Audio pledges to give a 24-month limited warranty and support from the date of purchase. If you encounter any problem when using our product, please contact our support team at support@fosiaudio.com.

Warranty Service:

For products purchased through official sales channels, warranty service is provided via mail-in repair. For products purchased through other channels, please refer to the regulations of the sales agent and local national laws regarding warranty.

Conditions not covered by warranty:

• Damage caused by human factors, including but not limited to use in non-normal working environments or failure to follow the instructions in the manual.
• Unauthorized disassembly, modification, or repair by the user.
• Damage caused by using non-specified or unauthorized accessories.
• Inability to provide valid proof of purchase.
• Products not belonging to Fosi Audio.

About Us

Fosi Audio designs and builds innovative audio products with all your music in mind. Great sound, simple but elegant designs, high-quality components, and truly useful features are what Fosi Audio pursues. We sincerely hope you can get as much enjoyment from our products as we’ve had to create them!

Official Website: www.fosiaudio.com

Amazon Store: www.amazon.com/fosiaudio

Facebook Page: www.facebook.com/fosiaudioglobal

Youtube Channel: www.youtube.com/@fosiaudio

Official Forum: https://community.fosiaudio.com

Whatsapp: +86 13716612254

After-Sales Service and Technical Support Email: support@fosiaudio.com

Online Support

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