Headphones / Earphones
Headphone Amps
DAC built-in headphone amplifiers
Fosi Audio/MC331 Vacuum Tube Integrated Amplifier with DAC

Fosi Audio / MC331 Vacuum Tube Integrated Amplifier with DAC

The MC331 is an all-in-one DAC/amplifier that is compact, powerful, and offers flexible setup options.

【All-in-One DAC & Amplifier】
・The Fosi Audio MC331 integrates a DAC, amplifier, preamplifier, and headphone amplifier into a single unit. It features a remote control for easy switching between audio sources, ensuring a seamless and rich listening experience.

【A Striking Combination】
・As an integrated vacuum tube DAC/amplifier equipped with a VU meter, the MC331 combines the visual appeal of 6J1 vacuum tubes and a VU meter—adding a warm, mellow quality to the sound while infusing a retro aesthetic into its modern design.
*Note: While the product images may show 5725W vacuum tubes, the unit now comes with 6J1 vacuum tubes.

【Flexible Setup Options】
・Supporting Bluetooth, USB, coaxial, optical, and RCA inputs, the MC331 is compatible with a wide range of sources—such as computers, smartphones, CD players, and turntables with built-in phono preamps—allowing for versatile system configurations.

【Compact yet Powerful】
・Despite its space-saving desktop footprint, the MC331 delivers a maximum output of 105W x 2 (@ 4Ω), capable of effectively driving bookshelf speakers. It also includes a pre-out and a 3.5mm headphone output for added versatility.

【User-Friendly Design】
・The MC331 comes with a remote control, allowing you to adjust bass and treble settings from the comfort of your listening chair. The swappable tube design enables you to customize the sound signature to suit your personal preferences.

Important Notes:
① When installing the vacuum tubes, use a suitable tool (such as tweezers) to adjust the alignment of the socket pinholes, ensuring a proper connection with the tube pins.
② If you experience uneven volume levels (e.g., one side louder than the other), it may be due to poor contact or oxidation on the tube pins. We recommend cleaning the pins and reinserting the tubes. ③ When the power is on, the vacuum tubes will remain lit. If noise occurs, it may be due to an issue with the audio source, power supply, wiring, or speakers. We recommend testing each component (audio source, cables, and speakers), checking for power supply interference, ensuring the tubes are securely seated, and allowing the unit to fully warm up for 10–15 minutes.

■ Channels: 2.0
■ Inputs: RCA, Bluetooth, USB, Optical, Coaxial
■ Outputs: Front output (no pre-out), 3.5mm headphone output
■ Amplifier Chip: TPA3221
■ Signal-to-Noise Ratio (SNR): ≥100dB
■ Dynamic Range: ≥100dB
■ THD: ≤0.03%
■ Terminal Impedance: 4–8Ω
■ Maximum Output Power: 105W × 2 @ 4Ω
■ Frequency Response: 20Hz–20kHz (±1dB)
■ Headphone Impedance: 32–300Ω
■ Voltage Range: DC 19–24V
■ Sampling Rate:
・USB: 24-bit/96kHz
・OPT/COA: 24-bit/96kHz
■ Bluetooth Effective Range: ≥10 meters
■ Bluetooth Codecs: SBC, AAC