The Fosi Audio MC331 is a hybrid tube integrated amplifier with a built-in DAC, two 5654W tubes and a VU meter, rated up to 105W × 2 @ 4Ω and taking Bluetooth, USB, optical, coaxial and RCA sources. It suits desk or shelf systems with 4–8Ω bookshelf speakers, plus headphones on its 3.5mm output.
Who the Fosi Audio MC331 is for
Bookshelf speakers: Rated up to 105W × 2 @ 4Ω for 4–8Ω speakers, it drives a pair of passive bookshelf speakers from its speaker terminals.
Many sources, one box: Bluetooth, USB, optical, coaxial and RCA inputs cover a computer, phone, TV, CD player or a turntable with a built-in phono preamp.
2.1 setups: The pre-out connects a powered subwoofer for a 2.1 system, per Fosi.
Retro desk looks: Two 5654W tubes and a VU meter set the look, and the remote switches inputs and adjusts bass and treble from your chair.
Skip it if: Your speakers dip below 4Ω or you want aptX or LDAC; Fosi rates the MC331 for 4–8Ω loads and lists SBC and AAC for Bluetooth.
Fosi Audio MC331 key specs
Type: Hybrid tube integrated amplifier with built-in DAC and headphone amp
Max output power: 105W × 2 @ 4Ω (Fosi max rating)
Inputs: Bluetooth (SBC, AAC), USB, optical, coaxial, RCA
Tubes: 2 × 5654W (type may vary by batch); Fosi lists 6AK5, 6AK5W, 6Zh1P, 6J1, EF95 and other 7-pin tubes as compatible
Speaker impedance: 4–8Ω
THD / SNR: ≤0.03% / ≥100dB
Extras: VU meter, remote control, bass and treble with center detents, settings memory
Power: 24V/4.5A adapter included
In the box: MC331, 2 vacuum tubes, 2 tube covers, Bluetooth antenna, remote control, 24V/4.5A power adapter, user manual
Genuine Fosi Audio stock. Free shipping on every order, 45-day returns.
Fosi Audio MC331 vs similar options
vs Fosi Audio MC351: Adds dual TPA3255 chips rated 165W × 2 + 350W @ 4Ω and passive subwoofer posts; pick the MC331 for 5654W tubes, a VU meter and a 3.5mm headphone output.
vs Fosi Audio BT20A Pro: Adds a TPA3255 amp rated up to 300W × 2 @ 4Ω with swappable op-amps; pick the MC331 for USB, optical and coaxial inputs, tubes, a VU meter and a remote.
Yes. Every unit we sell is genuine and brand-new, shipped in its original packaging, and backed by our 1-year TonePier warranty and 45-day returns.
Where does my order ship from, and how long does it take?
Every order ships from our warehouse in China, with full tracking, and most orders ship within 3 business days. Shipping is free on every order; most US orders arrive within 7–15 business days and most orders to other countries within 7–20 business days — see our shipping policy for details.
What if it isn't for me?
You get 45 days to decide. Keep the packaging, keep it in like-new condition, and send it back for a refund. Ear tips unsealed for hygiene reasons are fine — we expect you to actually listen.
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