The Fosi Audio BT20A Pro is a compact Bluetooth power amplifier built on the TPA3255 Class D chip, rated at up to 300W × 2 into 4Ω, with Bluetooth 5.0 and RCA inputs, a pre-out, and bass and treble controls. It suits desktop and bookshelf systems running passive speakers from a phone or a wired source.
Who the Fosi Audio BT20A Pro is for
Desktop and bookshelf speakers: The 5 × 5 × 1-inch chassis drives passive speakers rated from 2 to 8Ω in setups where a full-size integrated amp makes no sense.
Phone-first listening: Bluetooth 5.0 with SBC and AAC lets a phone play straight to it, while the RCA input takes a wired source such as a DAC or CD player.
Bright speakers or a reflective desk: Bass and treble controls let you rebalance the sound at the amp instead of adding EQ software to the chain.
Adding a subwoofer: The pre-out can feed an active subwoofer alongside your passive speakers, one of the setups Fosi suggests.
Op-amp rollers: Its two NE5532 op-amps plug into sockets, and Fosi lists the LME49720HA, MUSES02 and OPA2134PA as replacements.
Skip it if: you need a USB, optical or coaxial input for a computer or TV; the BT20A Pro takes Bluetooth and RCA only.
Fosi Audio BT20A Pro key specs
Amplifier chip: TPA3255 (Class D)
Output power: Up to 300W × 2 @ 4Ω (Fosi max rating)
Speaker impedance: 2–8Ω
Inputs: Bluetooth 5.0 (SBC, AAC), RCA
Outputs: Passive speaker terminals, pre-out
Tone controls: Bass and treble
Op-amps: 2 × NE5532, socketed (swappable)
SNR: ≥108dB
Power input: 24–48V DC
Dimensions: 5 × 5 × 1 in
Genuine stock, 1-year warranty. Free shipping on every order, 45-day returns.
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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