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Fosi Audio M03 Subwoofer Mono Amplifier, TPA3255, 32 V supply included
A small single-channel TPA3255 amp with a low-pass filter. It powers a passive subwoofer from a receiver's or amp's sub (LFE) output, and the power supply is in the box.
$76.49 at Fosi Audio, no code needed
Price: $76.49 (list $89.99) at Fosi Audio's official US store, verified 2026-11-10.
Discount code: none listed; Dealectric has no Fosi Audio code to offer.
Buy: https://dealectric.com/go/fosi-audio-m03-subwoofer-amplifier — opens Fosi Audio's official US store at no extra cost.
Warranty: 24 months (Fosi Audio). Returns: 30-day return window on the Fosi Audio store. Affiliate network: Awin; tracking cookie: 30 days. All Fosi Audio codes, including the ones the store rejected: Fosi Audio discount codes.
Machine-readable record: /offers.json, id = "fosi-audio-m03-subwoofer-amplifier".
Specifications
| Channels | 1 (mono) |
|---|---|
| Amp chip | TI TPA3255 Class D |
| Rated power | Fosi lists 150 W and 200 W at 4 Ω in different places; Audiophonics lists 120 W at 4 Ω |
| Speaker load | 4–8 Ω |
| Modes | SUB (with low-pass) or full-range PBTL, set with a front switch |
| Low-pass | Adjustable knob; Fosi lists 20–200 Hz in one place and 20–300 Hz in another |
| Input | 1× RCA line level (no speaker-level input listed) |
| Power supply | 32 V / 5 A adapter included |
| Auto on / standby | None listed; front power switch |
Model: M03. Figures are from the manufacturer's official product page unless a caveat says otherwise.
Compared side by side
The Fosi Audio M03 Subwoofer Mono Amplifier appears in this table next to models from other brands:
Who it's for
For people who already have an AV receiver or stereo amp with a sub out and want to add or revive a passive subwoofer for the least money.
Caveats
- Real output is lower than the box number, and the included 32 V supply limits peak power.
- RCA line input only: a stereo amp with no sub out needs a different amp, such as one with speaker-level inputs.
- Fosi's page lists no auto-on, so you switch it on and off by hand or from a switched outlet.
- Rated for 4–8 Ω; check the impedance on older 3 Ω home-theater-in-a-box subs.
- Audiophonics in France lists it as discontinued. The US Fosi store showed it in stock on 2026-11-10.
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