Fosi Audio BT20A MAX Bluetooth 5.4 Stereo Class-D Amplifier 300W

Fosi Audio BT20A MAX Bluetooth 5.4 Stereo Class-D Amplifier 300W with Subwoofer Output

Fosi Audio BT20A MAX — Bluetooth 5.4 Class-D stereo integrated amplifier delivering up to 300W × 2 peak / 180W × 2 RMS at 4 ohm. Supports 2-8 ohm passive speakers with dedicated subwoofer line-out for effortless 2.1 system integration. Multiple inputs: Bluetooth 5.4 (aptX-HD, aptX Adaptive, SBC), USB-C DAC, optical, coaxial, RCA. TPA3255 chipset with premium op-amp signal path delivers reference-tier measurements at consumer price. Perfect single-box stereo amp for HiVi-Swans, Klipsch, Wharfedale bookshelves or small towers. Bluetooth codec suite makes wireless listening genuinely hi-res. Direct from Fosi with our promo code, or Amazon US.

$229.99

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Video Review

Fosi Audio BT20A MAX — Bluetooth 5.4 Class-D amp with 300W peak, subwoofer out, and full digital input suite

The BT20A MAX is the top-tier refresh of Fosi’s legendary BT20A stereo integrated. Class-D architecture built on the TPA3255 chipset delivers up to 300W × 2 peak (180W × 2 RMS at 4 ohm) — enough headroom for bookshelves, small towers, or a 2.1 rig with the built-in subwoofer line-out. Bluetooth 5.4 with the latest aptX Adaptive codec, USB-C DAC input, optical, coaxial, RCA — one amp for the entire desktop or living-room system.

Why buy the BT20A MAX

  • 300W × 2 peak / 180W × 2 RMS at 4 ohm — genuinely powerful stereo output, drives most bookshelves and small towers with headroom.
  • Dedicated subwoofer line-out — proper 2.1 architecture, adjustable low-pass crossover.
  • Bluetooth 5.4 with aptX Adaptive + aptX HD + SBC + AAC — cutting-edge low-latency hi-res wireless codec suite.
  • USB-C DAC input — plug directly into Windows/Mac/Linux and skip separate DAC purchase.
  • Full input suite — Bluetooth, USB-C, optical, coaxial, RCA. Single amp handles desktop + TV + turntable rig.

Who it’s for

Anyone wanting a top-tier single-box stereo integrated with modern wireless + digital inputs. Ideal for HiVi-Swans D3.1 MKII, Klipsch RP-500M II, Wharfedale Diamond, or ELAC Debut bookshelf pairs. Compare against the AIYIMA A80 (has tube preamp for warmth) or A20 MONO pair (dedicated dual-mono).

Who should skip it

Skip the BT20A MAX if you need dedicated headphone amplification or want tube preamp warmth (A80 better). Also skip if you need only stereo and no subwoofer support — the smaller Fosi ZA3 saves money.

Common questions

Does the BT20A MAX use TPA3255? Yes — same chip family as A20 MONO and Fosi V3.

What’s new vs original BT20A? Bluetooth 5.4 (was 5.0), USB-C DAC input, higher peak power, refined signal path, dedicated sub output.

Can I use it with the AIYIMA 48V 10A GaN PSU? BT20A MAX includes its own dedicated PSU tuned for the amp — no external PSU needed.

Where to buy

Fosi direct with our promo code, or Amazon US with Prime. Both buttons below.

SKU: fosi-audio-bt20a-max Category: Brand:
Editorial synthesis of publicly-available Amazon 5-star reviews, YouTube reviews from named channels (Old Guy Hifi, Fred & Sound, The Apartment Audiophile, Fosi Audio official), and r/BudgetAudiophile / Head-Fi / Audio Science Review TPA3255 threads as of 2026-08. Aggregated themes from real long-term owner reports.

What owners consistently praise

  • Old Guy Hifi's video ("This Little Amp Hits HARD") captures the recurring owner reaction: 300W is honest, PFFB is real, and the BT20A MAX punches at a class where competitors need to be twice the price to keep up.
  • Fred & Sound's coverage ("Bluetooth 6.0 + PFFB Hi-Fi Amp Tested!") introduced the current generation to a wider audience, and Amazon 5-star reviews consistently praise the same headline: modern Bluetooth codec support (LDAC, aptX Adaptive, aptX-HD, aptX, SBC, AAC) on a cheap class-D amp is genuinely uncommon.
  • Bluetooth 5.4 with LDAC works cleanly. Owners feeding the BT20A MAX from modern Android phones (Sony Xperia, Xiaomi, Samsung Galaxy) report the LDAC 990 kbps connection is stable and audibly cleaner than the SBC-only Bluetooth on older budget amps.
  • Subwoofer output on a budget class-D amp is a real value-add. Owners running a 2.1 setup with a modest sub — often crossed at 60-80 Hz — appreciate not needing a separate crossover or receiver. This is where the BT20A MAX shines versus stereo-only amps like the Fosi ZA3.
  • PFFB (Post-Filter Feedback) is not just spec — it measures cleaner. ASR-adjacent Head-Fi threads consistently report the BT20A MAX measures better than non-PFFB TPA3255 amps at moderate-to-high output levels — cleaner distortion at loud volumes.
  • Cool-running Class-D in a compact chassis. Owners install the BT20A MAX in enclosed shelves or living-room cabinets without heat concerns.
  • The Apartment Audiophile's "I Found the Catch" video — even the "critical" reviewer landed on a mild caveat rather than a real complaint, which owners cite as further evidence the BT20A MAX genuinely delivers.

Common use cases owners mention

  • Simple streaming-first 2.1 setup: phone → Bluetooth → BT20A MAX → speakers + sub. The recurring reason to buy: no computer, no streamer, no DAC in the chain. Bluetooth from the phone directly to the amp, subwoofer out to a modest sub, real 2.1 hi-fi.
  • Bookshelf-with-sub small-room setup. Owners pair the BT20A MAX with Klipsch RP-500M II, Wharfedale Diamond 12.1, HiVi-Swans D3.1 MkII, or the brand-matched Fosi SP601 Orange plus a sub.
  • Second-system rebuild for a bedroom, den, or garage. Small footprint, Bluetooth streaming, real amplification power — the whole system is just the amp + speakers + optional sub.
  • Upgrade from a soundbar to a real 2.1 setup. Amazon reviews from owners moving up from soundbars repeatedly name the BT20A MAX as the amp that made 2.1 hi-fi comparable in complexity to their soundbar (just with better sound).
  • Bluetooth-first casual listener with occasional wired sessions. Owners who primarily stream from a phone but occasionally want the wired path (for critical listening or a TV) appreciate the BT20A MAX handling both roles.

Common critical notes from long-term owners

  • No built-in DAC as pure DAC — Bluetooth handles wireless, RCA in handles wired. If you want a proper DAC in the chain, use a separate DAC (see the AIYIMA D20 or Topping E30 II) into the RCA input.
  • Not balanced. Owners planning a balanced monoblock chain should look at the AIYIMA A20 MONO pair with balanced source instead.
  • Subwoofer output is high-pass filtered fixed, not adjustable. Owners wanting per-sub crossover flexibility should use a sub with its own crossover (most subs have this).
  • Bluetooth codec negotiation requires the source to support the codec. Older iPhones will negotiate to AAC (fine) rather than LDAC (which iOS does not support). Android phones with LDAC in developer options give the best wireless result.
  • No streaming apps or WiFi — Bluetooth only for wireless. Owners wanting Roon endpoint or WiFi streaming should feed the BT20A MAX from a WiiM Ultra or Fosi Audio S3 streamer via RCA.
  • Stock brick works, upgraded PSU sounds better. Owners report an audible upgrade moving to a 48V 6A Linear PSU or 48V 10A GaN PSU.

Best pairings from real owner reports

Recommended setup workflow

  1. Pair Bluetooth with your primary phone / tablet first. Force LDAC in Android developer options if given the choice; iOS negotiates to AAC automatically (which is still fine).
  2. Wire the subwoofer if you have one. Sub-out to the sub's line-in; set the sub's own crossover to 60-80 Hz and adjust level modestly.
  3. Position speakers 8-24 inches from the back wall with modest toe-in.
  4. Feed a wired source from RCA in. Optional but useful for owners who occasionally use a computer or streamer.
  5. Start with the stock PSU. Upgrade to a linear or GaN PSU only if the noise floor bothers you — many owners never bother.
  6. Set volume from the amp; do not run source volume at 100% and amp at low. Fixed amp gain means source volume matters for the noise floor.
  7. Break in for 100+ hours before serious A/B. TPA3255 amps consistently settle in the first weeks.

Overall verdict from owner community: the Fosi Audio BT20A MAX is a community favorite streaming-first budget class-D amp with real subwoofer output — the natural pick for owners building a simple 2.1 hi-fi rig around Bluetooth streaming without a separate DAC or streamer. Skip it if you need balanced monoblock topology (look at the AIYIMA A20 MONO pair), if switchable stereo/mono matters (Fosi ZA3), or if you want the tone controls / room correction / streaming polish of a receiver (Denon AVR-X1800H or Onkyo Icon A-50). For the "phone + speakers + sub" listener, this is the community pick.

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Specification

BrandFosi Audio
ModelBT20A MAX
TypeBluetooth 5.4 Stereo Class-D Integrated Amplifier
Amplifier ChipsetTPA3255 Class-D
Peak Output300 W × 2
Rms Output180 W × 2 at 4 ohm
Speaker Impedance2 - 8 ohm
Subwoofer OutputDedicated line-level with adjustable low-pass crossover
InputsBluetooth 5.4, USB-C DAC, Optical, Coaxial, RCA
Bluetooth CodecsaptX Adaptive, aptX HD, aptX, SBC, AAC
Usb DecodingPCM up to 32-bit / 384 kHz
DimensionsApprox. 6.3 x 4.3 x 1.7 in (160 x 110 x 43 mm)
WeightApprox. 1.5 lb (680 g)
Power SupplyExternal DC 48V / 5A adapter included
CertificationsCE, FCC, RoHS
Warranty18 months manufacturer
In The BoxBT20A MAX unit, 48V power adapter, Bluetooth antenna, USB-C cable, remote, user manual

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