If you want one box with Bluetooth, a remote and a subwoofer output, the Fosi BT20A Max is the best Class D amplifier on this list; if you already own a DAC or streamer, the Fosi ZA3 is the cheaper way to a balanced input. Watt ratings on these spec sheets use different distortion limits and supply voltages, so read the buying section before you pick the biggest number.
At a glance
- Best for: 85 to 92 dB bookshelf speakers. The base versions of the five amps were listed from $109.99 to $249.99 at the makers’ stores on October 31, 2026.
- Standout: The BT20A Max lists Bluetooth 6.0 with LDAC, a motorized volume knob with remote and a subwoofer output. The ZA3 lists a balanced XLR/TRS input and a stereo/mono mode.
- Watch out for: The BT20A Max has no USB, optical or coax input. One independent test found the ZA3 short of its 4 Ω rating. The AIYIMA A80 has no tube stage.
- Compared to: The WiiM Amp adds Wi-Fi streaming at a higher listed price. Fosi’s original BT20A costs less and lists 100 W × 2 maximum.
- Bottom line: BT20A Max for an all-in-one, ZA3 for the lowest price, an A20 MONO pair if you own a preamp, A80 or D03 for a built-in USB DAC.
On October 31, 2026 we read the five maker pages (linked below), TI’s TPA3255 and TPA3116D2 pages, and three reviews: Erin’s Audio Corner on the ZA3 (March 2024), Soundphile on the BT20A Max (May 2026) and Pragmatic Audio on the A20 MONO (August 2026). Owner comments come from summaries already on our product pages.
We did not test or measure these amps and make no sound-quality claims. The A20 MONO page shows specs only as images, so its figures come from a retailer listing and the Pragmatic review. We found no independent bench data for the BT20A Max, A80, D03 or A20 MONO.
Specs of the five budget Class D amps
| Amp | Chip | Output as published | Load | Inputs | Wireless and DAC | Sub out | Maker store price, Oct 31, 2026 |
|---|---|---|---|---|---|---|---|
| Fosi BT20A Max | TPA3255, PFFB | 300 W × 2 max, 180 W × 2 RMS at 4 Ω | 2 to 8 Ω | 2 × RCA, Bluetooth | Bluetooth 6.0, LDAC, aptX Lossless | Yes | $249.99 ($279.99 with GaN supply) |
| Fosi ZA3 | TPA3255 | Stereo 155 W or 180 W × 2 at 4 Ω; mono 235 W | 2 to 8 Ω | RCA, XLR/TRS | None | Yes | $109.99 to $149.99, by supply |
| AIYIMA A20 MONO (one block) | TPA3255, PFFB | 300 W at 4 Ω (10% THD+N), 200 W (1%)* | 2 to 8 Ω* | RCA, XLR/TRS | None | Yes* | $149.99 with supply, $129.99 without |
| AIYIMA A80 | TPA3255, ES9038Q2M DAC | 300 W × 2 at 4 Ω | 4 to 8 Ω | RCA, TRS, USB, optical, coax, Bluetooth | Bluetooth 5.1 (aptX HD); USB 384 kHz/32-bit, DSD256 | Aux out | $229.99 ($199.99 without supply) |
| AIYIMA D03 | TAS5548, TAS5624 | 150 W × 2 at 4 Ω, 36 V, 6% THD+N | 4 to 8 Ω | RCA, USB, optical, coax, Bluetooth | Bluetooth 5.0 (aptX HD); digital up to 24-bit/192 kHz | Yes | $160.00 |
Sources: Fosi BT20A Max, Fosi ZA3, AIYIMA A80, AIYIMA D03 and AIYIMA A20 MONO pages. *The A20 MONO page lists no text specs; these figures come from the Audiophonics listing and the Pragmatic Audio review. Power figures are the makers’ claims, not measurements.
About the old $250 cap: a pair of A20 MONO blocks is $299.98 with supplies and the BT20A Max is $279.99 with the GaN supply, so this page no longer promises a price ceiling.
How to choose a Class D amp
Chip class: TPA3255 or TPA3116
Most amps at this price use one of two Texas Instruments chips. TI rates the TPA3116D2 at 2 × 50 W into 4 Ω at 21 V, with a 26 V supply limit. The TPA3255 accepts 18 to 53.5 V, is rated at 2 × 315 W into 4 Ω at 10% THD+N, and can run bridged as a mono amp. Fosi’s original BT20A uses a TPA3116 and lists 100 W × 2 maximum; its Pro and Max use a TPA3255 and list 300 W × 2. The chip sets the ceiling; the output stage, supply and feedback design decide what the finished amp does.
Watt ratings and supply voltage
Wattage depends on the distortion the maker allows and on the supply. TI’s page for the TPA3255 lists 315 W stereo into 4 Ω at 10% THD+N and 260 W at 1%. The A20 MONO listings give 300 W under 10% THD+N and 200 W under 1%, the D03 lists 150 W × 2 at 6% THD+N on 36 V, and the ZA3 page quotes 155 W, 180 W and 300 W in different places. Prefer 1% or RMS figures. Fosi sells the ZA3 with a 32 V/5 A or 48 V/5 A supply, $20 apart, and the BT20A Max accepts 32 to 48 V, so check what a rating assumes before buying a version without a supply.
Inputs, Bluetooth and DAC
The ZA3 and A20 MONO take balanced signals through an XLR/TRS jack. Fosi says the ZA3’s balanced input reduces interference and noise floor, which matters only if your DAC or preamp has balanced outputs. The BT20A Max has Bluetooth 6.0 (Qualcomm QCC3095) with LDAC, aptX Lossless, aptX HD, aptX Adaptive, AAC and SBC, and no input besides two RCA jacks. The A80 and D03 add USB, optical and coax inputs, with Bluetooth up to aptX HD. The ZA3 and A20 MONO have no DAC or wireless. A Bluetooth codec only works if your phone supports it too.
Speaker sensitivity and impedance
Each 3 dB of sensitivity is worth a doubling of power, according to this speaker sensitivity guide, so an 86 dB speaker needs four times the power of a 92 dB speaker for the same level. A 4 Ω speaker draws twice the power of an 8 Ω one at the same voltage, so look for an amp that rates its 4 Ω output. The ZA3, BT20A Max and A20 MONO list 2 to 8 Ω; the A80 and D03 list 4 to 8 Ω.
The five picks in detail
1. Fosi BT20A Max: the all-in-one stereo amp
Fosi lists 300 W × 2 maximum and 180 W × 2 RMS at 4 Ω, PFFB (post-filter feedback), SNR of 112 dB or better, THD+N of 0.003% or lower, a motorized volume knob with remote and a subwoofer output. Its store listed it at $249.99 on October 31, 2026. Soundphile gave it 8.5/10 in May 2026 (the reviewer received the unit from Fosi), describing the sound with the EQ off as neutral and close to other TPA3255 amps, with slightly loose bass and fuzzy fine treble, and noting an always-on fan audible from under 3 ft (1 m). See the Fosi BT20A Max details and buy links.
2. Fosi ZA3: the low-priced balanced input
The ZA3 is a TPA3255 amp with XLR/TRS and RCA inputs, stereo and mono modes and a subwoofer output. Fosi lists SNR of 106 dB or better and SINAD of 89 dB. Erin’s Audio Corner found 4 Ω stereo output well short of the rating with both channels driven, saw the amp enter protection into two 4 Ω loads, and noted that the speaker outputs stay full range when a sub is connected. His own speakers did not trip protection in normal use. There is no DAC or Bluetooth. See the Fosi ZA3 product page.
3. AIYIMA A20 MONO: a dual-mono pair for a preamp owner
One block drives one speaker, so stereo needs two. The AIYIMA store listed one block at $149.99 with a 48 V/5 A supply (the US variant showed out of stock) and $129.99 without, so a pair is about $259.98 to $299.98. Listings give TPA3255 with PFFB, SNR of 118 dB or better and THD+N of 0.002%. Pragmatic Audio gave it five stars in every category; its measurement section uses AIYIMA’s own figures (93.3 dB SINAD), not independent data. There is no DAC, remote or volume control, so you need a preamp or streamer. See the AIYIMA A20 MONO page and our A20 MONO vs ZA3 comparison.
4. AIYIMA A80: a budget integrated amp with a USB DAC
The A80 pairs an ES9038Q2M DAC with a TPA3255 and lists PFFB, 300 W × 2 at 4 Ω, THD of 0.006%, SNR of 109 dB or better, ±10 dB tone controls and a 12 V trigger. The store price was $229.99 with a US supply and $199.99 without. The AIYIMA page lists no tube stage; its only tube mention is a tube preamplifier among supported source devices. See the AIYIMA A80 page.
5. AIYIMA D03: the older USB-and-Bluetooth amp
The D03 has been on AIYIMA’s store since August 2021, and its chipset list names TI TAS5548 and TAS5624 (no TPA3255 is listed). AIYIMA lists SNR of 93 dB, THD of 0.001% at 1 kHz and 1 W, 150 W × 2 at 4 Ω on 36 V at 6% THD+N, and a remote. It was $160.00 with a 32 V/5 A supply. Its SNR figure is below the 106 to 118 dB listed for the TPA3255 picks. See the AIYIMA D03 page.
Best amp for bookshelf speakers: pairing notes
| Speaker we sell | Sensitivity | Load | Power guidance | Amps that fit |
|---|---|---|---|---|
| Klipsch RP-500M II | 92 dB at 2.83 V/1 m | 8 Ω compatible | 75 W continuous, 300 W peak | All five |
| Polk Signature Elite ES20 | 86 dB at 2.83 V/1 m | 4 and 8 Ω outputs | 20 to 125 W recommended | BT20A Max, ZA3, A80, D03 |
| Fosi SP601 | 86 dB | 4 Ω nominal | 80 W RMS, 160 W peak | ZA3, BT20A Max, A20 MONO pair |
| HiVi-Swans D3.1 MKII | About 85 dB | 8 Ω | 10 to 120 W | Same as the ES20 |
Sources: Klipsch spec sheet, Polk, Fosi and HiVi’s page for the original D3.1. We found no spec table for the MKII, so its row uses the original D3.1 figures.
The Polk and the SP601 are 6 dB less sensitive than the Klipsch, so they need about four times the power for the same level; sensitivity says nothing about sound. The SP601 is the harder 4 Ω load, so pair it with an amp that rates its 4 Ω output and keep the volume moderate.
When another pick is the better choice
| Pick | Choose it when | Choose something else when |
|---|---|---|
| Fosi BT20A Max | You want Bluetooth, a remote and a sub out in one box. | You need a wired digital input (A80, D03) or the lowest price (ZA3). |
| Fosi ZA3 | You have a DAC and want the lowest price, a balanced input and a mono option. | You want Bluetooth or a built-in DAC (BT20A Max, A80, D03). |
| AIYIMA A20 MONO pair | You own a preamp or streamer with volume control and want dual mono and XLR input. | You want one box, a remote or a total under about $260. |
| AIYIMA A80 | You want USB, optical, coax and Bluetooth in one amp at $229.99. | You want LDAC or a motorized volume knob (BT20A Max). |
| AIYIMA D03 | You want the cheapest of the five with a built-in USB DAC, Bluetooth and a sub out. | You want TPA3255 headroom or a lower noise figure (ZA3, BT20A Max, A80). |
| WiiM Amp | You want Wi-Fi streaming (AirPlay 2 receiving, Google Cast, Roon Ready) and stereo HDMI ARC. TPA3255, rated 60 W per channel at 8 Ω and 120 W at 4 Ω. | You want more rated power per dollar or a balanced input (ZA3, A20 MONO). WiiM’s overview page shows a price near $299, undated. |
WiiM sources: technical specification and overview page. For the streaming side see our WiiM Amp vs WiiM Amp Pro comparison.
What owners say
Owner feedback summarized from retailer reviews on our product pages, for the ZA3 and BT20A Max only.
- ZA3 owners cite the stereo/mono switch and the balanced input as reasons to buy. Complaints: no DAC or streaming, no tone controls, and two units needed for dual mono.
- BT20A Max owners praise the Bluetooth codec support and the subwoofer output. Complaints: no balanced input or Wi-Fi streaming, and a separate DAC needed for a better wired source.
Disclosure: links marked as sponsored are affiliate links, and we may earn a commission if you buy through them, at no extra cost to you. Prices are set by the retailers and change; the store prices on this page were read on October 31, 2026.
Frequently asked questions
What is the best Class D amplifier for bookshelf speakers on a budget?
Is a Class D amplifier good enough for hi-fi?
Should I buy a TPA3255 or a TPA3116 amplifier?
How many watts do I need for bookshelf speakers?
Do I need a separate DAC with these amps?
Which of these amps has Bluetooth?
Should I buy one AIYIMA A20 MONO or two?
Is the AIYIMA A80 a tube amplifier?
What is the difference between the Fosi BT20A, BT20A Pro and BT20A Max?
Can these amplifiers drive 4 ohm speakers?
Update log
- October 31, 2026: rebuilt around published specs and third-party reviews. Corrected the BT20A Max (Bluetooth 6.0, two RCA inputs, no USB-C, optical or coax), the A80 (no tube stage), the ZA3 and A20 MONO specs and prices. Removed testing claims and the title price cap.
Related reading
- All amplifiers in our catalog, including models not covered here
- DACs to pair with the ZA3 or A20 MONO and bookshelf speakers we sell
- A WiiM Amp and Sony SS-CS5 system and the HiVi-Swans D3.1 MKII review
