Fosi Audio BT20A Amplifier Review

Fosi Audio BT20A review featured

The Fosi Audio BT20A is a small form factor Class-D power amplifier. It features a Texas Instruments TPA3116D2, tone controls and oodles of power. It’s priced at $60.

Disclaimer: This sample was provided by Fosi Audio for an honest review. All observations and opinions here are my own based on my experience with the product.

Fosi Audio BT20A Amplifier Review
Add your rating here!1 Votes
Energetic, clear sound
Tone controls
Small form factor
Powerful for its size
Not as insightful as some higher-tier amps
No remote control
Our Score

Fosi Audio BT20A


In the custom of (most) small form factor budget power amplifiers, the BT20A takes the form of a black box. It’s clean and simple in design and can easily blend in with other components in your system or be tucked away in a corner.

It feels solidly built and has an anodized matte surface. Weighing in at only700g, it’s super easy to position or move around. The finish is surprisingly good for a budget amp; the BT20A has rounded edges and clean aesthetics.

Situated on the front panel is the power switch, accompanied by separate treble, bass and volume control knobs. The situation on the rear panel is similarly simple: here you’ll find an RCA input, passive speakers output, Bluetooth antenna and the DC power jack. I was pleased to discover that the power LED on the front of the unit is nice and dim so it’s not distracting.


The BT20A can receive audio via either its RCA Line in or Bluetooth. The Bluetooth receiver is limited to SBC and AAC codecs but testing with my iPhone the audio quality was more than acceptable.


How does this little budget amplifier perform? Pretty well it turns out. This tiny guy has a lot of power on tap and it can easily drive most bookshelf speakers with ease. Sure, its measurements aren’t anything to write home about but they’re perfectly acceptable for the price.

The tone controls work well and let you colour the sound to your liking. It should be noted that the treble and bass dials on my unit were turned all the way down out of the box. I’d suggest moving them both to 12 o’clock before playing any music (in the default position, the sound was muddy and muted).

Take a moment to tweak the treble and bass controls once you’ve fired up some music. I found that right in the middle on both the treble and bass works best for me but it will depend on your speakers and your individual preference.

Closeup of the front dials

The little BT20A had no trouble powering my NHT C3 speakers and had heaps of power to spare. As a result, the bass was full-bodied and tight (even with the tone set to neutral), the midrange was clear and the treble lively and detailed.

The BT20A sounds energetic and dynamic. It takes the polyrhythmic beat of The Pineapple Thief’s “Alone at Sea” and shows it has a good sense of rhythm. The details and resolution are good, the vocals are engaging and the overall performance is better than I had expected from this tiny black box.

Of course, it doesn’t sound as muscular or insightful as a higher-tier product or quite as organic as a good Class-A amplifier but I think it sounds great relative to its low price. Playing through Carbon Based Lifeforms’ “Interloper”, my speakers were filling the room with rich yet tight bass and the synthesizers were swooping around me in all directions.

BT20A RCA ports and binding posts


The Fosi Audio BT20A is ideal for anyone looking for a small and affordable speaker amplifier. As long as you’re expectations are realistic, there’s little chance of being disappointed. If you need an amp for a budget or secondary system and don’t want to spend a bundle, the BT20A is the perfect solution. At this price, you couldn’t ask for more.

  • Power Adapter: 24V/4.5A
  • DC Input Range: 12-24V
  • Terminating Impedance: 2 Ohm – 8 Ohm
  • MAX Power Output: 100W x 2
  • THD ≤ 0.04%
  • Frequency Range: 20Hz – 20kHz (±1 dB)
  • SNR ≥ 98dB
  • Input Sensitivity ≤ 280mV
  • Input Mode: Bluetooth and RCA
  • Bluetooth Transmission Distance: Up to 50 Ft
Package Includes
  • Fosi Audio BT20A Amplifier*1
  • AC Power Cord*1
  • 24V Power Supply*1
  • Bluetooth Antenna*1
  • Instruction Manual*1

Stay in the Loop with the Latest News and Updates!

We don’t spam! Read our privacy policy for more info.

Founder of Prime Audio
Notify of

Oldest Most Voted
Inline Feedbacks
View all comments
1 year ago

Would this work for hooking up to a couple of passive stage monitors? I would like to use my passive monitors to play my vocals and maybe acoustic guitar through during rehearsals. Obviously the output is far to low to be heard at the moment when I go straight from my PA into the monitors, but I’m hoping putting this in between will amplify my monitors enough for me to be heard over the band.

1 year ago
Reply to  Tyler

My passive monitors take 1/4″ cables only and this is the only amplifier I’ve found with 1/4″ L/R outputs.
If this item won’t do the trick, can you please recommend something for me?

1 year ago
Reply to  David Becker

I got the bt20a pro, but it doesn’t have 1/4″ outs. I guess this one doesn’t either…
Is there any amplifier out there that connects by 1/4″ cables?

1 year ago

Thank you for your honest review. I am looking to hook up a tv to two floor model speakers, on a tv that gets watched intermittently. This sounds like a very viable option.

1 year ago

Hi David, thank you for your review it was fantastic I was thinking of purchasing a fosi in particular this one you’ve reviewed but after the issues with the treble and bass Im a bit put off. I’ve also heard about tube amps and was looking at the fosi T20 tube amp to run my turntable they also have an audio box X2 Phono tube pre amp. I have a mid range budget and small room but play vinyl all the time have a set of bookshelf paradigms, 2 xperience pro-ject TT which are currently connected to an NR1710 Marantz receiver but I’d love to place them on a seperate stereo setup as I feel I’m missing out on alot music wise with my current set up. Would love some guidance from an experienced audio man like yourself. So grateful I came upon your website, keep up the great work.

1 year ago
Reply to  David Becker

Excellent thank you David I look forward to seeing it,

Subscribe to Our Newsletter

Stay in the Loop with the Latest News and Updates!

We don’t spam! Read our privacy policy for more info.