Fosi Audio BT20A Pro Amplifier Review – Small Yet Powerful

Fosi Audio BT20A Pro -Front View

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Current testing methodology is v1.2

Release Date
2.42 lb
5 x 5 x 1 in

I’m a huge fan of Fosi Audio, and they’ve been around long enough now to have established some decent street cred. 

The TB10D is one of my favorite small Class D amplifiers that they make, and the prices of all of their gear are really affordable.

The Fosi Audio K5 gaming headphone deck is also something that stays permanently on my desk. 

Overall, I’m a bit of a fan but I also do find and acknowledge that there are some limitations with the Class D output.

The Fosi Audio BT20A Pro is an upgrade from the BT20A and it comes with a kicking 300-watt per channel output capacity running into 4 ohms. 

Editor’s Pick

Fosi Audio BT20A Pro

A Class D amplifier that certainly packs a big punch.

Price Range: $
Brand: Fosi Audio
Fosi Audio BT20A Pro on top of an amplifier


The Fosi Audio BT20A Pro is a bit of an upgrade and a better version of the BT20A.

If you’re familiar with the earlier unit, then the biggest standouts for the Pro version are that they’ve pretty much doubled the power output and have included a pre-out jack point.

There are some other tasty elements like the ability to swap out the op-amp to change the overall sound signature and signal processing if that appeals to you.

It has a ​​300-watt per channel output capacity. So for those of us that are typically going to be running 8 ohms, you’re looking at a max power output of 150 watts per channel.

The Fosi Audio BT20A Pro offers plenty of room to drive whatever speakers you’re looking to drive.

The Specs

  • Max Power Output:  300Wx2 @4Ω
  • SNR:  ≥108dB
  • Terminating Impedance:  2-8Ω
  • THD:  0.005%
  • Power Amplifier Chip:  TPA3255
  • Power Supply:  32V 5A
  • Input Range:  DC 24V-48V
  • Frequency Response Range:  20Hz-20kHz(±1.2dB)
  • Bluetooth Transmission Range:  Up to 50Ft
  • Bluetooth Codec:  AAC/SBC

What’s in the Box?

  • Fosi Audio BT20A Pro
  • Power supply
  • AC power cord
  • User’s Manual

Stuff I like

  • Clean and powerful sound
  • Small and compact size
  • Solid build quality
  • With two input options

Stuff I like less

  • Soundstage is lacking
  • No remote control

Comparable products to consider

Fosi Audio BT30D
Fosi Audio BT30D

If you’re looking for a more affordable option that still packs a punch, the Fosi Audio BT30D is worth considering for less than $100.

Build Quality

The build quality of the BT20A Pro is typical Fosi Audio – a nice steel casing with responsive tone and volume pots with a simple on and off switch.

I find their terminals to be of really good quality, plus they’re capable of taking banana plugs or being unscrewed to take naked speaker cable directly.

The Bluetooth aerial is a Bluetooth aerial, but it does have a decent-quality feel to it.

The small rubber feet underneath create a small lift from whatever you place it on, so it’s not going to scratch anything.

It won’t pick up too much vibration and if needed, it would some heat dissipation through the bottom panel.

Fosi Audio BT20A Pro - Side View
 Equipped with a flick power switch and three aluminum knobs | Make Life Click


There are two ways to send audio to the Fosi Audio BT20A Pro. 

The first, as the BT in the name suggests, is via Bluetooth. It has a capacity of up to 50 feet but in normal operating conditions, I would say anywhere between 10 and 20 meters.

I’ve found the connection to be absolutely solid and have had no issues with dropouts while using my phone, walking around large rooms, and heading down to the other end of my house.

Of course, it has its limitations but if you stay within a respectable range of under 15 meters, it seems to have no difficulty providing solid and consistent connectivity. Well done, Fosi, on that front.

Fosi Audio BT20A Pro - Back
The ports of Fosi Audio BT20A Pro | Make Life Click

The other input option you have is with an RCA in.

Personally, I like to use Amazon Alexa to input in this kind of device as it gives me the ability to voice-control my audio.

Also, I’m not looking for a high-end pure audio file experience with a unit like this. So it’s the perfect combination.

You could run anything else that can push audio through an RCA connection.

Tone Control

There’s a bass and treble port on the Fosi Audio BT20A Pro that helps you adjust the EQ as you’d like. I didn’t find the bottom end as punchy as some of their other units, which I dialed up a little bit.

Just a small tweak made a huge difference, but if I over-dialed it, I found that it started to get a little bit wooly and a little bit flooded with the kind of bottom end I wasn’t too interested in.

Generally, I tend to run these things flat so the only adjustment I made was about a 1:00 adjustment to the base control and the resulting sound was pretty great.


It’s a nice little addition to have a pre-out on a unit this size.

Fosi Audio BT20A Pro Thickness
Size comparison to an iPhone | Make Life Click
Fosi Audio BT20A Pro Size comparison

You can either run the unit just with the two stereo speaker cables running out the back to a couple of bookshelf speakers, which I’d recommend as a great size pairing for a unit like this. 

Or you can run the pre-out to an active subwoofer, active speakers, or even another amp if that’s what you would like.

What an awesome way to be able to expand the capabilities of the unit beyond just the stereo audio player.

Form Factor

The form factor, like all Fosi Audio units, being a Class D amp is tidy.

If you’re short on space or if you like the aesthetics of a small AMP unit, then the Fosi Audio BT20A Pro is a great choice. 

I love that when I look at this next to my bookshelf speakers, it creates such a nice minimalist look, and yet that Class D amp can pack some serious punch.

Fosi Audio BT20A Pro vs. K5
Fosi Audio BT20A Pro vs. Fosi Audio K5 Pro Mini Stereo Gaming DAC

Sound Signature

I typically find Class D amps or the Fosi Audio range to be quite analytical in that it’s quite a direct audio output.

They’re not as musical as the integrated amps that I have and probably not as musical, but I think all the other features of this unit overcome any negatives I have for the unit overall.

The sound is big, strong, direct, and may not be as warm. The sound stage may not be as wide, but it definitely comes out hard and strong. 

Fosi Audio BT20A Pro 300W x2 TPA3255 Bluetooth 5.0 Home Audio Stereo 2 Channel Amplifier Receiver Mini Hi-Fi Class D Upgraded Integrated Amp for Speakers with Bass Treble Control
Fosi Audio BT20A

Final Thoughts

For anybody that’s looking at spending under $200 for a Class D amp who also wants the Bluetooth option or the pre-out option, then this is an absolute winner.

If you’ve got any questions, just fire them away in the comments below, and I’d be more than happy to get into it.

Fosi Audio BT20A Pro - Side View
Fosi Audio BT20A Pro
Sound Quality
Build Quality
Value for money

Endless hours of experimentation, professional work, and personal investment in Home Theatre, Hi-Fi, Smart Home Automation and Headphones have come to this.

Former owner of Headphones Canada, a high-end headphone specialty retailer.

This post was last updated on 2024-05-23 / Some images from Amazon Product API & some links may be affiliate links which may earn us a commission from purchases.

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