Fosi Audio BT20A is a Hi-Fi wireless stereo 2-channel amplifier that features 100W x 2 output, it is a mini power amp which is equipped with bass and treble control. 

Product Specifications
Product Overview & Control Functions
Package Contents​
Quick Steup
Comparison Section
Warranty Information
About Fosi Audio

Product Specifications

Fosi Audio BT20A is a Hi-Fi wireless stereo 2-channel amplifier that features 100W x 2 output, and Bluetooth 5.0 streaming range up to 50ft (15m), it is a mini power amp which is equipped with bass and treble control. Simple compact design but practical and powerful! Home Hi-Fi integrated amplifier designed for the customers who pursue Hi-Fi sound!

Audio Input

Bluetooth / RCA


Bluetooth Version

Bluetooth 5.0








Max Output Power

100W + 100W@4Ω


Power Supply

24V 4.5A


DC Input Range

12 - 24V


Terminating Impedance

2Ω - 8Ω


Bluetooth Transmission Distance

Up to 50 Ft


Frequency Range

20Hz - 50kHz(±2dB)



Passive speakers


Product Size

130 x 100 x 35 mm


Product Weight


Product Overview & Control Functions

Package Contents​

Fosi Audio BT20A Amplifier*1

AC Power Cord*1

24V Power Supply*1
Bluetooth Antenna*1
Instruction Manual*1

Quick Setup​

Prepare 1: BT20A, 24V power supply, passive speakers, speaker wires or banana plugs;
Prepare 2: Connect the BT20A to the passive speakers via the speaker wire or banana plugs;

Prepare 3: Connect the 24V power supply to the DC input;

Prepare 4: Toggle the power switch on the front panel upwards to turn on the BT20A amplifier.

Note: Be sure that the volume/power switch is in the OFF positionbefore connecting the power supply.
How to connect the speaker wire?

Method 1: Bare wire connection illustration
①: Release the horn terminals block terminals;

②: Insert the two ends of the speaker wire into the amplifier and speaker terminal holes;

③: Tighten the horn terminals;

Note: Please avoid the speaker wires being exposed and touchingthe amplifier casing, as this may cause a short circuit fault;

Method 2: Banana plugs connection illustration

① Release the banana jacket;

② Loosen the screw;

③ Insert the speaker cable and tighten the screw;

④ Tighten the banana plug;

⑤ Insert the banana plug into the horn terminals of the speaker and amplifier.

Note: Please take care to avoid contact between the two banana plugs and causing a short circuit fault as some of the banana plugs are metal cased.

Bluetooth for example
Prepare your Bluetooth device (take a phone as an example)

Step 1: Install the Bluetooth antenna to the BT20A.

Step 2: Turn on the Bluetooth on your phone and search“Fosi Audio BT20A”, after connecting toBT20A, the indicator light shows blue light.

Step 3: Open the audio application, play and enjoy!


RCA Input for example
Prepare: audio source (take a phone as an example), a RCA cableor a 3.5mm AUX to RCA cable (some devices will need)

Step 1: Connect your phone to BT20A via a 3.5mm to RCA cable;

Step 2: After connecting to BT20A, the indicator light shows red light;
Step 3: Open the audio application, play and enjoy!

Note: Please keep the BT20A away from other electric device. The BT20A can't use with a radio simultaneously.


1: What type of speakers work best with BT20A Amplifier? 

• Fosi Audio BT20A works great with any 2-8Ω passive speakers. 

Note: please know that the BT20A amplifier is for passive speakers, not for powered speakers and subwoofer. 


2: Why Bluetooth is intermittent?

• Use another Bluetooth device to have a try. 

• Ensure that there is no interference from other electronic equipment between the BT20A and the audio source. 

• Put your device close to the BT20A. 

• Replug the power adapter. 


3: Why does the BT20A make serious noise when used together with a radio?

• Common feature of Class D power amplifiers is that they can cause serious noise when used with a radio, so we do not recommend using the BT20A with a radio or too close to it. 


4: Can I connect a turntable to BT20A amp, why is the volume is extremely Low? 

• As for the turntables do not have a built-in preamp, you need to add an external phono preamp before connecting BT20A. 

• As for the turntables which have a built-in preamp, the switch must be set to LINE before connecting BT20A. 


5: Why does my power indicator not light up?

• Please check that the AC power cord is securely connected to thepower supply and to an AC power outlet. 

• Please check that the AC power outlet is supplying power, makesure the power LED on the power supply will stay on.

• Please replace another power supply and try it again.12-24V DCpower supply are suitable.
• lf you make sure the power supply is defective, please contact usfor exchange.


6: Why does the sound is cracking or make a lot of electric noise? 

• Please make sure all the cables completely pushed into the devices, incompletely connection will cause this cracking. 

• Please remove all the inputs then check whether cracking noise disappear or not, the cracking maybe from the audio source or input cables. 

• If you are not using the original factory standard power supply, please replace the power supply before testing. Many power supply in the market have large interference coefficient, which will cause a lot of current sound.


7: Can I use headphone with this product? 

• No, the BT20A cannot be connected to headphones and only supports passive speakers. 


8: How can I switch between Bluetooth input and RCA input? 

• You can connect this amp via Bluetooth as well as wired input. But if Bluetooth connects, playback from the RCA input is interrupted. You need to turn off the Bluetooth from your device if you use RCA input when Bluetooth pairing. 

Input priority: Bluetooth input > RCA input 


9: Why there is no voice from my amplifier? 

• Please check whether the cable of power supply is connected to BT20A and whether the power indicator is on. 

• Make sure the BT20A's indicator light is on when the power is turned on. 

• Please check that the BT20A and your source components are turned on and not set to minimum volume, if possible replace your source and test again. 

• Check that the wire connections from the audio source to each speaker in the amplifier are connected correctly. 

• Please check that the cable is not loose, damaged. Incomplete connection is one of the main reasons for no sound. 

• Please make sure the Bluetooth is paired, if Bluetooth is connected, the playback of RCA input will be interrupted. If you want to connect this amplifier with a RCA cable, you need to interrupt the Bluetooth first. 


10: My Bluetooth device cannot pair with BT20A? 

• Make sure that BT20A is powered on. 

• Make sure that BT20A is not paired with other devices. 

• Make sure that the distance between your device and BT20A is not too long, close your device to BT20A to have a try. 

• Make sure there are no obstacles between your device and BT20A, obstacles will affect the Bluetooth operation distance. 

• Please try to change another Bluetooth audio source to test. 

• Please reconnect the power supply to the BT20A, and move the BT20A to another room to have a try. • Restart the BT20A and then try to connect again, try to use another Bluetooth device. 


11: How much power does this use in standby mode? Can this amp be left on all the time? 

• This is the class D amplifier, it will cost very low power when it is in standby mode. It can be connected all the time and it is safe without power consumption. 


12: Sound quality is not good? 

• Make sure all the cables are fully connected. 

• Adjust the treble and bass control of the power amplifier to achieve the right tone. 

• Please try to change the sound source and cables to test. 


13: Should I unplug the power cord? 

• If the item will not be used for a long time, please unplug the power plug to prevent the item from being burnt due to lightning strike. 


14: Can I bridge channel 1 and channel 2 to get 200watts? 

• NO, this amplifier can't be bridged. 


15: How can I connect BT20A to TV? 

• Because the BT20A has an RCA input, it can be connected to a TV.


16: Can BT20A accept signal from a Bluetooth microphone? 

• If your Bluetooth microphone is a Bluetooth transmitter, then yes. This amplifier is the Bluetooth receiver amplifier. 


17: Why the sound cut in and cut out? 

• Try to reduce the sound of the sound source. 

• Try to change the audio source to test. 

• Reduce the volume of the treble and bass knob on the BT20A. 

• Ensure that the positive and negative poles of the speaker output do not touch together. Some relatively large banana plugs are easy to touch together and cause a short circuit. 


18: What is the difference between BT20A and BT10A? 

• Fosi Audio BT20A has 100 Watts*2 MAX power output, the Fosi Audio BT10A has 50 Watts*2 MAX power output. 


19: Can I take the BT20A to other countries? 

Yes, the wide voltage AC 110-240V for power input can be used inany country. You only need to match the power cord adapter of the corresponding country.


Any problems please leave a message to the customer support email address:

Comparison Section

Warranty and Maintenance

• All Fosi Audio products have an 18-month limited warranty on parts and labor from the date of purchase. Please contact us if you have any problems.

About Fosi Audio​

• Fosi Audio designs and builds innovative audio products with all your music in mind. Great sound, simple but elegant designs, high-quality materials, and truly useful features are what Fosi Audio is about. We sincerely hope you get as much enjoyment from our products as we’ve had to create them!


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