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Q: Why does my power indicator not light up?

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

2. Please check that the AC power outlet is supplying power, make sure the power LED on the power supply will stay on.

3. Please replace another power supply and try it again.12-24V DC power supply are suitable.

4. If you make sure the power supply is defective, please contact us for exchange.


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

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

2. Please remove all the inputs then check whether cracking noise disappears or not, the cracking may be from the audio source or input cables.

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


Q: Why Bluetooth is intermittent?

1. Please try with another Bluetooth device.

2. Make sure there is no interference from other electronic devices between the Fosi Audio Product and the audio source.

3. Place your device close to the Fosi Audio Product.

4. Plug in the power adapter again.


Q: My Bluetooth device cannot pair with Fosi Audio Product?

1. Make sure that you have selected the input mode switch to BT on the back panel of the Fosi Audio Product.

2. Make sure that Fosi Audio Product is powered on.

3. Make sure that Fosi Audio Product is not paired with other devices.

4. Make sure that the distance between your device and Fosi Audio Product is not too long.

5. Make sure there are no barriers between your device and Fosi Audio Product, barriers will affect the Bluetooth operation distance.

6. Please reconnect the power supply to the Fosi Audio Product, and move the Fosi Audio Product to another room to have a try.

7. Restart the Fosi Audio Product and then try to connect again, try to use another Bluetooth device.


Q: Sound quality is not good?

1. Make sure all the cables are fully connected.

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

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

4. Please check if the vacuum tube is broken or completely plugged in.


Q: Why there is no voice from my amplifier?

1. Please check whether the cable of the power supply is connected to Fosi Audio Product and whether the power indicator is on.

2. Make sure the Fosi Audio Product's indicator light is on when the power is turned on.

3. Please check that the Fosi Audio Product and your source components are turned on and not set to minimum volume, if possible replace your source and test again.

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

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

6. Please make sure the Bluetooth is paired or not, if Bluetooth is connected, AUX input will be disconnected. If you want to connect this amplifier with a 3.5mm AUX cable, you need to disconnect the Bluetooth first.

7. Please make sure that the headset is connected or not. If the headset is connected, the speaker will be disconnected.


Q: How much power does it take in standby mode? Can this amp be left on all the time?

1. 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.


Q: One channel does not work?

1. Please test whether the Bluetooth and RCA input have the same problem first.

2. If the two modes have the same problem, swap the speaker cables of the left and right channels, or change another speaker, and then test whether this channel still does not work.

3. If only RCA or Bluetooth mode does not work, change the audio source, change the RCA cable and test again, and make sure that all the cables are completely pushed into the device.


Q: Not Dolby/DTS audio and I still get noise through the USB input?

1. Please try to connect the USB Type-C/PC-USB cable to the other USB ports on your PC. Some USB ports may have unstable data transmission so please try to swap it;

2. Please try again on another computer;

3. Please replace the USB Type-C/PC-USB cable and retest;

4. Please change to use another power adapter and retest. Some aged power adapters may result in white noise.


Q: Why does my device stop working after a short time of use?

1. Make sure your audio source and the headphones, amplifier, or active speakers you connect are working well.

2. And please check over all the connections of the input and output cables.

3. Then you can try to change the audio input source, output devices, and cables to test again.

4. Also please check if the power supply works or not.


Q: 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 touching the amplifier casing, as this may cause a short circuit fault.Bare wire connection illustration

Method 2: Banana plugs connection illustration

1) Release the banana jacket;

2) Loosen the screw;

3) Insertion speaker wire and tighten the screw;

4) Tighten the banana jacket;

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 cause a short circuit. Banana plugs connection illustration


Q: How about warranty, shipping, and return policy?

1. All Fosi Audio products have 18-month warranty, click for details 18-Month Warranty.

2. Worldwide Shipping, click for details Worldwide Shipping.

3. 14 Days Free Return, click for details 14 Days Free Return.


For other specific product questions, you can directly download the user manual to view or send us an email.

Pre-sales consultation please email to shopify@fosiaudio.com

After-sales technical support please email to support@fosiaudio.com

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