Fosi Audio

Product Specifications

Product Overview

The Fosi Audio BL20A is a powerful Bluetooth 5.0 HiFi stereo amplifier with AUX pre-output, suitable for passive speakers. It features Treble & Bass control and a remote control for convenience.

Front Panel Controls:

• 1: Infrared Radiation (?): Receives signals from the remote control.
• 2: AUX/U-Disk/Bluetooth Input Indicator Light: Shows the current input mode. Red indicates AUX/USB input, Blue indicates Bluetooth input.
• 3: U-Disk Input: Slot for inserting a USB flash drive.
• 4: Bass Control: Adjusts the bass frequencies.
• 5: Treble Control: Adjusts the treble frequencies.
• 6: Multi-function Knob (Power Switch/Mode Switch/Volume Control): Used for powering the device on/off, switching input modes, and adjusting volume.

Note on Multi-function Knob: Long press to power on/off; Short press to switch mode; Turn left to decrease the volume; Turn right to increase the volume.

Rear Panel Ports:

• 7: 3.5MM AUX Input: For connecting audio sources via a 3.5mm cable.
• 8: 3.5MM AUX Pre-output: For connecting to another amplifier or audio device.
• 9: Passive Speakers Output (R/L): Connects to passive speakers.
• 10: Bluetooth Antenna Interface: For attaching the Bluetooth antenna.
• 11: DC Input: Power input port (DC 12-24V).
• 12: Bluetooth Antenna: External antenna for improved Bluetooth reception.

Diagram Description: The front panel features the Fosi Audio logo, model name, input mode indicators, an IR receiver, a USB slot, Bass, Treble, and a multi-function Power/Volume knob. The rear panel includes various input/output ports and the DC power input.

Connections Diagram Description

The rear panel of the BL20A includes:

• INPUT (7): 3.5MM AUX Input
• PRE-OUT (8): 3.5MM AUX Pre-output
• SPEAKERS OUTPUT (9): Left (L) and Right (R) speaker terminals.
• ANT (10): Bluetooth Antenna connector.
• DC 12V-24V (11): Power input.

The diagram illustrates connection options:

• Active Speakers: Connect directly to the SPEAKERS OUTPUT.
• Amplifier: The BL20A can be connected to an amplifier via the PRE-OUT port, acting as a pre-amplifier.
• Passive Speakers: Connect directly to the SPEAKERS OUTPUT.

Note: You can connect 2 passive speakers only. Alternatively, you can use the PRE-OUT as a preamplifier. All outputs can be connected simultaneously.

Remote Control

The BL20A comes with an infrared remote control with a working distance of up to 15 meters (≤15 m).

Package Contents

• BL20A Bluetooth Amplifier x 1
• Bluetooth Antenna x 1
• Remote Control x 1 (Battery not included)
• Power Adapter x 1
• AC Cord x 1
• User Manual x 1

Quick Setup

1. Step 1: Install the Bluetooth antenna to the BL20A.
2. Step 2: Connect your audio output.
   • Use speaker wire to connect the speaker's output to your passive speakers.
   • Or, use a 3.5MM audio cable to connect the 3.5MM AUX pre-out of BL20A to your amplifier, then use speaker wire to connect the amplifier with your passive speakers.
   • Or, use a 3.5MM audio cable to connect the 3.5MM AUX pre-out of BL20A to your powered speakers.
3. Step 3: Connect the power adapter to the BL20A and the socket. Long press the Multi-function Knob to power on the BL20A. The input mode indicator light should stay red after power on.

   Note 1: Please ensure the LED light on the power adapter stays on.

   Note 2: Before connecting the power supply, turn down the Bass and Treble controls to 0 (fully left) to avoid hearing damage.

4. Step 4: Connect the audio source (AUX input/U-Disk input/Bluetooth input) to the BL20A.
   • AUX Input: Use a 3.5mm audio cable to connect the BL20A and your device. The input indicator light will stay on Red.
   • U-Disk Input: Insert your U-Disk into the U-Disk input interface. The input indicator light will be red and flash continuously.
   • Bluetooth Input: Short press the Multi-function Knob to switch to Bluetooth mode (the blue input mode indicator light will flash). Turn on Bluetooth on your device, select "BL20A" for pairing. The input mode indicator light will stay blue after a successful connection.

   Input priority: The latest input mode is prioritized.

   Note: Please keep the BL20A away from other electric devices. The BL20A cannot be used with a radio simultaneously.

5. Step 5: Adjust the Volume, Bass, and Treble controls to your preference, then enjoy your music!

   Note: Ensure that all cables are completely pushed into the device.

Q&A / Troubleshooting

1. Get noise when playing music?

• Bluetooth input play mode: Try using other Bluetooth devices. Weak or unstable Bluetooth signals can cause this issue. Try moving your device closer to the BL20A.
• U-Disk input play mode: Try using other U-Disks and ensure the audio format is compatible with the BL20A (supports MP3/WMA/APE/FLAC/WAV). Make sure the U-Disk capacity does not exceed 32GB and it is functioning normally.
• AUX input play mode: Try using a different audio cable.
• Try another RCA cable and ensure the audio cable is connected correctly.
• Unplug the RCA cable from the amplifier, then turn it on to test.
• Try changing the audio source or using other brand devices.
• Check if the "Treble" volume is set too high; try reducing it.
• Ensure all cables are fully inserted into the device, as incomplete connections can cause issues.
• Keep the device away from other electronic devices.

2. All cables are connected, but there is no audio output?

• Check that the input indicator light on the front panel of the BL20A and the power supply are on.
• If the input indicator light is on, check if the volume knob is at the minimum state. If so, turn up the volume.
• Ensure the BL20A is in the desired play mode.

  Note: Bluetooth input mode: Indicator light stays blue. AUX input mode: Indicator light stays red. U-Disk input mode: Indicator light is red and flashes continuously.

• Input priority: The latest input mode is prioritized.
• Ensure the U-Disk capacity does not exceed 32GB and it works normally.
• Check if the audio source is paused.
• Try changing the sound source, cables, and speakers.
• Restart the BL20A and your device, then try to connect again.

3. My Bluetooth device can't pair with the BL20A?

• Ensure the BL20A is powered on and the LED light on the power adapter is on.
• Make sure the BL20A is not already paired with another device.
• Ensure the distance between your device and the BL20A is not too long; try moving your device closer.
• Ensure there are no obstacles between your device and the BL20A, as obstacles affect Bluetooth range (maximum transmission distance without obstacles: 164ft/50m).
• Try connecting a different Bluetooth audio source to test.
• Replug the power supply, move the amplifier to another room, and test again.
• Restart the BL20A and try connecting again. Try using a different brand of mobile phone.

4. Why is Bluetooth intermittent?

• Use another Bluetooth device to test.
• Ensure there is no interference from other electronic equipment between the BL20A and the audio source.
• Place your device close to the BL20A.
• Replug the power adapter.

5. One channel does not work?

• First, test if Bluetooth, U-Disk, and AUX inputs have the same problem.
• If all three modes have the same issue, swap the speaker cables of the left and right channels, or change to another speaker, and then test if this channel still does not work.
• If only Bluetooth, U-Disk, or AUX mode does not work, change the audio source, change the audio cable, and test again. Ensure all cables are completely pushed into the device.

6. U-Disk cannot be played?

• Try playing from different U-Disk devices.
• Ensure the U-Disk capacity does not exceed 32GB and it works normally.
• Make sure the BL20A is in U-Disk play mode.

7. U-Disk play rustling?

• This might be a song format problem. WAV files can contain DTS multi-channel audio. The BL20A supports stereo but not multi-channel. You can convert DTS to stereo using software like Foobar2000 on a computer.

8. Can't power on?

• Long press the power switch button to power on/off.
• Ensure the LED light on the power adapter stays on.
• If the LED does not light up: Unplug the power adapter from the BL20A, plug the power adapter directly into the AC power source, and check if the LED lights up. If it still does not light up, the power adapter may be faulty. Please contact Fosi Audio for a replacement.
• You can use a DC12-24V power adapter from a camera or router to connect to the BL20A to test if the BL20A can be turned on.

9. Can the BL20A be used as a pre-amp?

• Yes. There is a PRE-OUT interface on the rear panel, which can be used as a preamplifier.

10. Do I have to connect all the outputs of BL20A? Can I only connect 2 speakers? Or just use it as a preamp?

• You do not need to connect all outputs. You can connect 2 passive speakers only. Alternatively, you can connect to the PRE-OUT as a preamplifier. All outputs can be connected simultaneously.

11. Sound quality is not good?

• Ensure all cables are fully connected.
• Adjust the treble and bass controls of the BL20A to achieve the desired tone.
• Try changing the sound source and cables to test.

12. Why does the sound cut in and cut out?

• Try reducing the volume of the sound source.
• Try changing the audio source to test.
• Reduce the volume of the treble and bass knobs on the BL20A.
• Ensure that the positive and negative poles of the speaker output do not touch each other. Some large banana plugs can easily touch, causing a short circuit.

13. Does the BL20A support Bluetooth aptX and Low Latency?

• No. The BL20A does not support Dolby, aptX, aptX HD, and aptX Low Latency.

14. Can this amp be left on all the time?

• Yes, it can be connected all the time and is safe without significant power consumption.

15. Can I listen to two audio inputs at the same time?

• No, only one input mode can be used at a time.

Warranty Information

All Fosi Audio products have an 18-month limited warranty on parts and labor from the date of purchase. Please contact Fosi Audio 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!

Our website: www.fosiaudio.com

Amazon store: www.amazon.com/fosiaudio

Our Youtube channel: Fosi Audio

Our Facebook page: Fosi Audio

After-sale Service and Technical Support Email: support@fosiaudio.com, fosiaudio@hotmail.com

Fosi Audio Product's User Manual