User Manual: ZK-MT21S & ZK-TB21S 2.1-Channel Bluetooth Audio Amplifier Board Module

1. Introduction

This manual provides detailed instructions for the diymore ZK-MT21S and ZK-TB21S 2.1-channel Bluetooth audio amplifier board modules. These modules are designed to provide high-quality audio amplification for left, right, and subwoofer channels, featuring Bluetooth connectivity, AUX input, U disk, and USB sound card support. Both models offer bass, midrange, and treble regulation for a comprehensive audio experience.

2. Product Features

• 2.1 Channel Audio Output: Dedicated channels for left, right, and subwoofer speakers.
• Multiple Audio Inputs: Supports Bluetooth 5.1, AUX, U disk, and USB sound card.
• Comprehensive Tone Control: Adjustable bass, midrange, and treble for full frequency coverage.
• High-End Rotary Encoder: Provides convenient and fast control for mode switching, play/pause, and song selection.
• Mechanical Power Switch: Simple turn-on/off via the main volume knob, no long press required. Automatically enters low power consumption mode when off.
• Intelligent Noise Elimination: AUX input features intelligent noise processing to reduce interference.
• USB Flash Disk Functionality: Play music directly from a USB flash disk with app support for song selection and display.
• Protection Mechanisms: Includes input anti-reverse connection, overheating, overcurrent, and short circuit protection.
• Wuzhi Audio APP Support: Offers advanced features such as custom sound effects (10-segment equalizer), BT name/password modification, prompt tone adjustment, sleep music with natural sounds, and timed shutdown.

3. Specifications

3.1. ZK-MT21S

3.2. ZK-TB21S

4. Package Contents

The package typically includes:

• 1 x 2.1 Channel Bluetooth Audio Power Amplifier Board Module (ZK-MT21S or ZK-TB21S)
• 1 x Screwdriver
• 1 x Power Connector
• Necessary screws and copper pillars for assembly (if applicable for the model)

5. Setup

5.1. Assembly (if required)

Some models may require self-assembly of the protective shell. Follow the diagram below to assemble the upper cover board, PCB, lower cover board, and secure with screws and copper pillars. Attach the knobs to the potentiometers.

5.2. Power Connection

Connect a DC 12-24V power supply with a current of ≥8A to the power input (5.5x2.1DC plug) terminal. Ensure the power supply is stable and provides sufficient current for optimal output power.

5.3. Speaker Connection

Connect your left, right, and subwoofer speakers to the corresponding terminals on the amplifier board. Ensure the speaker impedance and wattage match the specifications (L&R: 20-50W, 4-8Ω; Subwoofer: 20-100W, 3-8Ω or 4-8Ω depending on model).

5.4. Audio Input

Choose your desired audio input method:

• Bluetooth: Pair your device with the amplifier (see Operating Instructions).
• AUX: Connect an audio source via the AUX input jack.
• U Disk/USB Sound Card: Insert a USB flash disk or connect a device as a USB sound card to the USB input.

5.5. External Antenna (Optional)

If using an external antenna for improved Bluetooth range, you will need to purchase the antenna and its base separately. Refer to the welding examples for proper connection.

6. Operating Instructions

6.1. Basic Controls

• Power On/Off & Total Volume: The rightmost knob (MAIN VOLUME) controls both power and overall volume. Turn it to switch the unit on or off.
• Mode Switching: Long press the leftmost encoder knob (MODE) to switch between input modes (Bluetooth, AUX, U disk, USB sound card).
• Play/Pause: Short press the leftmost encoder knob (MODE) to play or pause audio.
• Song Switching: Rotate the leftmost encoder knob (MODE) to switch between songs (when playing from U disk or Bluetooth).
• Subwoofer Volume/Bass: Use the SUBWOOFER BASS/VOL knob to adjust the subwoofer's volume and bass level.
• Midrange Adjustment: Use the R&L CHANNEL MID knob to adjust the midrange frequencies for the left and right channels.
• Treble Adjustment: Use the R&L CHANNEL TREBLE knob to adjust the treble frequencies for the left and right channels.

6.2. Bluetooth Pairing

When in Bluetooth mode, the amplifier will be discoverable. Search for the device on your smartphone or other Bluetooth-enabled audio source and pair with it. The default Bluetooth name can be changed via the Wuzhi Audio APP.

6.3. USB Flash Disk Playback

Insert a USB flash disk containing audio files into the USB IN port. Use the encoder knob to navigate and select songs. The Wuzhi Audio APP also provides a playlist function for USB playback.

7. Wuzhi Audio APP Functions

The Wuzhi Audio APP enhances the functionality of your amplifier board. Download the official Wuzhi Audio APP to access the following features:

• Change BT Name: Easily identify multiple products by customizing their Bluetooth names.
• Change BT Password: Set or modify a Bluetooth connection password to prevent unauthorized access. This function can be turned off.
• Adjust Prompt Tone Volume: Customize the volume of system prompt sounds.
• ON/OFF Prompt Tone: Enable or disable system prompt tones.
• USB Flash Disk Playlist: Open and manage playlists from a connected USB flash disk, supporting music selection and song cutting.
• Custom Sound Effects: Utilize a 10-segment equalizer to create custom sound profiles for different speakers and audio preferences.
• Sleep Music & Timed Shutdown: Access 10 kinds of natural sounds (e.g., sound bowl, stream, wave, thunderstorm, bird song) with up to 1023 sound combinations, and set a timer for automatic shutdown.

7.1. BT Name Modification Steps

1. Enter a new BT name in the APP.
2. Click the 'Set' button.
3. The system will automatically restart.
4. Cancel pairing of your mobile device with the original BT name.
5. Find the new BT name and re-pair.

7.2. BT Password Setting Steps

Method 1 (Use Default Password):

1. Turn on the BT password switch in the APP.
2. The default password is '1111'.

Method 2 (Set Custom Password):

1. Turn on the BT password switch in the APP.
2. Enter your desired password.
3. Click the 'Setting' button.
4. The system will automatically restart.
5. Cancel pairing, and you will be prompted to enter the new password when connecting again.

8. Maintenance

• Keep the amplifier board clean and free from dust. Use a soft, dry cloth for cleaning.
• Ensure proper ventilation to prevent overheating, especially during prolonged use.
• Avoid exposing the board to moisture or extreme temperatures.
• Regularly check all connections for security and proper contact.

9. Troubleshooting

• No Output Power:
  • Ensure the audio signal input is strong enough.
  • Verify that the power supply voltage and current are sufficient (DC 12-24V, ≥8A). The actual working power of the amplifier requires a robust power supply.
• Distorted Sound or Low Volume:
  • Check speaker impedance and wattage to ensure they are within the specified range for the amplifier. Mismatched speakers can lead to poor performance.
  • Adjust the volume knobs (MAIN VOLUME, SUBWOOFER, MID, TREBLE) to appropriate levels.
  • Ensure the power supply voltage is adequate; higher voltage (within limits) generally leads to greater output power.
• Noise/Interference:
  • When using AUX input, the intelligent noise elimination processing should reduce bottom noise. If noise persists, check the quality of the AUX cable and audio source.
  • Ensure all wiring is secure and properly shielded if necessary.
• Bluetooth Connection Issues:
  • Ensure the amplifier is in Bluetooth mode.
  • Check the Bluetooth name and password settings in the Wuzhi Audio APP, especially if you have modified them.
  • Try canceling pairing on your mobile device and re-pairing.
• Automatic Shutdown:
  • The amplifier has built-in protection mechanisms against overheating, overcurrent, and short circuits. If it shuts down unexpectedly, check for these conditions.
  • Ensure adequate ventilation to prevent overheating.

10. User Tips

• Optimal Performance: For the best output power, ensure your audio signal input is sufficiently strong and your power supply voltage/current meets or exceeds the recommended specifications (DC 12-24V, ≥8A). The higher the power supply voltage, the greater the output power, and the smaller the speaker impedance, the greater the output power.
• Speaker Protection: Always turn off the amplifier when the volume is set to its lowest level to prevent potential damage to your speakers and the amplifier itself.
• Antenna Purchase: If you plan to use an external antenna for enhanced Bluetooth range, remember that the antenna and its base must be purchased separately.
• TWS Functionality: This amplifier is designed for 2.1 channel output (Left, Right, Subwoofer) from a single unit. It does not explicitly support True Wireless Stereo (TWS) pairing between multiple amplifier units.

11. Warranty & Support

For detailed warranty information and technical support, please refer to the official product documentation or contact the seller directly. A user manual in PDF format is available for download, which may contain additional information:

View User Manual (PDF)