Item specifics
Description
MH-M18/M28/M38 Series Bluetooth Module Product Overview
The MH-M18/M28/M38 Series Bluetooth Module is a low-power Bluetooth audio receiver module supporting Bluetooth 4.2 transmission and dual-channel stereo lossless playback. The series offers three versions – M18 (Basic/SMD version), M28 (Headphone jack output), and M38 (Built-in 5W+5W amplifier) – optimized for different application scenarios and functional requirements. The MH-M18/M28/M38 Series Bluetooth Module supports decoding of multiple lossless audio formats including WAV/WMA/FLAC/APE/MP3, with a Bluetooth range of up to 20 meters in open environments. It supports both 5V Micro USB and 3.7V-4.2V lithium battery power supply. Widely used in old speaker Bluetooth conversion, car audio system upgrades, DIY speaker building, and more.
MH-M18/M28/M38 Series Bluetooth Module Key Features
Bluetooth 4.2 Version: The MH-M18/M28/M38 Series Bluetooth Module supports Bluetooth V4.2 with auto-connect technology, compatible with HFPV1.7, A2DPV1.2, AVRCPV1.5, AVCTPV1.2, AVDTPV1.2 protocols.
Lossless Audio Decoding: The MH-M18/M28/M38 Series Bluetooth Module supports WAV/WMA/FLAC/APE/MP3 lossless decoding with stereo dual-channel output.
Three Models Available: The MH-M18/M28/M38 Series Bluetooth Module provides M18 (Basic/SMD version), M28 (Headphone jack output), and M38 (Built-in 5W+5W amplifier).
Flexible Power Supply: The MH-M18/M28/M38 Series Bluetooth Module supports 5V Micro USB power and 3.7V-4.2V lithium battery power.
Ultra-Low Power Consumption: The MH-M18/M28/M38 Series Bluetooth Module has broadcast standby of 5.5mA, operating 20mA, deep sleep only 3μA.
Wide Temperature Range: The MH-M18/M28/M38 Series Bluetooth Module operates from -40℃ to +85℃.
High Sensitivity: The MH-M18/M28/M38 Series Bluetooth Module achieves receiver sensitivity up to -87dBm.
Transmission Distance: The MH-M18/M28/M38 Series Bluetooth Module delivers up to 20 meters in open environments.
MH-M18/M28/M38 Series Bluetooth Module Applications
The MH-M18/M28/M38 Series Bluetooth Module is widely used for upgrading old speakers to Bluetooth; automotive audio systems for phone music playback; DIY speaker building; Bluetooth headphone/amplifier modifications; multimedia speakers; smart home audio devices; and various other Bluetooth audio reception applications.
MH-M18/M28/M38 Series Bluetooth Module Key Advantages
Three Models for Flexible Selection: The MH-M18/M28/M38 Series Bluetooth Module provides M18 for cost-conscious DIY enthusiasts, M28 for headphone-output scenarios, and M38 with built-in dual 5W amplifier for direct speaker driving – truly plug-and-play. Lossless Audio Decoding: The MH-M18/M28/M38 Series Bluetooth Module supports mainstream lossless formats like FLAC/APE/WAV with stereo dual-channel output, delivering wired-quality sound. Ultra-Low Power Design: The MH-M18/M28/M38 Series Bluetooth Module features deep sleep of only 3μA, operating current just 20mA – ideal for battery-powered portable devices. Wide Voltage Power Supply: The MH-M18/M28/M38 Series Bluetooth Module supports 3.7V-5V input, compatible with both lithium batteries and Micro USB for versatile scenarios. 20-Meter Long-Range Transmission: The MH-M18/M28/M38 Series Bluetooth Module delivers up to 20 meters in open environments. Industrial-Grade Wide Temperature: The MH-M18/M28/M38 Series Bluetooth Module operates from -40℃ to +85℃. M38 Built-in 5W+5W Amplifier: The M38 model of the MH-M18/M28/M38 Series Bluetooth Module can directly drive two 2-8Ω, 3-5W speakers (4Ω5W recommended) without external amplifier. M38 USB Sound Card Support: The M38 model of the MH-M18/M28/M38 Series Bluetooth Module offers plug-and-play USB sound card, connecting to computer via USB cable for direct audio output.
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FAQ
1. What are the MH-M18 / M28 / M38 Bluetooth Audio Receiver Modules?
They are low-power Bluetooth 4.2 audio receiver modules that are part of the MH-M18/M28/M38 Series Bluetooth Module, supporting stereo lossless playback. Bluetooth connection range reaches up to 20 meters in open environments. They are widely used in Bluetooth audio reception and speaker DIY modifications.
2. What are the main differences between M18, M28, and M38 within the MH-M18/M28/M38 Series Bluetooth Module?
Key differences in the MH-M18/M28/M38 Series Bluetooth Module are as follows:
| Feature | M18 | M28 | M38 |
|---|---|---|---|
| Micro USB Power | × | √ | √ |
| 3.5mm Headphone Jack | × | √ | × |
| Built-in Amplifier | × | × | √（5W+5W） |
| Lithium Battery Power | √ | √ | √ |
| USB Sound Card (Driver-Free) | × | × | √ |
| Volume Memory/Adjustment | √ | × | × |
| MUTE Interface | √ | × | × |
| Button Expansion | √ | × | × |
3. What Bluetooth protocols and audio formats does the MH-M18/M28/M38 Series Bluetooth Module support?
The MH-M18/M28/M38 Series Bluetooth Module supports Bluetooth V4.2 with protocols including HFP V1.7, A2DP V1.2, and AVRCP V1.5. Audio formats supported include WAV/WMA/FLAC/APE/MP3 lossless decoding with stereo output.
4. How do I interpret the LED indicator status on the MH-M18/M28/M38 Series Bluetooth Module?
After power-on, the blue LED on the MH-M18/M28/M38 Series Bluetooth Module indicates: fast flashing when not connected, steady on when Bluetooth is connected, and slow flashing during audio playback.
5. What power supply options does the MH-M18/M28/M38 Series Bluetooth Module offer?
5V power: Via Micro USB or 5V/GND pins
Lithium battery (3.7V-4.2V) : Via VBAT/GND pins
For M18, when using a 3.7V lithium battery, the onboard diode must be replaced with a 0Ω resistor or the pads shorted.
6. What is the power consumption of the MH-M18/M28/M38 Series Bluetooth Module?
The MH-M18/M28/M38 Series Bluetooth Module consumes approximately 5.5mA in unconnected broadcast state, 20mA in connected working state, and 3µA in deep sleep mode.
7. What are the audio output requirements for the M38 model of the MH-M18/M28/M38 Series Bluetooth Module?
The M38 model of the MH-M18/M28/M38 Series Bluetooth Module has a built-in 5W+5W dual-channel amplifier and can directly drive two 2-8Ω, 3-5W speakers. Note: The two amplifier outputs cannot be connected in parallel, and the two negative poles cannot be connected together, otherwise the amplifier chip will be damaged. The M38 already has a built-in amplifier and must not be connected to an external amplifier.
8. What is the audio output method for the M28 model of the MH-M18/M28/M38 Series Bluetooth Module?
The M28 model features a 3.5mm headphone jack for direct headphone connection, and can also output via L/R/AGND pins for connection to an amplifier board's audio input.
9. What expansion features does the M18 model of the MH-M18/M28/M38 Series Bluetooth Module support?
The M18 supports button expansion (requiring external resistors and buttons for volume control/track switching), MUTE interface (outputs high 3.3V when muted, low 0V when playing), and volume memory function (volume >15% is retained after power-off; <15% resets to 15%).
10. What are the precautions when using these modules?
Signal interference: The Bluetooth antenna of the MH-M18/M28/M38 Series Bluetooth Module is susceptible to high-frequency or strong electromagnetic interference — keep away from wireless transmitting devices and avoid placing the board near metal objects
Hum/noise issues: If connecting to an amplifier produces hum, solder the module's output wires directly (avoid using plug-in connectors), keep ground wires short and thick; connect audio ground to the amplifier's audio input ground
ESD protection: As these are bare-board designs, avoid touching components with bare hands to prevent ESD damage
Lithium battery safety: The charging interface is current-limited and does not include charge management — always use genuine batteries with protection circuits
Power quality: Bluetooth audio modules like the MH-M18/M28/M38 Series Bluetooth Module are sensitive to power quality — an LC filter circuit is recommended, especially when using switching power supplies