The **CT-14B-R** is a specific variant of a Micro USB Bluetooth Audio Receiver Module, commonly used for DIY wireless speakers and portable audio projects. It is a cost-effective, low-power solution that integrates Bluetooth connectivity with a dual-channel audio amplifier. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Bluetooth Version** | Bluetooth 4.2 | | **Operating Voltage** | 3.7V (Lithium Battery) or 5V (Micro USB) | | **Output Power** | Dual Channel 5W + 5W (Stereo) | | **Speaker Impedance** | 2Ω - 8Ω (4Ω recommended) | | **Transmission Range** | ~15 Meters (Open area) | | **Dimensions** | Approx. 40mm x 20mm | --- ### 2. Main Electronic Components The board is highly integrated, containing the following primary blocks: #### A. Bluetooth SoC (System on Chip) The heart of the module is usually an AC-series Bluetooth chip (like the AC6905 or similar). This chip handles: * **RF Signal Processing:** Receiving digital audio data from your phone/PC. * **DAC (Digital-to-Analog Converter):** Converting the digital signal into an analog audio waveform. #### B. Dual Audio Power Amplifiers The board typically features two small SMD (Surface Mount Device) ICs, often the **NS4150** or **PAM8403** (or equivalents). * **Class D Efficiency:** These are Class D amplifiers, which provide high power output with minimal heat generation, ideal for battery-powered devices. * **Configuration:** Bridged-Tied Load (BTL) output to drive speakers directly without needing output coupling capacitors. #### C. Power Management * **Micro USB Port:** Used for 5V power input. * **Charging Circuit:** Some versions include a basic charging protection circuit, though it is usually recommended to use a protected 18650 battery if connecting via the battery pads. * **Filter Capacitors:** Electrolytic and ceramic capacitors are used to stabilize voltage and filter out high-frequency noise from the switching amplifier. --- ### 3. Connection Pinout | Label | Description | | :--- | :--- | | **VBAT / + / -** | Connection point for 3.7V Lithium Battery. | | **L+ / L-** | Left Channel Speaker Output. | | **R+ / R-** | Right Channel Speaker Output. | | **Micro USB** | 5V Power Supply Input. | --- ### 4. Implementation Notes * **Antenna:** The PCB includes a "meander line" copper trace which acts as the Bluetooth antenna. Do not cover this area with metal shielding, as it will severely reduce range. * **Noise Issues:** If you experience "hissing" or "digital noise," it is often due to an unstable power supply. Adding a 1000uF capacitor across the power input pins can help. * **Heat Dissipation:** While Class D is efficient, if driving 2Ω speakers at high volume, ensure the module has some airflow.