The Fosi Audio Bluetooth Power Amplifier Board is a series of high-power stereo audio modules designed for DIY wireless speakers and transponders. This user guide covers several models: ZK-1002, ZK-1002L, ZK-502C, ZK-502L, ZK-502T, ZK-1002T, and ZK-TB21. These boards feature 2-channel (or 2.1-channel for ZK-TB21) output with built-in amplifier modules, allowing direct connection to passive speakers. They offer filtering capabilities and support both Bluetooth and 3.5mm AUX audio input methods.
Function Description:
These amplifier boards serve as the core component for building or upgrading audio systems, providing amplification for passive speakers. They are designed to deliver HIFI stereo sound quality, with some models offering additional treble and bass control. The Bluetooth connectivity allows for wireless audio streaming from devices like PCs, laptops, and mobile phones, while the 3.5mm AUX input provides a wired connection option for various audio sources such as Blue-Ray/DVD/CD players and TVs. The boards are suitable for a range of passive speakers, typically within 4-8 Ohm impedance and specific wattage ranges depending on the model.
Important Technical Specifications (by model):
ZK-1002:
- Chip: TPA3116D2*2
- Input Mode: Bluetooth and 3.5mm AUX
- Work Voltage: DC 5V-27V (Above 2A)
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 100W x 2
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 50watt-300watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 3.3 * 2 * 0.95 inch
- Weight: 0.28lb/130g
- DC Socket: 5.5*2.1mm
ZK-1002L:
- Input Mode: Bluetooth
- Work Voltage: DC 5V-24V (Above 2A)
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 100W x 2
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 50watt-300watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 2.68 * 2.05 * 0.83 inch
- Weight: 0.26lb/120g
- DC Socket: 5.5*2.1mm
ZK-502C:
- Chip: TPA3116D2
- Input Mode: Bluetooth, AUX
- Work Voltage: DC 5V-27V (Above 2A)
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 50W x 2
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 30watt-200watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 3.2 * 1.98 * 0.72 inch
- Weight: 0.24lb/111g
- DC Socket: 5.5*2.1mm
ZK-502L:
- Input Mode: Bluetooth
- Work Voltage: DC 5V-24V (Above 2A)
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 50W x 2
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 30watt-200watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 2.17 * 1.5 * 0.67 inch
- Weight: 0.11lb / 52g
- DC Socket: 5.5*2.1mm
ZK-502T:
- Chip: TPA3116D2
- Input Mode: Bluetooth, AUX
- Work Voltage: DC 5V-24V (Above 2A)
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 50W x 2
- Treble and Bass Control: Yes
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 15watt-100watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 3.72.760.83 inch
- Weight: 0.34lb/154g
- DC Socket: 5.5*2.1mm
ZK-1002T:
- Chip: TPA3116D2
- Input Mode: Bluetooth, AUX
- Work Voltage: DC 5V-24V
- Channel: 2 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 100W x 2
- Treble and Bass Control: Yes
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 50watt-300watt
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 2.763.700.83 inch
- Weight: 0.37lb/170g
- DC Socket: 5.5*2.1mm
ZK-TB21:
- Chip: TPA3116D2
- Input Mode: Bluetooth, AUX
- Work Voltage: DC 12V-24V
- Channel: 2.1 CH Stereo Output
- Bluetooth Version: Bluetooth 5.0
- Bluetooth Transmission Distance: 50 Ft
- MAX Power Output: 50W*2 (R&L) +100W (Subwoofer)
- Treble and Bass Control: Yes
- Terminating Impedance: 4 Ohm-8 Ohm
- Match Speaker: 50watt-300watt (2.1 channel passive speakers or subwoofer)
- Work Temperature: -40°C~85°C
- Work Humidity: 0%~95%RH
- Size: 3.943.940.9 inch
- Weight: 0.46lb/210g
- DC Socket: 5.5*2.1mm
Usage Features:
- Easy Assembly: The boards come with all necessary components for assembly, including acrylic shells, copper columns, screws, steel nuts, screw mats, power cables, screwdrivers, and knobs. The installation process involves attaching the bottom and top acrylic shells, and for some models, a heat sink, followed by installing the volume knob(s).
- Volume Control: Each board features a volume knob. For models with treble and bass control (ZK-502T, ZK-1002T, ZK-TB21), there are additional knobs for these adjustments. It is recommended to adjust the volume switch to the OFF position before inserting the knob, aligning the volume mark to the six o'clock position.
- Speaker Connection: Speakers are connected by loosening the speaker terminals with a screwdriver, inserting the speaker wires, and then securing the screws.
- Power Supply: The choice of power adapter is crucial for optimal performance. Higher voltage and current power adapters lead to better output power and the ability to drive larger speakers. For 100W x 2 output, a power adapter higher than 3A is recommended, and for 50W x 2, higher than 2A. Low voltage or current can lead to distorted sound or insufficient power.
- Bluetooth Connectivity: To connect via Bluetooth, power on the amplifier board, and a blue indicator light will illuminate. Search for "BT-WUZHI" on your device's Bluetooth settings. A beep confirms successful connection. The board will automatically reconnect to the last paired device. Only one Bluetooth device can be paired at a time.
- AUX Input: For wired audio input via the 3.5mm AUX jack, any active Bluetooth connection must be disconnected. After a beep, the audio cable can be inserted to play music. If Bluetooth is connected while an AUX cable is inserted, the input will convert to Bluetooth.
- Treble and Bass Control (ZK-502T, ZK-1002T, ZK-TB21): These models offer dedicated knobs for adjusting treble and bass, allowing users to fine-tune the sound to their preference. It is recommended to turn the treble and bass control switches to the right until the gain is minimal before inserting the knobs.
Maintenance Features:
- Moisture Protection: The amplifier boards are not water-resistant. It is essential to keep them free from moisture to prevent damage.
- Cleaning: Only clean the boards with a dry cloth or tissue. Avoid using liquid cleaners or solvents, as these can cause damage.
- Overheat Protection: In cases of long-time high-power output, the power amplifier board may overheat, triggering its overheat protection. If this occurs, it is advised to turn down the volume or improve heat dissipation to prevent damage.
- Warranty: All Fosi Audio products come with an 18-month limited warranty covering parts and labor from the date of purchase. Users are encouraged to contact Fosi Audio for any problems. The warranty does not cover damage from accidents, misuse, abuse, neglect, excessive moisture, lightning, power surges, other acts of nature, unauthorized modifications or repairs, or failure to follow instructions.
- Shipping for Service: If service is required, users are responsible for shipping charges to Fosi Audio or an authorized dealer. It is recommended to retain original shipping materials for safe transport and to insure the shipment, as Fosi Audio is not responsible for damages incurred due to poor packing during shipping.
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