1. Introduction
Thank you for purchasing the OBSBOT VD-AK45Pro Stereo Receiver Amplifier. This compact and powerful 2.0 channel amplifier is designed to enhance your home audio experience with versatile input options including Bluetooth 5.3, USB, SD card, RCA, FM radio, and two microphone inputs for karaoke or public address. Please read this manual carefully before operating the device to ensure proper use and optimal performance.
2. Safety Instructions
- Do not expose this unit to rain or moisture to prevent fire or electric shock.
- Do not open the amplifier casing. There are no user-serviceable parts inside. Refer all servicing to qualified service personnel.
- Ensure proper ventilation around the unit. Do not block any ventilation openings.
- Use only the specified power adapter (DC12V/5A or AC 110V-240V).
- Keep the unit away from heat sources, direct sunlight, and strong magnetic fields.
- Before making any connections, ensure the amplifier is turned off and unplugged from the power outlet.
3. Package Contents
Please check that all items are present:
- VD-AK45Pro Stereo Receiver Amplifier
- Remote Control
- Power Adapter (DC12V/5A or AC 110V-240V, depending on region)
- User Manual (this document)
4. Product Overview
4.1 Front Panel
- Power Switch: Turns the unit ON/OFF.
- USB/SD Port: For playing audio files from USB drives or SD cards.
- LED Display: Shows current mode, track information, or FM frequency.
- Mode Button: Switches between input sources (Bluetooth, USB, SD, FM, RCA).
- Previous Button: Skips to the previous track/station.
- Play/Pause Button: Plays or pauses audio playback.
- Next Button: Skips to the next track/station.
- Cycle Button: Toggles repeat/loop modes for USB/SD playback.
- Treble Knob: Adjusts the high-frequency audio level.
- Bass Knob: Adjusts the low-frequency audio level.
- Microphone Volume Knob: Adjusts the volume of the connected microphones.
- Microphone Inputs (MIC1, MIC2): 6.35mm (1/4 inch) jacks for connecting microphones.
- Master Volume Knob: Adjusts the overall output volume.
4.2 Rear Panel
- FM.ANT: Connector for FM antenna.
- AUDIO INPUT (RCA): Stereo RCA input for external audio sources (e.g., CD/DVD player, TV).
- SPEAKERS OUTPUT (L/R): Terminals for connecting passive speakers (4-16 Ohms impedance).
- AC POWER INPUT (110V/220V): Power input for AC power cord.
- DC 12V/5A POWER INPUT: Alternative power input for DC 12V/5A adapter.
5. Setup Instructions
Before connecting, ensure the amplifier is turned OFF and unplugged from the power source.
5.1 Connecting Speakers
- Identify the left and right speaker output terminals on the rear panel.
- Connect your passive speakers (with an impedance of 4-16 Ohms) to the corresponding terminals. Ensure correct polarity (+ to + and - to -) for each speaker.
- Tighten the terminals securely to prevent loose connections.
5.2 Connecting Audio Sources
The VD-AK45Pro supports multiple input modes:
- RCA Input: Connect external audio devices (e.g., CD/DVD player, TV, game console) to the RCA AUDIO INPUT jacks on the rear panel using an RCA cable.
- USB/SD Card: Insert a USB flash drive or SD card containing MP3/WMA audio files into the respective port on the front panel.
- FM Antenna: Connect the provided FM antenna (or an external FM antenna) to the FM.ANT terminal on the rear panel for radio reception.
5.3 Microphone Connection
Connect up to two microphones to the MIC1 and MIC2 input jacks on the front panel. Adjust the Microphone Volume knob to control the microphone level.
5.4 Power Connection
Connect the power adapter to the appropriate power input on the rear panel (either AC 110V-240V or DC 12V/5A) and then plug it into a wall outlet.
6. Operating Instructions
6.1 Power On/Off
Press the Power Switch on the front panel to turn the amplifier ON or OFF. The LED display will illuminate when the unit is powered on.
6.2 Input Selection
Press the Mode button on the front panel or the remote control to cycle through the available input sources: Bluetooth (BT), USB, SD, FM, and RCA.
6.3 Volume Control
Rotate the Master Volume knob on the front panel clockwise to increase volume and counter-clockwise to decrease it. You can also use the volume buttons on the remote control.
6.4 EQ Controls
- Treble Knob: Adjust to increase or decrease high-frequency sounds.
- Bass Knob: Adjust to increase or decrease low-frequency sounds.
- Microphone Volume Knob: Adjust the volume level of the connected microphones.
6.5 Bluetooth Pairing
- Press the Mode button until "BLUE" or "BT" appears on the LED display. The amplifier is now in Bluetooth pairing mode.
- On your mobile device (smartphone, tablet, computer), enable Bluetooth and search for available devices.
- Select "VD-AK45Pro" from the list of devices.
- Once paired, you will hear a confirmation tone, and the LED display will indicate a successful connection. You can now stream audio wirelessly.
6.6 USB/SD Playback
After inserting a USB drive or SD card, the amplifier will automatically switch to USB/SD mode and begin playing audio files. Use the Previous, Play/Pause, and Next buttons to control playback. The Cycle button can be used to toggle repeat modes.
6.7 FM Radio
- Press the Mode button until "FM" appears on the LED display.
- Use the Previous and Next buttons to manually tune to radio stations.
- For automatic scanning, press and hold the Play/Pause button. The amplifier will scan and save available stations.
6.8 Remote Control Usage
The included remote control allows convenient operation from a distance. It provides access to input mode selection, volume control, track navigation, play/pause, and EQ adjustments.
7. Specifications
| Feature | Specification |
|---|---|
| Model Number | VD-AK45Pro |
| Channels | 2.0 (Stereo) |
| RMS Power Output | 50W x 2 (100W total RMS) |
| Maximum Peak Power Output | 400W x 2 (PMPO) |
| Input Modes | RCA, Bluetooth 5.3, USB, SD Card, MIC, FM |
| Speaker Impedance | 4-16 Ohms |
| Bluetooth Range | Up to 33 ft / 10 m |
| Total Harmonic Distortion (THD) | ≤ 0.1% |
| Signal-to-Noise Ratio (SNR) | 92dB |
| Power Adapter | DC12V/5A or AC 110V-240V |
| Net Weight | 690g (1.52 lb) |
| Dimensions (L x W x H) | 180 x 138 x 65 mm (7.1 x 5.44 x 2.56 in) |
8. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No power | Power cable not connected or power outlet faulty. | Check power connections. Try a different outlet. |
| No sound output | Incorrect input selected, speaker wires loose, or volume too low. | Ensure correct input mode. Check speaker connections and polarity. Increase Master Volume. |
| Bluetooth pairing fails | Amplifier not in pairing mode, device too far, or interference. | Ensure amplifier is in BT mode. Move device closer. Turn off other Bluetooth devices. |
| USB/SD playback issues | Unsupported file format, corrupted files, or card/drive not properly inserted. | Ensure files are MP3/WMA. Reinsert USB/SD. Try a different USB/SD. |
| Poor FM reception | Antenna not connected or poor signal. | Connect FM antenna. Adjust antenna position for better reception. |
| Microphone not working | Microphone not connected, Mic Volume too low, or microphone faulty. | Ensure microphone is securely plugged in. Increase Microphone Volume. Test with another microphone. |
9. User Tips
- Understanding Power Ratings: The amplifier is rated at 50W x 2 RMS (Root Mean Square) power, which is the continuous power output. The 400W x 2 mentioned is typically PMPO (Peak Music Power Output), representing the maximum instantaneous power. For consistent performance, refer to the RMS rating when matching with speakers.
- Optimal Speaker Matching: For best sound quality and to prevent damage, ensure your speakers have an impedance between 4 and 16 Ohms.
- Bluetooth Range: While the amplifier supports Bluetooth 5.3 for stable connections, environmental factors like walls and other wireless devices can affect the 33 ft (10m) range. Keep your paired device within line of sight for optimal performance.
- Remote Control Battery: If the remote control is unresponsive, check and replace its battery.
10. Maintenance
- Cleaning: Use a soft, dry cloth to clean the exterior of the amplifier. Do not use liquid cleaners or aerosols.
- Ventilation: Ensure the ventilation openings are free from dust and obstructions to prevent overheating.
- Storage: If storing the unit for an extended period, unplug it from the power source and store it in a cool, dry place.
11. Warranty and Support
For warranty information or technical support, please refer to the seller's policy or contact the retailer where you purchased the product. Keep your purchase receipt as proof of purchase.
