ZK-TB21 TPA3116D2 bluetooth 5.0 Subwoofer Amplifier Board 50WX2+100W 2.1 Channel Power Audio Stereo Bass AMP

  Availability: In Stock
  Shipping: Free Airmail 
  Estimated Delivery: 
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  •   Shipping Methods

    Handling Time

    Before we can ship your order, we prepare your products, do strict quality-control tests and carefully package the items. The time it takes to prepare your items for shipping is separate from the delivery time. It usually takes 1-3 business days to ship out .

    Shipping Methods

    You can choose the preferred shipping method on the cart page during the checkout process. We offers 3 international shipping methods:

    1. Airmail – Free untracked economy shipping via national postal services (HK Post, Singapore Post, China Post, PostNL, Swiss Post, Sweden Post, USPS, Royal Mail e.t.c.)
    2. Airmail Registered – Tracked shipping via national postal services (HK Post, Singapore Post, China Post, PostNL, Swiss Post, Sweden Post, USPS, Royal Mail e.t.c.)
    3. Expedited Shipping – Express shipping with courier delivery (DHL, UPS, FedEx, TNT)

    Delivery Time

    Airmail and Airmail Registered Area Estimated Delivery Time
    United States, Canada 7-25 business days
    Australia, New Zealand, Singapore, United Arab Emirates 10-25 business days
    United Kingdom, France, Spain, Germany, Netherlands, Japan, Belgium, Denmark, Finland, Ireland, Norway, Portugal, Sweden, Switzerland 10-25 business days
    Italy, Brazil, Russia, South Africa 10-45 business days
    Other countries 10-35 business days
    Expedited Shipping 3-10 business days to Worldwide

    Note: If you choose an expedited shipping, please remember to leave a valid contact number, this is required for expedited shipping’s courier delivery.

  •  Returns & Refund

    Last updated October 05, 2022


    If you are not completely satisfied with your purchase for any reason, you may return it to us for a full refund within 15 days from delivery date. All returned items must be in new and unused condition, with all original tags and labels attached.

    Return Process

    To return an item, please email our customer service at sales@alexnld.com to obtain a Return Merchandise Authorization (RMA) number. After receiving a RMA number, place the item securely in its original packaging, and mail your return to the following address:

    Alex NLD
    Attn: Returns
    RMA #
    HaGiborim St 8
    Tiberias, 14388

    Please note, you will be responsible for the return shipping charges. We strongly recommend that you use a trackable method to mail your return.

    All customers should contact us and obtain Return Merchandise Authorization (RMA) number before sending anything to us. We will not be responsible for returned item(s) without notifying us in advance.


    After receiving your return and inspecting the condition of your item, we will process your refund to the credit / debit card or PayPal account which was used to place the original order.

    Please allow at least seven (7) days from the receipt of your item to process your refund. Refunds may take 1-2 billing cycles to appear on your credit card statement, depending on your credit card company. We will notify you by email when your refund has been processed.


    If an item is found damaged or defective on receipt, we kindly ask you to contact us within 15 days from the delivery date to arrange a refund or exchange without physical return of the item.

    Please provide us with following:

    1. Photos of the front and back sides of the packaging box;
    2. A photo, video or screenshot of the defective item or the defective part of the parcel.

    Our customer service team will communicate with you to arrange a refund or reshipment without physical return of the item.

    Warranty & Repair service

    If any of the items you have purchased from us is found defective within 1 year from receipt, you are entitled to a repair under warranty. Please kindly provide us with evidence photos or videos of the defective item. After providing such information to our Customer Service team  and the problem is acknowledged, you can send the items back to us for a repair.

    Note:  Please be aware, we do not cover the cost of the returns fees in  warranty & repair service.

    Order Cancellation

    If you want to cancel an order within 24 hours from confirmation of the payment, you will be entitled to a full refund. It is still possible to cancel an order after 24 hours, provided that it has not yet been shipped. If an order has been shipped, it’s impossible for us to cancel or modify it anymore. If you still want a refund, you required to return the item on it’s arrival.


    If you have any questions concerning our return policy, please contact us at:

    +972 054-536-2888



Item Type: Amplifier Board
Model: ZK-TB21
Material: electronic components
Color: Black
bluetooth Version: 5.0(no shielding, 10m)
Input sensitivity: 500mV
Audio Input: AUX+Bluetooth
Channel: 2.1
Chip: TPA3116D2(with AM anti-interference function)
Power: DC12-24V/5A
Adapter speaker: 20-100W, 4-8Ω
Output power: Max.50W(R and L channel), Max.100W(subwoofer)
Quantity: 1 Pcs

Package included:

1 x Amplifier Board(not include shell)

Question and answer:

1. How to choose the power supply?
The power supply with the board is very key, the selected power supply ripple must be small, ripple large power supply will lead to power amplifier bottom noise, there is a current sound.The higher the voltage, the higher the current, and the higher the power output. If you only have 12V 1A, you can have 3-4 inch speakers.If you are above 19V 5A, no problem with 8-10 inches, power must be highly valued.If the voltage is too low and the sound is amplified, it will easily cause sound distortion. If the current is too low and the horn cannot be brought up, the voltage will be pulled down, which will lead to abnormal operation or poor sound quality.
It is recommended to use 18V19V24V power supply with current above 5A.If you only have 9V12V or 1A 2A power supply, you can also use it but with low power. When using it, choose the volume close to the maximum, which may cause distortion and affect the sound quality.
2. How to select speakers?
About the speaker type: commonly used speakers are generally 4-8 ohms, can be used.Speakers in left and right channels need to be connected to full frequency or medium and high frequency speakers with power between 20W and 100W.Subwoofer speakers cannot be connected to ordinary speakers. Speakers with subwoofer speakers should be connected, with power between 20-100W.The subwoofer horn must have a dive frequency of at least 50Hz.
If your speaker power is small, such as between 20W-50W can also be used, the power supply voltage needs to be small, to prevent the loudspeaker burnt after loud, such as choose power below 15V.If you are a 50W-100W speaker, you don’t have to worry about burning out the horn. You can choose a 12-24V power supply. The higher the voltage you choose, the more sound or power you can output.Speaker power is not easy to exceed 100W, otherwise it will affect the sound quality.
3. Audio input mode
There are two audio input modes for this audio amplifier module: one is Bluetooth input and the other is AUX input. Bluetooth mode is preferred.Bluetooth can be connected in either mode.As long as the Bluetooth connection is successful, it is bluetooth mode, and bluetooth mode supports automatic back up.AUX insert is AUX mode when Bluetooth is disconnected.The bluetooth connection of this module is disconnected when using AUX mode.
4. How to adjust the main volume?
The MAIN – VOLUME knob is used to adjust the MAIN VOLUME.The right main volume goes up and the left main volume goes down.The master volume affects both the left and right channels and the subwoofer volume.
5. How to adjust the height and bass of the left and right channels?
R&L CHANNEL – BASS knob is for BASS, right-handed BASS enhancement, and left-handed BASS attenuation.When the knob is in the right-most position, it does not enhance or attenuate the bass.
The R&L CHANNEL – TREBLE knob is used to control the TREBLE, with right-handed TREBLE enhancement and left-handed TREBLE attenuation.When the knob is in the middle, it does not enhance or attenuate the treble.
Note when adjusting high and low sounds: when the TREBLE or BASS sounds are right-rotated to near maximum, if the sound distortion is distorted, the gain of the TREBLE or BASS sounds is too large. It is necessary to turn the TREBLE or BASS knob to the left to lower the gain or turn the MAIN-VOLUME knob on the right to the left to reduce the total VOLUME.

6. How to adjust the subwoofer?
SUBWOOFER – VOLUME controls the VOLUME of the SUBWOOFER.The right-handed volume goes up and the left-handed volume goes down.
The SUBWOOFER – FREQ knob controls the cutoff frequency of the SUBWOOFER.The right frequency increases and the left frequency decreases.The frequency adjustment range is 20HZ-200Hz.
7. It’s ok to have a small voice, but after the voice becomes louder, there will be the phenomenon of sound turbidity.
The sound is distorted, please turn down the total volume or change the adapter to a higher voltage leveel.
8. It’s ok to have a small voice, but when the voice gets louder, there will be the phenomenon of sound lag.
If the input power is insufficient and the power is protected by its own intermittent power failure, please replace the power with a more powerful one.Or the power is too big, the power amplifier heating seriously, appeared the heat protection situation, reduce the power use or strengthen the heat dissipation.
9.What factors are associated with sound quality?
The quality of sound is not only related to the power amplifier module, but also to the power supply, sound source and the whole sound system.Basically every link of the sound system will affect the sound quality, among which the main link is the audio transmission line, audio power supply, tone circuit, amplifier circuit, speakers and the surrounding environment.The sound quality is best when the sound source, power supply, amplifier module and the speaker are matched.


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