ZK-502E 50W*2 High and Bass Adjustment Preamp Audio Power Amplifier Module Subwoofer Bluetooth 5.0 Dual-channel Stereo with Aluminum Shell

$61.99
  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

    Returns

    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
    Israel

    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.

    Refunds

    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.

    Exceptions

    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.

    Questions

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

    +972 054-536-2888
    sales@alexnld.com

     


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Specifications:

Input power: voltage DC12-24V, current above 5A
Amplifier output: MAX 50W*2 @24V/4ohm
Speaker parameters: 4-8ohm; 20-100W
Input sensitivity: 800mV
Signal to noise ratio: >90dB
Frequency response: 20Hz-18KHz
Bare machine size: 103mm*88mm*30mm (not including the height of the knob seat)
Package weight: about 335g
Packing size: about 160*155*73mm

Instructions:

1. Connect the power amplifier output to the speaker or speaker, R connect to the right channel, and L connect to the left channel (note that the polarity of the speaker is not reversed, the sound will be muddy if it is reversed).
2. Connect to the power supply (the power supply can only be connected to direct current, the voltage should not exceed 25V, and the nominal 24V battery pack should not be connected).
3. Turn the volume knob clockwise to turn it on, there will be a Bluetooth notification sound, and the blue light flashes at this time.
4. Choose the audio input mode that suits you to input audio. The audio input mode can only be selected from one of three, and cannot be activated at the same time. The audio input mode can be automatically recognized (automatically recognized with priority, USB input>AUX input>Bluetooth input), or manually switched (when multiple audio is connected at the same time, long press the pause/play button to switch the audio input mode) .
5. Rotate the volume knob, treble knob, and bass knob to adjust the volume and treble and bass gain to appropriate positions.

Package includes:

1 x Amplifier Module

Common problem:

Q1: All the wires are connected, why the indicator light is not on?
A1: Rotate the volume switch to turn it on. If it still does not light up after turning on, check whether the power supply is connected properly and whether the positive and negative poles of the power supply are connected correctly. If everything is right, find a laptop power adapter (power supply should not exceed DC25V) or 12V battery power supply to determine whether it is a power supply problem or a product problem.
Q2: Why is the sound broken or distorted?
A2:
1). The power supply voltage is too low, the volume is adjusted too much, the power supply is insufficient, and the sound will be distorted. It is recommended to change to a high-voltage power supply or turn down the volume.
2). The power supply is sufficient, but the speaker power is too small, which will cause the speaker to overload and break the sound. It is recommended to turn down the volume or replace with a higher-power speaker.
Q3: Why does the volume knob do not move, but the sound level is different when connecting to different audio sources (such as first connecting a CD and then changing to a mobile phone)?
A3: If the volume knob is not moved, the sound magnification will not change. The amplitude of the audio signal output by different playback devices is different. For example, the mobile phone is usually 0.35mV, and the CD is 1V, so the sound level is naturally different.
Q4: Why is there a loud current noise from the speaker?
A4: The loud current sound in the speaker has a lot to do with the power supply. The output ripple of many power adapters on the market is too large, which will interfere with the work of the power amplifier and cause loud current noise. Test it with a 12V battery. If the current noise is significantly reduced, it is a power supply problem. It is recommended to replace the power adapter with low output ripple or use a battery for power supply.
Q5: Why is there a loud buzzing sound in the speaker when one end of the AUX audio input line is connected to the product and the other end is not connected to the audio source?
A5: When the unshielded signal line is used, the audio line is equivalent to an antenna, which will receive electromagnetic waves in the air, and then send it into the amplifier for amplification. If you hate this sound, it is recommended that you replace it with a shielded line Signal cable or unplug the signal cable.
Q6: How to judge the noise floor of the machine?
A6: The noise floor has a lot to do with the quality of the power supply, the quality of the input audio, and the on-site use environment. The most standard way of judging is to connect to Bluetooth and play music with the smallest sound, with ears 0.5 meters away from the speakers, whether you can hear obvious low noise. If there is no obvious bottom noise, it is normal. If there is an obvious bottom noise, it is abnormal.
Q7: Why does the AUX interface make a ‘click’ when plugging or unplugging the audio cable?
A7: Because the AUX input adopts the lossless input of signal relay switching, the sound of ‘click’ is the sound of relay action. This is a normal sound, not a problem with the product.
Q8: Can the USB port provide external power supply?
A8: No, the USB interface can only be connected to a U disk or a computer USB interface.
Warning!!
1. Do not open the shell privately, as improper operation may damage the product.
2. Please use the switching power supply of a regular manufacturer, otherwise there is a risk of damage to the machine.
3. Do not use the machine in a high temperature and high humidity environment.
4. Before DIY, please make sure you have enough basic knowledge of electronics.

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