(ZK-502MT/ZK-502T Bluetooth Audio Amplifier)
Question and answer:
1. How to choose a power supply?
The power supply with the board is critical. The higher the voltage, the higher the current and the better the output power. If you only have 12V 1A, you can bring a 3-4 inch speaker. If you are 19V 5A or above, there is no problem with 8-10 inches, and the power supply must be highly valued. If the voltage is too low, the sound will be distorted after the sound is amplified. If the current is too small, the speaker will pull the voltage low, work abnormally or the sound quality will deteriorate.
It is recommended to use 18V19V24V power supply with current above 3A. If you only have 9V12V or 1A 2A power supply, it can also be used but the power is small. Please pay attention to the maximum volume when using it, which may affect the sound quality.

2. How to choose a speaker?
Commonly used speakers are generally 4 ohms or 8 ohms, can not distinguish between positive and negative, the effect is the same.If your speaker power is small, it may be used between 10W-30W. The power supply voltage is small to prevent the amplifier from burning out after burning. For example, select a power supply below 15V.
If you are a 50W-100w speaker, don't worry about the speaker burnout. You can choose 12-24V power supply. The higher the voltage you choose, the louder the output sound or power.The speaker power is not recommended to exceed 100W, otherwise the sound quality will be affected.

3. Introduction of audio input mode
This audio amplifier module has two audio input modes: 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 is bluetooth mode, and bluetooth mode support automatic connection.AUX insertion is AUX mode when bluetooth is connectionless.It is important to make sure that the bluetooth connection of this module has been disconnected when using AUX mode.

4. How to adjust the bass and high pitch?
The BASS potentiometer in the middle is to control the BASS, the right BASS is enhanced, the left BASS is attenuated.When the potentiometer is in the middle position, the bass is neither enhanced nor attenuated.
The TREBLE potentiometer on the left controls the TREBLE. the right TREBLE enhanced and the left TREBLE attenuated.When the potentiometer is in the middle position, it does not increase or decrease the treble.
Note when adjusting treble and bass: when the treble or bass right rotation is adjusted to the maximum, if the sound is distorted, it means that the treble or bass gain is too large. It is necessary to turn the treble or bass potentiometer to the left to reduce the gain or turn the VOLUME potentiometer to the left to reduce the total volume.

5. When the sound becomes louder, the phenomenon of turbid sound appears.
The sound is distorted. Please change the adapter power supply with a higher voltage rating.

6. After the sound becomes louder, the sound is stuck.
The input power is insufficient, and the power supply itself is intermittently powered off. Please replace the power supply with a larger power.
Or the output power is too large, the power amplifier board is seriously heated, and thermal protection occurs, reducing power usage or enhancing heat dissipation.
 
7. What are the factors related to the sound quality?
Sound quality is not only related to the amplifier module, but also to the sound source and the entire 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, speaker and the surrounding environment.Sound quality is best only when the sound source, amplifier module and speaker are matched.

(DY-AP3001 Power Amplifier)
Features:
10W/20W/30W Class-D audio power amplifier module Wide supply voltage range 12V/24V DY-AP3001

NOTE：
1、8~24VDC is recommended; upper than 26V, it will be damaged.
2、Driving 4Ω load, power supply must be under 16V; and driving 8Ω load, supply must be under 24V.
3、The supply current must be 2A at least.
4、Inverting power supply is not permitted, or the chip will be damaged.
5、The module is designed for audio signal range 0.5V~1.5V.
6、The line connecting speaker with module should be within one meter.
7、ESD protection , please release ESD on your hands before you contact the module.
8、30W and upper power speaker is recommended.