Amplifier knob to the far right may make your speaker explode in place!

- Jun 30, 2020-

In fact, the power amplifier knob is not the main reason for howling, but with it we can optimize the system to further avoid howling, and the power amplifier knob is also closely related to our dynamics, signal-to-noise ratio, etc., so today we will study together, What is the power amplifier knob.


When it comes to the power amplifier knob, many people will say that it is to adjust the power of the power amplifier. Strictly speaking, this statement is not correct, because the power of the power amplifier is fixed. If you turn the knob a little bigger, the power will not change. The size, do you think the power of the power amplifier will become larger when the knob is turned larger?

In fact, the power amplifier knob is just a potentiometer, a variable resistor, the main role is to attenuate the signal voltage input to the power amplifier. In fact, when we adjust this knob, we are adjusting the size of the input signal. When the knob is turned to the left, the potentiometer completely attenuates the signal input to the power amplifier. When the knob is turned to the right, the potentiometer does not attenuate the input signal, which is equivalent to the potentiometer no longer existing.


Is this power amplifier knob amplifying and attenuating the input voltage?


That's wrong, this power amplifier knob can attenuate the voltage, but TM can't amplify the voltage, it's just a resistor!

The signal (analog signal) that we usually talk about is actually a voltage signal. Usually these upstream devices such as the mixer processor output a voltage (signal) of about 1V to the power amplifier. After receiving this voltage, the power amplifier is responsible for converting this signal. The voltage is amplified, the current is also amplified, and finally the signal is amplified to power, and then output to the speaker, pushing the speaker unit.

This signal of about 1V comes to the front of the power amplifier knob. Does the signal dare to pull it up? As early as TM, I’ve counseled him, OK, he is a social person, he can cut you directly and attenuate the signal. Or simply kill you, and attenuate the signal directly.

But because the power amplifier knob is just a resistor, it cannot amplify the signal, but it can act as a thug, helping you attenuate the input voltage.


Does the power amplifier knob have any relationship with the amplified voltage?


That's not it! When the power amplifier knob attenuates the input voltage, it will be sent to the next stage of the circuit for amplification, but after the power amplifier design is formed, the voltage amplification factor is fixed. Therefore, the greater the voltage sent to the next stage of the circuit, the greater the voltage output by the amplifier. When the voltage sent is smaller, the output voltage of the power amplifier is also smaller. Therefore, the power amplifier knob also affects the voltage amplification, but it is not amplified by itself, but sent to the next stage of amplification.


Is the larger the output voltage of the power amplifier, the greater the power?


Someone finally got it right!

As mentioned earlier, the power amplifier amplifies both the voltage and current of the input signal, and finally outputs power.

What is power?


Power = Voltage X Current


What a profound and simple physical law, we want to turn the signal into power, we must grasp both the voltage and the current, and turn the 1V voltage that is too small to become the power that can ignite your speaker.


Oh, it turns out that the power amplifier knob is also related to power? Then we should try to send the voltage to a larger point to make the amplifier output more power?


That will definitely not work. I repeat: the power of the power amplifier is fixed. When the voltage input to the power amplifier reaches a certain point, the power amplifier will output full power and give you all the power that can be given. At this time, if the input voltage is lost again, the power amplifier will be overloaded and clipped, the power amplifier protection will be lighter, and the power amplifier speaker will explode in place together.


Therefore, there is another parameter on the power amplifier called sensitivity, which has two standards of 0.775V and 1.4V. There is usually a switch on the back of the power amplifier to switch different sensitivity. This sensitivity means that when the input voltage to the power amplifier reaches 0.775V or 1.4V, the output power of the power amplifier reaches the maximum JB. If the sensitivity of the power amplifier is set to 1.4V, then the maximum voltage TM that your power amplifier knob can send to the next stage circuit is only 1.4V.


Then do we usually turn the power amplifier knob to the maximum, so that the voltage can reach 1.4V lightly?


In this way, you can easily die, is this 1.4V you dare to achieve at will? That means all the energy of the sound system, boss. If you bring hundreds of speakers to a big toilet for a performance, you can just let out the energy of the entire system and deafen the audience.


The sound system and the performance venue generally have the following three relationships.


The first is that the budget is not enough, the venue is big, and the sound power is not enough.


Second, the budget is okay, the speaker amplifier has enough belts, the audio power can be used for performances, and there is also power margin, performance drops.


The third is that the budget is too much. I brought dozens of speakers in the past and made a profit.


Let me talk about the first one. The audio power is not enough. This has nothing to do with the power amplifier knob. Even if you twist the knob, you can’t save you. There is only one way to ask the organizer to give more money to the speaker amplifier.


The second and third cases are relatively better, the audio power is too large, we can turn off some amplifiers, or try to turn down the amplifier knob first!


Why?


Do you remember the sensitivity 1.4V? When the power amplifier circuit receives a 1.4V signal, it will be fully loaded (assuming that the power amplifier sensitivity is set to 1.4V) and will release all the energy.


What are you doing when you are tuning a big show? Is controlling a monster with a huge volume! And you can use the voltage range of 0V ~ 1.4V in the power amplifier knob to control the size of this monster. This 1.4V is like a ruler to help you measure the size of this monster.


We can attenuate the voltage from the mixer by turning the knob of the power amplifier, and control the voltage to a suitable range, so that the system volume can meet the performance requirements. (Ignore the processor first)


Suppose you bring an audio system with a total power of 10,000W this time, but when you audition you find that the audio is very powerful and overpowering. You played music during the audition and found that the main output level of the mixer was very small and only lost, but the volume of the sound came out super scary.


Obviously, your audio power is too high. You can't use up the power of this set of audio. You can only use some of the power. But this is definitely not a bad thing. It means that the power margin of our system is sufficient. I can give it as loudly as you want! (But if the power is too high, you have to turn off some amplifiers)