What is called balanced transmission?
Before we introduced the various wires commonly found in home theater systems: "Common Home Theater Signal Line Classification and Connection Usage", here is a brief introduction to balanced transmission. Balanced transmission is a very widely used method of audio signal transmission. It uses the principle of phase cancellation to minimize other interference during audio signal transmission. It requires three wires in parallel, namely ground, hot, and cold. Therefore, the balanced input and output plug-ins must have 3 pins, such as Canon or a big three-core plug-in. The transmission line must of course be a 2-core 1 shield layer. Since the hot end signal line and the cold end signal line are relatively close in the same shield layer, other interference signals received during transmission are almost the same. However, the phase of the transmitted hot-end signal and the cold-end signal are opposite, so the hot-end signal and the cold-end signal are subtracted at the input of the next-stage device, the same interference signal is cancelled, and the transmitted signal is not in phase. Will lose. Therefore, the balanced transmission method is usually used in professional situations and when the transmission distance is relatively long.
The difference between balanced transmission and unbalanced transmission
The balanced transmission signal transmission line has two inputs and one ground. An unbalanced transmission signal transmission line has an input and a ground.
When there is common mode interference, since the interference signals received by the two terminals of the balanced transmission are similar and the polarities are opposite, the interference signals can cancel each other out in the balanced transmission load, so the balance circuit has better anti-interference. ability.
(Tianyi AD-3D pure class A HIFI amplifier)
Common applications for balanced transmission
Balanced transmission is usually used in long transmission distances and more professional occasions. The high-end equipment in the field of civil audio is connected to the audio source and the power amplifier, and the front-to-back connection of the power amplifier is usually balanced.
What is the difference between balanced and unbalanced interfaces?
The difference in signal size is the difference between the MIC signal and the LINE signal, not the difference between balance and imbalance.
In order to see and hear, then spread the basics:
Balance imbalance is just an output input wiring method, regardless of the signal size, just like a wire, the plug has a round and square, and there are various metamorphosis, but it has nothing to do with the current and voltage inside.
Balance is to divide the output signal into two, half of which is reversed by PAHSE, and then output through two signal lines respectively, there will be electromagnetic interference on the signal line, and then the signal that is reversed at the receiving end will pass another The transmitter, rewinding and superimposing the signal with no other backwards to get the original signal, and the interference signal during transmission will be eliminated due to the PHASE effect, thus obtaining a clean signal, which is why the imbalance cannot exceed 10 to 15 meters. And the reason why the balance line can exceed 500 meters.
+4dBu is the studio recording standard signal voltage is 1.23V
-10dBv is the home recording standard signal (including HIFI), the voltage is 0. 32V
Whether it is dBu or dBv, you can use balanced or unbalanced interface, just like your TV plug and computer plug can be different.
Everyone puts the MIC or something on the LINE IN of the mixer and plugs it into the XLR interface. The volume is very different, because the amplification circuits behind the two interfaces are different. Why are different amplifier circuits not uniform?
Here, I am forced to popularize a concept. The analog sound signals we usually transmit are as follows.
Microphone signal: It is the signal from your microphone. This signal is very weak. (I can imagine a dynamic MIC, the energy that you talk to, the circle on the diaphragm, the movement in the magnet, how much electricity can be sent Come?) If it is big, if there are dozens of people, if the tuner accidentally takes the MIC plug, it will not be electrocuted. The voltage strength of this signal is about 1MV.
LINE signal. That is, the usual audio signal, which comes out of your CD player, from your mixer, from your sound card, from your effects, as long as the LINE OUT is written, it is the LINE signal. This intensity is around 1 to 4V.
Musical instrument signal, the instrument here is not a piano or a violin, it is your electric guitar, electric bass or something. This year, the puller knows that the guitar can't enter the console. If you want to enter, you have to go through a DI box. Why? High impedance, HI-ZI, I am not here to play the ghost, no matter how, the instrument signal is very small, but it is an unbalanced interface (who has seen the XLR interface guitar), there are two coils in the DI box Through a physical method that is simple but I am lazy, I split a weak guitar signal into two reverse signals, which are output from the XLR port to the XLR input of the mixer.
Ok, seeing everyone here understands, how can a 1 millivolt microphone signal or guitar signal be level with the LINE signal of 1 to 4 volts on the mixer? So the amplification circuit behind the XLR is better than The amplification circuit behind LINE is powerful. This question is already explained clearly enough. Coupled with the plug-in diagram given by the East China brother, I believe there is no problem, right?
Also add a little more:
What happens when you connect between the balanced and unbalanced ports, under what circumstances there will be no sound, under what circumstances the sound will be reversed, and under what circumstances will the sound become smaller?
From the balance port, with the properly soldered balance line, sent to the unbalanced input, the signal will lose half.
From the balance port, with the unbalanced line, it is sent to the unbalanced input, and the signal is also lost by half.
From the balance port, the balance line that is reversed is sent to the unbalanced input, and the signal loss is half and reversed.
From the unbalanced port, use the correctly welded balance line to send to the balanced input, the signal is unchanged.
From the unbalanced port, the unbalanced line is sent to the balanced input, and the signal is unchanged.
From the unbalanced port, the balanced line that is reversed is sent to the balanced input, and there is no sound.
The specific reason is why everyone thinks about it.
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