Signal input mode of power amplifier

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About the signal input mode selection of the power amplifier. In professional audio engineering, we often encounter problems such as signal parallel connection and bridging. First of all, we must clearly understand the significance of selecting the corresponding mode. There is usually a toggle switch or spring button switch on the back panel of the power amplifier. The mode name is marked in English next to the switch. The three modes are: STEREO (stereo, that is, two in and two out), PARALLEL (parallel, that is, one in and two out), and BRIDGE (bridge, that is, one in and one out). Specifically, when there are a large number of speakers and the same audio signal needs to be used, the PARALLEL mode may be used; when the speaker power is large and the power of the single channel of the power amplifier is small, the BRIDGE mode may be used. When selecting the mode, it is recommended that the toggle switch must be repeatedly toggled several times when the power amplifier is turned off, or the spring button switch must be repeatedly pressed several times to ensure that the mode is set correctly. Another point to note is that in some projects, many power amplifiers are needed, but the audio processor has a small number of available output channels, or even no audio processor. This requires a high number of output interfaces for the mixer or audio source device, but in fact the number of available output interfaces is very limited. There are two main solutions that many friends are accustomed to: 1. Use a one-to-many signal line to distribute the signal of an output interface to the input channels of multiple power amplifiers. 2. Input one signal or the main signal to a power amplifier, set each power amplifier to the signal parallel mode (some power amplifiers are designed with a signal parallel output interface next to the signal input interface), and then connect the signal to the next one in turn by hand in hand (because the audio signal parallel function of most power amplifiers is only a mechanical line switching, and no signal processing circuit is designed, which is essentially the same as the principle of using a one-to-many method). It is not unreasonable to adopt the method of one-to-many. In actual engineering applications, this is a very practical and common practice, but the problem is that you can't divide as many as you want, because it is related to the input and output impedance matching factors between audio devices. Usually, one output terminal signal of an audio processor can be divided into up to 3 signals. This data is a reference value based on the input and output impedance matching relationship of most audio devices. It is not an absolute value and should be calculated based on the actual configuration. Appendix: The reference simplified calculation formula is: N=Zin /(10Zout) N is the number of signals that can be divided; Zin is the input impedance of the lower audio device; Zout is the output impedance of the audio device. For example: the output impedance of a device is 660 ohms, and the input impedance of the downstream device is 20K ohms, then N=20000/(10×660)=3.03≈3, that is, one output interface of this audio device can divide up to 3 identical audio signals into the input end of the downstream device. When the number of signal output interfaces is insufficient, the best solution is to add a professional audio signal distributor to avoid problems such as mismatch of input and output impedance of audio devices and signal distortion.