Getting rid of extraneous noise in the audio path
Hello!
Guys, this is my first post, and I want to dedicate it to the problem of emerging noise in the audio section.
In the wiring diagram of audio equipment, when any sound reproducing equipment and an active speaker system are connected to two different sockets with grounding, a “parasitic earth circuit” appears in the equipment power supply circuit.
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Grounding / zeroing in buildings is usually done in one place, on the basement or in the basement. The protective contacts of all power outlets installed in the building must be connected to this earth ground. If all equipment is connected to the mains through a single outlet, then there is no problem. It occurs when devices that are electrically connected to each other (for example, a computer and an active speaker system) are connected to the mains through different sockets. Due to the inequality of the resistance of the connections to the ground in the ground loop formed by interconnected devices, a current flows, which creates a background superimposed on the useful signal.
Anyone who has experience with audio equipment is familiar with a loud background that occurs in loudspeakers when connecting equipment and turning it on in operation mode. Computer hardware is no exception, since it also has an AC power source. With improper grounding in case of violation of proper isolation of signal circuits from power supply circuits, noise is interfered with in the form of a useful signal and background AC current.
In the circuit of any electronic device, including audio equipment, all voltages are “tied” to the internal earth of the circuit, the potential of which is assumed to be zero, and all voltages are measured relative to the internal earth of the circuit. This makes it possible to extract the useful signal from the background noise.
When connecting electronic devices with a signal cable, the ground conductor of the cable connects their inner lands, equalizing their potential. This so-called signal ground may not be tied to the potential of the earth, as is the case in the equipment grounding circuit, but the signal circuits of all radio-electronic devices interconnected are tied to one common reference potential.
Unfortunately, the connection of electronic devices between them is fraught with the danger of a parasitic ground loop. If there are several connections in the circuit of interconnected radio-electronic devices to the grounding point through the power supply network, as a result of the dissimilarity of their resistance, a parasitic grounding circuit carries current that creates a noise (background) of 50 Hz in the signal cables connecting the audio equipment, which act as radio antennas .
The most common cause of the background power network are parasitic equipment grounding loops. In the power supply cable of any electronic device, there is a third, grounding wire that connects the device to the common ground point of electrical equipment in the building through a power plug and socket. Connecting all devices that are interconnected by signal cables to the mains through one power outlet reduces the likelihood of parasitic ground loops, although it does not eliminate it completely.
The easiest and most reliable way to get rid of network interference is to connect all equipment to the network through one common power outlet. If it is not possible to completely eliminate the background of the network in this way, then the following two methods of dealing with the network background are used. If you know how to use a soldering iron, unsolder the ground wire (screen) at one end of the signal cable from the connector (at one and not at both ends, since the screen provides protection from radio interference!).
The most effective way is to disconnect one of the devices (for example, a laptop) from the common ground circuit through the power supply network (using an adapter from a three-contact plug to a two-contact plug, or use an extension cord without grounding) using an adapter. But you should not do this for all devices at the same time, as in this case, the “floating potential of the earth”, which is life-threatening, may appear on the body of the equipment.
Guys, this is my first post, and I want to dedicate it to the problem of emerging noise in the audio section.
In the wiring diagram of audio equipment, when any sound reproducing equipment and an active speaker system are connected to two different sockets with grounding, a “parasitic earth circuit” appears in the equipment power supply circuit.
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Some Physics
Grounding / zeroing in buildings is usually done in one place, on the basement or in the basement. The protective contacts of all power outlets installed in the building must be connected to this earth ground. If all equipment is connected to the mains through a single outlet, then there is no problem. It occurs when devices that are electrically connected to each other (for example, a computer and an active speaker system) are connected to the mains through different sockets. Due to the inequality of the resistance of the connections to the ground in the ground loop formed by interconnected devices, a current flows, which creates a background superimposed on the useful signal.
Noise and Background AC
Anyone who has experience with audio equipment is familiar with a loud background that occurs in loudspeakers when connecting equipment and turning it on in operation mode. Computer hardware is no exception, since it also has an AC power source. With improper grounding in case of violation of proper isolation of signal circuits from power supply circuits, noise is interfered with in the form of a useful signal and background AC current.
In the circuit of any electronic device, including audio equipment, all voltages are “tied” to the internal earth of the circuit, the potential of which is assumed to be zero, and all voltages are measured relative to the internal earth of the circuit. This makes it possible to extract the useful signal from the background noise.
When connecting electronic devices with a signal cable, the ground conductor of the cable connects their inner lands, equalizing their potential. This so-called signal ground may not be tied to the potential of the earth, as is the case in the equipment grounding circuit, but the signal circuits of all radio-electronic devices interconnected are tied to one common reference potential.
Unfortunately, the connection of electronic devices between them is fraught with the danger of a parasitic ground loop. If there are several connections in the circuit of interconnected radio-electronic devices to the grounding point through the power supply network, as a result of the dissimilarity of their resistance, a parasitic grounding circuit carries current that creates a noise (background) of 50 Hz in the signal cables connecting the audio equipment, which act as radio antennas .
The most common cause of the background power network are parasitic equipment grounding loops. In the power supply cable of any electronic device, there is a third, grounding wire that connects the device to the common ground point of electrical equipment in the building through a power plug and socket. Connecting all devices that are interconnected by signal cables to the mains through one power outlet reduces the likelihood of parasitic ground loops, although it does not eliminate it completely.
How is it treated?
The easiest and most reliable way to get rid of network interference is to connect all equipment to the network through one common power outlet. If it is not possible to completely eliminate the background of the network in this way, then the following two methods of dealing with the network background are used. If you know how to use a soldering iron, unsolder the ground wire (screen) at one end of the signal cable from the connector (at one and not at both ends, since the screen provides protection from radio interference!).
The most effective way is to disconnect one of the devices (for example, a laptop) from the common ground circuit through the power supply network (using an adapter from a three-contact plug to a two-contact plug, or use an extension cord without grounding) using an adapter. But you should not do this for all devices at the same time, as in this case, the “floating potential of the earth”, which is life-threatening, may appear on the body of the equipment.
Source: https://habr.com/ru/post/131744/
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