Mains pollution can severely degrade the
sound reproduction of your audio system
Mains noise and sound quality
Many audio enthusiasts who own a high-end audio system are constantly looking for ways to improve the sound quality. This search includes for example, experimenting with other cables, feet or audio components. Insufficient attention is often paid to the impact of noise on the mains and the earth, while there is a lot to be gained here. Noise on the mains and protective earth almost never manifests itself in obvious ways, such as hum or other audible noise, but rather hides itself in the background. This results for example in haze, too much sharpness, limitation of dynamics, loss of musical details or reduction of spatiality. Usually it is a combination of these unwanted effects.
Power grid architecture
In western Europe, most of the electrical energy is produced in power plants. This energy is first transformed to a high voltage to reduce the loss of power during long distance transport. A common voltage is 380kVAC. Using transformers, this voltage is gradually reduced to the 230VAC that is provided through the wall outlets.​
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â–ºIndicative power grid architecure
Because all electricity users from different countries are connected to the same grid, they are interconnected. This means that if one user causes noise on the grid, other users can experience problems from it.
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The 230VAC wall socket contains three conductors: Live, Neutral and Earth. The Live and Neutral conductor provide the necessary energy to the connected appliance. The Earth conductor is used for human safety in fault condition, called Safety Earth, and as protection of the connected appliances, called Protective Earth. But this earth conductor is also used as the absolute reference in your audio system.
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â–ºCommon protective earth source
​The earth wire (or protective earth) is implemented in various ways. In most cases, the earth wire is supplied as a separate conductor by the energy provider. However, there are also implementations where earthing is achieved with a locally installed earth rod or a connection to the water supply network. In all cases, the earth wire is connected to the neutral conductor at a certain point. The location where this connection is made varies by country and the age of the fusebox, as regulations change over the years. In recent installations, an earth rod (or ground rod) has been driven at the last transformer station where the voltage is converted to 230 VAC for distribution to end-users. The protective earth offered to end-users is connected to this earth rod.
Noise on the Power grid
Most electrical appliances generate noise due to the way the electrical energy is used, for instance:
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Constant changing load, like dishwashers, tumble dryers and washing machines.
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RF noise by switched power supplies, like TV’s, cell phone chargers and computers.
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Devices that use only a part of the sine-wave, like dimmers and conventional power supplies.
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Devices with motors that use brushes.
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Switched power supplies from solar panels that feed back into the grid.
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â–ºIdeal vs actual mains voltage
All types of mains disturbances can be reduced to two types of noise:
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Noise across Live and Neutral, with equal amplitude but in opposite phase. So relative to the Protective Earth they cancel themselves out. This is called Differential Mode Noise.
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Noise that exists on both the Live and Neutral, equal in phase and amplitude, relative to the Protective Earth. This is called Common Mode Noise.
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â–ºDifferential Mode Mains Noise
â–ºCommon Mode Mains Noise
Common mode noise is not just about interference between phase and neutral with respect to the earth conductor. It can also arise directly from noise on the earth conductor itself. Although this noise can have a number of causes, mains filters often play an important role.
Mains filters are usually installed at the input of noisy equipment to prevent interference from flowing back into the mains. These filters use a combination of inductors and capacitors and, crucially, they use the earth conductor to dissipate some of this noise. This process, while beneficial to the mains, can unfortunately introduce common mode noise into your earth conductor.
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Impact of mains noise
The subtle ways mains noise and earth contamination affect audio quality are often overlooked, but their impact is significant. They rarely manifest as obvious hums or buzzing; instead, they subtly degrade your sound.
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To understand how mains noise impacts sound, we need to look at how electrical circuits within audio components process this unwanted interference.
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Differential mode noise typically has the least impact. This is because the 230VAC mains voltage itself is differential mode. A well-designed power supply is generally effective at converting most differential mode noise into clean, usable energy for the audio component
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However, common mode noise usually has a significant impact on sound quality. This common mode noise travels through both the phase and neutral conductors and is then dissipated through the ground conductor. This results in a current flowing through the earth wire. Since the impedance of the earth wire is not zero, this current creates a voltage on the earth wire at your audio components.
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The consequence of this is an elevated electrical noise floor within the audio components. This causes valuable musical details to fall below the noise floor, effectively losing them. The result is a loss of spatial information, diminished soundstage depth, and a hazier overall sound image. Other potential consequences include restricted dynamics, increased harshness, and further loss of musical nuances. It's usually a combination of these undesirable effects that degrades the listening experience.
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Noise reduction
Since you have virtually no control over the noise on the mains, it's highly beneficial to address this locally within your audio setup. The best approach is to tackle noise on both the mains and the protective earth.
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Reducing Noise on the Mains
Mains noise can be significantly reduced by adding a high-quality audiophile mains filter to your audio system. Various products are available, based on different concepts (such as filtering with chokes, filtering with an isolation transformer, or creating clean voltage with a regenerator). The effectiveness of these products varies and also depends on the audio system itself.
Reducing Noise on the Protective Earth
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Noise on the protective earth is not easy to reduce. The challenge here is that the earth serves as the absolute reference. There are concepts like Grounding Boxes that absorb high-frequency noise from the earth using minerals (the minerals resonate with the noise, converting part of it into heat, thus cleaning the earth). However, the most efficient method is to install a dedicated earth connection used only by the audio equipment. This allows the audio equipment to be decoupled from the safety earth, providing a clean audio earth. Please note: this can only be done if electrical safety remains guaranteed.