Absorb in ground noise like a vacuum cleaner

That was a few years ago. I put in a new little integrated amp, and as I stroked the chassis, a tiny electric current flowed through it. The strange thing is that if you hold the other terminal of the inter-cable connected to the amplifier with your hand, this electricity disappears. In the end, I decided that my body was acting as a kind of grounding wire, so I came up with a temporary trick (?). One wire of the unused speaker cable is connected to the amplifier (toggle switch on the front) and the other wire is connected to the ground pin of the multi-tap. It was not good looking, but the residual electricity in the chassis, which had a bad feeling, disappeared.

One of the problems we always encounter in our audio life is this kind of ground noise. Ground noise includes the chassis residual current noise mentioned above, power harmonic noise that makes the transformer tremble in severe cases, and hum noise generated from speaker woofers. . When these noises are reduced, the notes are clear, the background is quiet, and the bass is audible. I've experienced several cases where the soundstage was properly captured.

Ground vs Noise

Grounding protects people, devices, and music signals by letting all the large current flowing in 220V escape to 0V Ground/Earth. When you open the wall outlet, almost all of them have a grounding wire, and when you open an audio cable, almost all of them have a grounding wire. Chassis grounding is when the chassis of an audio device, which is a conductor component, is used as a grounding point. But there are two problems. First, these ground wires or chassis ground have 'Ground Inductance', which is a grounding disturbance component, so they cannot perform 100% of the grounding role.

Ground Loop

Second, there is a potential difference due to the different grounding performance of each device, and because of this, a portion of the large current that needs to escape to the wall outlet ground wire remains and circulates between the devices (Ground Loop). Ground loops are even more problematic in that they introduce power-supply harmonics. Power harmonic noise literally means that the harmonic harmonics (120Hz, 180Hz, 240Hz…) of the AC 60Hz frequency act as noise. Occurs.
Residual 120Hz is 'Hum' that the human ear can hear .

Therefore, in order to achieve perfect grounding, three measures must be taken.

First, it creates an environment closest to the 0V ground point. In other words, by connecting an artificial grounding box, ground noise, power harmonic noise, and chassis residual noise are directed there. Most of the grounding boxes put iron ore or minerals in them so that the grounding box serves as the most ideal land.

Second, the impedance of the ground wire is extremely low. Ground-related noise unconditionally gathers toward the low impedance side. The reason why the final destination of the ground is the ground is because the impedance of the ground is zero. Some cable manufacturers have introduced so-called add-on intercables with their low-impedance cables to replace the grounding wires of existing intercables.

Third, the ground is brought together to eliminate ground loops. In this way, the final potential difference becomes zero (0), so that a ground loop does not occur. This is the 'Star Ground' spoken of in the United States. It is called 'Star Ground' because the shape of five devices connected by one grounding point resembles a 'star'.

BOP Quantum Ground

Recently, I came across BOP Quantum Ground in the hi-fi club viewing room. This is the 2nd installment of the BOP Quantum series following the BOP Quantum Field, which was released and sold through the Hi-Fi Club last year. I am very happy for the author, who tested the quantum field at home for almost a month and was surprised by the dramatic sound quality improvement effect.

First, look at the exterior. The aluminum chassis front panel has a power indicator LED on the left and a toggle switch for mode selection on the right. There are two modes, high impedance and low impedance, which will be mentioned later. At the rear, an AC power inlet terminal and six ground terminals are provided. Unlike the quantum field, which was supplied with DC power through an adapter, the fact that the quantum ground receives AC power directly draws attention.

According to the manufacturer's current system and Hi-Fi Club, which participated in product tuning, Quantum Ground has a linear power supply and a lithium-ion battery inside to implement a constant voltage and ultra-low impedance circuit. In my view, quantum ground acts as a 'ground' that sucks in AC ground noise by maintaining a DC voltage with this very little voltage fluctuation and very low impedance.

In other words, unlike some manufacturers who put iron ore and minerals in the ground box to maintain 0V (passive), quantum ground is an active ground box through which DC voltage of extremely low impedance flows. 0V is ideal as a grounding environment, but if there is no voltage fluctuation and a DC battery with low impedance, it can act as a kind of reference point in terms of AC grounding noise.


Moreover, the manufacturer, Hyeon System, introduced the BOP L5 power supply using a lithium-ion battery a few years ago, so it is a manufacturer with a good knowledge of constant voltage and ultra-low impedance DC power. Anyway, for quantum ground, two of the 'three measures for perfect grounding' I mentioned earlier were satisfied. That is, 'to create an environment closest to the 0V grounding point' and 'to reduce the impedance of the ground wire extremely low'. And the mode selection of the quantum ground is nothing but a device that adjusts the amount of this ground impedance. According to the manufacturer, the mode selection is valid in this case.

  • High Impedance (toggle switch up): when using a transistor amplifier. It gives off a rich and natural sound.
  • Low impedance (toggle switch down): when using a tube amp. Transient characteristics are improved.

There is no specific explanation from the manufacturer in this regard, but in my view, this mode selection is a concept of relatively increasing or decreasing the impedance of the built-in DC battery circuit. Of course, the lower the impedance, the greater the grounding effect. Therefore, I would like to understand 'high impedance' as a kind of normal button and 'low impedance' as a turbo button.

Then, how was the last item of 'collecting the ground in one place to eliminate the ground loop' among the '3 measures for perfect grounding' implemented in quantum ground? This is done in two ways.

  1. Insert the AC plug of the quantum ground into the multi-tap to which the audio device's power cable is connected.
  2. Connect up to 6 grounding cables (4 spades, 1 RCA, 1 XLR) connected to each device to the quantum grounding terminal. In a word, it created a star ground environment.

The sonic gain that can be achieved through quantum ground

Then let's go back to the basics. What is the sonic gain that can be achieved through the active ground box, quantum ground? In summary, electrical harmonic noise cancellation, ground loop noise cancellation, chassis residual noise cancellation, etc.

electric harmonics

First of all, it is the effect of removing electric harmonic noise. Electric harmonic noise usually starts at 60Hz and goes up to 3,000Hz, which is the 30th harmonic, and above 3,000Hz is called high frequency. Therefore, if the grounding is done properly, the 60Hz~3kHz sound part will be clear, and if the electromagnetic noise is properly blocked, the 3kHz~20kHz harmonic part will come to life.

Moreover, since the energy of sound heard by the human ear is felt more in the mid-low range, the effect of removing the noise from 60Hz to 3kHz is inevitably more numerous. In addition, 60Hz~3kHz is a 'mid-low range' band in which the frequencies emitted by almost all instruments and vocalists of the orchestra are concentrated.

In my view, Quantum Ground (C) is surgery or chemotherapy that cuts out and kills cancer cells, and Quantum Field (Overtone) is like a medicine that gives vitality to the body.

[Ultra-low range] 20Hz to 60Hz

  • Pipe organ 16Hz~7kHz, piano 28Hz~4kHz (overtone 8kHz), double bass 41Hz~330Hz (overtone 5kHz), tuba 41Hz~349Hz (overtone 2kHz)

[Low Pass] 60Hz~250Hz

  • Cello 65Hz to 998Hz (overtone 6.5kHz), timpani 73Hz to 262Hz (overtone 3kHz), acoustic guitar 82Hz to 1.4kHz (overtone 5kHz), trombone 82Hz to 349Hz (overtone 7.5kHz), baritone 87Hz to 349Hz, viola 131Hz to 1.2kHz (overtone is 6.5kHz), tenor 131Hz to 523Hz, alto saxophone 147Hz to 880Hz, trumpet 165Hz to 988Hz, clarinet 165Hz to 1.5kHz, violin 196Hz to 3.1kHz (overtone is 10kHz), mezzo-soprano 220Hz to 888Hz

[Low mid range] 250Hz~500Hz

  • Flute 261Hz to 2kHz (overtones are 8kHz), soprano 261Hz to 1kHz, timpani highest 261Hz, double bass 330Hz, baritone highest 349Hz, trombone 349Hz, tuba 349Hz

[Midrange] 500Hz~2kHz

  • Piccolo 523Hz~4kHz (overtone is 14kHz), tenor highest 523Hz, alto saxophone highest 880Hz, mezzo-soprano highest 888Hz, trumpet 988Hz, cello highest 998Hz, soprano highest 1kHz, viola highest 1.2kHz, acoustic guitar Top 1.4 kHz, clarinet top 1.5 kHz, flute top 2 kHz

[High midrange] 2kHz to 4kHz

  • Violin highest note 3.1kHz, Piccolo highest note 4kHz

Therefore, the electric harmonics penetrate into the central region of all these notes, making the notes cloudy and reducing the focus. This is because the sense of localization is also stereo location information embedded in these frequencies. The following is the effect of removing ground loop noise. A ground loop is a noise in which electric harmonic noise circulates between devices like a soul wandering around the world due to the potential difference of each audio device. Quantum ground absorbs all of this ground loop noise through the star ground method. Therefore, the performance of the source device, the preamplifier, the power amp, and the integrated amp that contains all of these in one chassis is bound to skyrocket.

  • Source equipment: resolution, sense of stage, sense of space, SN ratio
  • Preamplifier: stage, space, sound vitality, SN ratio, power amp driving force
  • Power Amplifier: Imaging, sound energy, SN ratio, speaker driving force
  • Integrated amplifier: resolution, sense of stage, sense of space, vitality and energy of sound, imaging, SN ratio, speaker driving power


MSB's Premier DAC, Vitus Audio's preamplifier SL-103 and monoblock power amplifier SM-103, and Avant-Garde's Trio 26 LE speakers were used for the BOP Quantum Ground review held in the hi-fi club's main viewing room. As for the sound source, I mainly listened to the Kobooz streaming sound source through Rune. The settings were as follows. I plugged all the power cables into one multi-tap. DAC, preamplifier, 2 power amps, quantum field, there are 5 of them. And the quantum garround, DAC, preamplifier, and two power amps were connected with a grounding cable. The test was conducted in three steps: 1) without quantum ground, 2) with quantum ground, and 3) with addition of quantum field. For reference, the QF cable is already wound around the power cables of 4 devices for quantum field connection.

Salena Jones - You Don’t Bring Me Flowers
Best Audiophile Vocals IV

When the quantum ground is added, the position of the contra bass is definitely lowered and the vocals are relatively raised. It is only then that there is a difference in pitch between the instrument and the vocal.

If you look at the notes themselves, the contrabass sounds clear and clear. In this state, adding a quantum field opens up the space above the vocals. The bass of the contrabass also sounds like a wild horse tamed. When I listened to this in reverse order, the stage is narrow and negative numbers are reduced in the final pure state (quantum ground and quantum field not input).

Dave Brubeck Quartet - Take Five
Time Out

Is it because of the learning effect on the quantum ground? Even if you listen to it in its pure state for the first time, you will notice a lot of dissatisfaction. The whole stage is cluttered and the high notes are shot. When the quantum ground is put in, the stage suddenly becomes neat and the saxophone can be heard better. In particular, the stereo image and inter-instrument layer stand out.

1) The potential difference between the two monoblock power amplifiers is reduced by inputting the quantum ground, 2) the sound image produced by each of the two speakers becomes more accurate as a result, and 3) as a result, a stereo image is formed precisely. This seems to be the reason why the chorus part became more prominent after the introduction of Quantum Ground while it was completely turned off in Billie Eilish's 'Bad Guy'. Based on these first impressions, the role of quantum ground and quantum field is as follows.

  • Quantum Ground = Removes distortion components of the reproduced sound. Reduce noise. It separates the orchestra from the chorus. It also has a positive effect on the soundstage.
  • Quantum Field = Brings out overtones. Reveal what was buried The tone of the instrument comes alive.

Bill Evans Trio - Autumn Leaves
Portrait in Jazz

First of all, if you listen to it in its pure state, the bass is on the right, and the drum is on the high left. The bass sound is also good. But if you pay more attention, the piano notes dominate almost everything. It stands out too much. Then, when the quantum ground is put in, the bass definitely comes to life, and the three instruments are finally in balance. right. Quantum ground eliminates the power harmonic noise that gnawed at the base of the bass as an instrument.

When the quantum field is added, the sustain of the high notes of the piano progresses longer. Overall, the tones have changed in a delicious way. If you take out the quantum ground in this state, just in case, the power of the hand that rips the bass string is weakened. SN ratio also fell.

Eric Clapton - Wonderful Tonight
24 Nights

Even if I listen to it in a pure state, I wonder if the depth of the stage can be deeper than this. However, I am concerned that the chime is not very shiny, and that the overall tone is a bit muddy. When the quantum ground is put in, the cheers of the audience can be heard better. This is evidence that the SN ratio of the reproduced sound has increased. The guitar sounds fleshy and the chime is more audible. The sound is lively and lively. The electric guitar became more expressive, and Eric Clapton's voice became more liquid. By adding a quantum field with more greed (?),
the sense of space is increased and the drum cymbal sound is greatly emphasized. It feels more like being at a concert site.

Jack Johnson - Staple It Together
In Between Dreams

When the quantum ground is inserted, the center of gravity of the notes goes down and the high notes are shot less. Overall, the impression that the band is well balanced. The electric bass sound has also become more solid. It would be surprising if the tempo of the song improved as well. When I put the quantum field in, the high-pitched sound is completely revived to the point where I shouted 'Wow~~'. If the quantum ground is removed, the treble information seems to be the same, but the stage becomes distracting and the SN ratio deteriorates. When the quantum ground is applied again, the background becomes quiet, and each note becomes clear and moist. The body of the instrument is also revived. If we subtract both quantum ground and quantum field again, the drum cymbal sounds like a mechanical sound. The sibilance of the vocals was also prominent.

Andris Nelsons, Boston Symphony Orchestra
Shostakovich Symphony No.5
Shostakovich Under Stalin’s Shadow

When the quantum ground is inserted, the timpani sound in the beginning of the 4th movement is heard much louder and the front of the stage becomes transparent. The impression that all of this has to do with the SN ratio.

The presence of the wind part of the orchestra comes to life. When the quantum field is added, the notes become richer as if the number of orchestral instruments increased.

general review

When reviewing audio accessories, the most noticeable difference with and without was related to grounding. Overall, the noise is lowered, the notes are smoother, and the dynamic range is widened. The fact that the playback sound is vivid as if you were listening to it in the field, and that the stage is brighter than usual is a notable change. This was similar when listening to an intercable with good grounding measures.

Quantum Ground reviewed this time was no exception. When the quantum ground was put in, the bass became hard, the outlines of the notes became clear, and the stage became more three-dimensional. That is proof that power harmonic noise and ground loop noise are fully saturated among audio devices. I haven't tested it myself, but if the target device is a popular streaming integrated amplifier, the quantum ground effect is expected to be more pronounced. Serious listening is recommended.

by Kim Pyeon Audio Columnist