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Старый 16.04.2011, 17:32   #26
Igodor
 
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Регистрация: 15.03.2009
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А вот какие будут мнения у форумчан по поводу одного из изобретений Яна Мейера - применяемой им в своих усилителях Active balanced headphone ground ?

http://www.meier-audio.homepage.t-on...e/symphony.htm
Цитата:
Active balanced headphone ground


Each driver of a headphone is connected to the amplifier by two wires. Normally one of these wires (the ground wire) is connected to ground and thus carries a constant zero-Volts signal. The other wire carries a varying voltage, the electrical audio signal. The driver is driven by the voltage-difference between both wires.

The voltages of the 4 wires change continuously and the external electrical fields generated by the electrical charges on the wires change accordingly. There is energy associated with these fields and thus energy is constantly stored and released. The properties of the insulating material have a strong influence on this process and thus effect sound quality.

The SYMPHONY does not keep the signal of the ground wires fixed but adds an extra signal to all the four wires (signal wires and ground wires) such that the sum of the voltages of the 4 wires is constantly zero. This extra signal is the same for all wires so the voltage differences between the two wires of a single driver do not change. The effective audio signal is still the same.
However, since the sum of the voltages is zero, the total electrical charge on the wires is also zero. The external potential field is strongly reduced and much less energy is stored and released when an audio signal is applied. The purity of the sound signal is much less effected by the properties of the insulating material.

The pictures below show an example of a typical headphone cable driven by a conventional headphone amplifier (left picture) and by the SYMPHONY (right picture).

At the left below we see the signals as generated by a conventional headphone amplifier. The ground signal is kept constant. Left and right channel signals vary independently.

At the right we can see the signals generated by the SYMPHONY. The ground wire now carries a signal that is also added to the left and right channel signals. The difference between Left and Ground and between Right and Ground is the same as in the left picture.

The left picture below shows the electrical potential field of the positively charged headphone cable when both signal wires carry a positive signal at the point of time indicated by the yellow bar at the picture above.
The right picture shows the potential field for balanced ground operation. It can be easily seen that field potentials are much lower than at the left picture.

The differences are even more pronounced in the far field, as shown in the next pictures. Since the "balanced" headphone cable has zero netto charge there is hardly any energy stored in the far field.

Apart from these principle benefits there are also some technical advantages offered by active balanced headphone ground.

When a positive signal is applied to a headphone driver by a conventional headphone amplifier current passes from the output stage of the amp, through the headphone driver towards the ground plane of the amp. During this process the current is "taken" from the positive power supply line whose voltage, as a result, will not be entirely constant. (In the pictures below the positive and negative supply lines are depicted as two large storage capacitors.)

The currents that run through the ground plane do induce small voltage differences. Ground is thus polluted and since it acts as a internal reference for all signal amplification processes sound quality is impaired.

Also variations of the powersupply lines are not entirely rejected/neglected by the output stage and are partly transferred to the output signal. This reduces sound quality even further.

When a signal is applied by the SYMPHONY, current passes the signal output stage, the driver, and the ground output stage. Both positive and negative powersupply lines are "loaded" simultaneously. No driving currents pass through the internal ground plane. There is no pollution of the internal referfence.

The voltage variations of the two powerlines are mirrored. Their mean value is roughly constant. This strongly increases their rejection at the output stages.

If voltage variations are found in one of the powerlines only, then these have a similar effect on the signals of both the signal output stage and of the ground output stage. However, it is the difference between the two output signals that drives the headphone. This difference is not changed and the effective audio signal is not influenced. PSRR (Power Supply Rejection Ratio) is very high.

Balanced ground thus offers many advantages for a faithfull reproduction of your favourite music. It certainly makes the SYMPHONY to one of the best amplifiers currently available.
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