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BURMESTER 948 POWER CONDITIONER

The Power Conditioner 948 is one of our most innovative products. It is the result of our many years of basic research. For the method of power conditioning applied in the 948 we were awarded a world patent (No. 44 26 721). The power conditioner is one of our most successful designs with sales to prove it. It’s outstanding qualities are recognized internationally. The U.S. high end magazine the absolute sound classifi ed it as a four star component and wrote: „The 948 is incompara- ble and in a class by itself.“

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THE PROBLEM TO BE SOLVED

Increasing noise pollution in our power lines renders the AC voltage (nominal 230 volts,
50 Hertz) that comes out of our wall outlets one of the weakest links in the high end audio
chain. Who has not experienced the phenomenon that a music system doesn’t sound as
good between six and ten in the evening as it does at midnight? The reason: The power
that flows from the wall outlet at midnight is much cleaner than that of a few hours earlier.
What causes this effect? Burmester Audiosystems identified after some basic research a
noise component in the power supply that is solely responsible for the sound deterioration.
We measured a miniscule direct current of a few millivolts in the AC voltage. Not only
was this DC component not supposed to be there it also varied it’s strength over time. As
it increased the sound of the system got worse. Available line filters did nothing to deal
with this kind of line pollution. This is too bad because a few millivolts of DC are enough
to drive amp transformers of any brand to the saturation point which becomes audible as
transformer hum. As is widely known, the pure-bred transformers of high end-amplifiers
are particularly susceptible to DC components in the power supply.

SPECIAL FEATURES OF THE 948: PATENTED ACTIVE DC SUPPRESSION

The power conditioner 948 functions unlike any other line filter on the world market. Basically,
the 948 is a 500 W power amplifier that works in parallel with the AC power supply
and compensates as an active system any DC components in the 230 volts AC from the wall
outlet. Our patented circuit design does not limit the power to the audio system in any way
and, thus, allows very powerful amps, including several large mono amps to be hooked up
to the 948. With common passive filters this would only be possible at the price of deteriorating
sound. The active DC suppression works on all eight outlets of the 948 and it can
be switched on and off.

THE SECRET OF THE 948

The task of the power conditioner is, simply stated, to keep the average phase difference
of the AC power supply at zero. An average other than zero means that direct current is
present in the alternating current of the household power.

In the phase-plane diagram of the AC voltage the waveshape of the phase alternates
around the zero line of the neutral conductor. In an ideal AC power situation the area plotted
by the positive half-wave (A) above neutral equals that by the negative half-wave (B)
below it. Ideally, the mean value when adding positive and negative areas over time should
be zero, indicating that no DC voltage is present.

Unbalanced AC voltage:

There are many electrical loads that absorbe more power on one half, positive or negative,
of the wave cycle than on the other. This is particularely true for appliances with generalized
phase control which do not control the two half-waves identically, such as dimmers,
motor power controllers, computers, microwaves, TVs or hair dryers which control power
to the heating element by connecting a diode in series.
Even remote large loads such as heavy electrical equipment on a nearby construction site
strongly effect the quality of the AC voltage supply in the power system.
If a load absorbes more power from one half-wave than from the other the voltage drop in
the system is larger for the strained half of the wave cycle than for the other. Consequently,
the wall outlets of a power system under unbalanced loads will supply AC voltage with a
phase-plane diagram in which one half-wave is smaller than the other. In a simplified graph
it would look like this:

In an unbalanced AC voltage supply the area plotted by the positive half-wave is unequal
the area plotted by the negative half-wave. Their addition renders a value other than zero,
meaning the mean of the AC voltage is unequal zero, hence there is a DC component in
the power system.
Unbalanced AC voltage and transformers
A transformer hooked up to an unbalanced AC voltage is constantly carrying direct current.
This leads to a strong magnetic bias in its core, the transformer starts to hum. This problem
increases the lower the resistance in the windings and the higher the magnetic flux in
the core is. In other words, the more powerful and dynamic a transformer is designed the
more susceptible it is to DC components in the power system. In good transformers even
miniscule DC components of a few 10 mV are audible.

HOW THE POWER CONDITIONER 948 WORKS

The power conditioner 948 measures the mean value of the supply voltage and adjusts it
to zero by putting additional load onto the larger half-wave. In other words it assures that
the voltage drop in the system is identical for the positive and negative half of the wave
cycle. Hence, transformers no longer have to cope with direct current and stop humming.
It is important to note that the power conditioner works in parallel with the connected audio
components and thus avoids an undesirable damping of the voltage supply. This circuit
logic is unique on the world market and has been patented by Burmester Audiosystems.

AND HOW DOES IT SOUND?

A power supply corrected by the power conditioner provides the connected audio components
with clean and even voltage. The result is a totally open sound. There is more air
around voices and instruments, large orchestras and choirs sound natural and unstrained
– even at high volumes. The tonal balance of music becomes sweeter.
This improvement, of course, is independent of the time of day. With the 948 an audio
system sounds as good all day as it normally sounds only way past midnight, when no spurious
loads pollute the power system. We recommend visiting your authorized Burmester
dealer and trying a 948 out for several days. It will improve the sound of any brand of audio
equipment.
It’s outstanding sonic qualities have earned the 948 recognition worldwide. The absolute
sound awarded it four stars and wrote: „Incomparable and in a class by itself..“. Many editors
of audio magazines around the world use the 948 as an important tool.

WHAT DO OTHER POWER CONDITIONERS DO?

Many competing products try to keep line noise away from high end audio systems by stabilizing
the voltage or synthesizing the supply system. However, this can easily compound
the problem by destroying the low resistance of the voltage supply. Only a low-resistance
system can supply large amounts of power in the shortest time. Higher resistance limits the
overall power of the connected components. This leads to a limp bass reproduction, for
example.
The 948 avoids this danger altogether by functioning in parallel to the supply system, meaning
that the power does not flow through the power conditioning section. The 948 does
not work in series with the connected audio components, it effects the voltage supply from
the outside, so to speak, without impeding or limiting it.
The 948 is not designed to stabilize the voltage supply, which would make little sense
anyway because most high end components have their own voltage stabilizers. Common
power filters based on the isolating transformer principle oftentimes only limit parasytic RF
noise above 100 kHz. Also, they work in series with the connected components and limit
the power flow, thus, are not usable for power amplifiers.
The two RF line filters of the 948 kick in at very low frequencies (-6dB at 2000 Hz).

AND HOW DOES IT SOUND?

A power supply corrected by the power conditioner provides the connected audio components
with clean and even voltage. The result is a totally open sound. There is more air
around voices and instruments, large orchestras and choirs sound natural and unstrained
– even at high volumes. The tonal balance of music becomes sweeter.
This improvement, of course, is independent of the time of day. With the 948 an audio
system sounds as good all day as it normally sounds only way past midnight, when no spurious
loads pollute the power system. We recommend visiting your authorized Burmester
dealer and trying a 948 out for several days. It will improve the sound of any brand of audio
equipment.
It’s outstanding sonic qualities have earned the 948 recognition worldwide. The absolute
sound awarded it four stars and wrote: „Incomparable and in a class by itself..“. Many editors
of audio magazines around the world use the 948 as an important tool.

WHAT DO OTHER POWER CONDITIONERS DO?

Many competing products try to keep line noise away from high end audio systems by stabilizing
the voltage or synthesizing the supply system. However, this can easily compound
the problem by destroying the low resistance of the voltage supply. Only a low-resistance
system can supply large amounts of power in the shortest time. Higher resistance limits the
overall power of the connected components. This leads to a limp bass reproduction, for
example.
The 948 avoids this danger altogether by functioning in parallel to the supply system, meaning
that the power does not flow through the power conditioning section. The 948 does
not work in series with the connected audio components, it effects the voltage supply from
the outside, so to speak, without impeding or limiting it.
The 948 is not designed to stabilize the voltage supply, which would make little sense
anyway because most high end components have their own voltage stabilizers. Common
power filters based on the isolating transformer principle oftentimes only limit parasytic RF
noise above 100 kHz. Also, they work in series with the connected components and limit
the power flow, thus, are not usable for power amplifiers.
The two RF line filters of the 948 kick in at very low frequencies (-6dB at 2000 Hz).

 

» Tekniske data

Dimensions (WxHxD): 485mm x 155mm x 365mm
Weight: app. 18kg (depending on model)

SPECIAL CHARACTERISTICS
Completely certified by VDE and TÜV, conforms to CE guidelines. The 948 conforms to all
electrical safety standards (separatly grounded inner housing)
Electrically and magnetically triple-shielded Burmester Power 2.5 power cord of 2 m length
is the standard AC cord. Longer power cords optional.
We recommend using triple-shielded Burmester Power 2.5 power cord also for all other
connected components to avoid polluting your just cleaned voltage supply with RF noise.
Power outlets can be custom configured as switched/unswitched and filtered/unfiltered.
Please specify your configuration when ordering the 948. For details, please contact your
Burmester dealer.

CONNECTIONS
Eight power outlets
Absolutely no power limitation for components connected to the outlets without RF filtering.
10 volts DC-Input for remote switching by Burmester preamps
Electrically and magnetically triple-shielded Burmester Power 2.5 AC cord as standard power
connection (2m length).

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