956 MK2 Power Amplifier

The Burmester stereo power amplifi er 956 MK 2 is a proud descendent of our internationally highly acclaimed family of power amps 911 and 909. Our reference amp 909 has
marked the pinnacle of audio amplifi cation since 1990. Many of the insights gained in
designing the 909 have infl uenced the concept of the 956 MK 2. Like our legendary preamplifi er 808 the 956 MK 2 is of modular design with the advantage that older models
can easily be upgraded to the latest version.

Like all amplifi ers from Burmester the 956 MK 2 is, of course, completely balanced and
DC-coupled without any distorting capacitors in the signal path. Also, the 956 MK 2 sports
the same cool-looking heat sinks which Dieter Burmester designed for his bigger amps.

The 956 MK 2 like all our amplifiers is a stereo amp. However, all Burmester stereo amps
can easily be bridged into mono operation using external mono adapters. If two amps are
ordered as a mono pair we will bridge the amps internally at the factory free of charge.
The rise time (the quickness of the amp) is the same whether it operates in stereo or mono
mode.
Furthermore, we offer bi-amping adapters for using a pair of 956 MK 2 with speakers that
require bi-amping.

All our amplifiers are run through a long battery of tests to make sure each one conforms
to our reference prototype. After the first computer-aided set of about 300 test measurements the units are burnt-in at nominal load for a week. After that we run a second set of
the same computer-aided tests. Only when the two results are identical will a unit be released for a listening test. If this final test meets our standards the unit will be packed and
shipped. By this arduous process of testing and re-testing we want to make sure that each
956 MK 2 fulfills our guarantee of reliability and musicality to our customers.

THE CONCEPT
The 956 MK 2 offers balanced circuitry and it is entirely DC-coupled. There are no distorting
capacitors in the signal path. An intelligent protection circuit outside the signal path monitors during operation for overheating, DC offset and overloading.

A special feature of the 956 MK 2 is its extremely high damping factor. This high damping
factor coupled with the ability to quickly deliver large amounts of current (rise time at 4Ω
is only 1.5 μS) enable the amp to effortlessly drive virtually any loudspeaker over it’s wide
frequency response. With its mighty power supply the 956 MK 2 is able to deliver high
currents continuously and thus easily control speakers with low impedance values and
complex loads. The frequency response is practically load-independent. Very good spacial
resolution, natural musical warmth and negligible distortion characterize the sound of the
956 MK 2.

The transistors of the output stages are placed on the oversized heat sinks that form the sides of the housing. The driver stages, however, are located on a separate internal heat sink.
This keeps the wide temperature fluctuations of the heat sinks from shifting the working
points of the amplification section.

Internal wiring of the 956 MK2’s inputs is done with 10 mm² high-purity copper cable. This
ensures that the high currents of the power amplifier reach the massive bindings posts without loss. With respect to signal-carrying conductors we conciously omitted copper rails
- which have become all the rage these days – to avoid unwanted microphonic effects.
For the internal connections that carry music signals we use our electrically and magnetically shielded “Burmester SILVER” cable.

THE SOUND
The 956 MK 2 is widely acclaimed for its naturally warm musicality and detailed imaging.
In its capability to unlock the smallest sonic detail in the world’s best speakers even at very
high volumes the 956 MK 2 is second to none.

UPGRADES
The new MK 2-version differs from its predecessor mainly by an expanded Class-A operation. Consequently, it gets noticeably warmer. For this upgrade the driver stages on the
interior heat sink are changed and the whole amp is completely re-tuned. The new driver
stages exhibit a considerably more linear power supply than their predecessors. This clearly improves the sound and lowers harmonic distortion. Additional holes have to be drilled
into the bottom of the housing for sufficient airflow to cool these drivers located on the
internal heat sinks. In comparison with the MK 1-version the power supply has been re-designed and the resistance lowered further. This is made apparent by the 3mm thick copper
rails fixed to the power supply board. These rails connect the large electrolytic capacitors
and serve as mass. The result of this extra material expense is a considerably lower internal
impedance of the power supply than the 75 μm thick copper on the circuit board.
For internal signal leads we changed the cables to “Burmester SILVER”.

The most obvious discriminating feature of the MK 2-version are it’s silver anodized housing
walls and heat sinks like those of the latest incarnations of the 911 MK 3 and the 909. All 956
MK 1 can be upgraded to a MK 2-version including a new two year warranty. However, the
upgrade does not change the housing finish.

TECHNICAL DATA

Dimensions (WxHxD): 482 mm x 191 mm x 482 mm
Weight: app. 30 kg (66lbs.)
Rated power output: Stereo: 2x240 W at 4Ω
Mono: 1x500 W at 4Ω
Continuous peak current: 34 A
Damping factor: >2000
Signal-to-noise ratio: >81 dB
Input sensitivity: 730 mV for full volume
320 mV for 100W at 4 Ω load
Frequency response: 0-200kHz (-3dB)
4 selected power transistors per channel
Rise time (stereo/mono): 1,4 μs at 4/8 Ω load
1,9 μs at 1 Ω load
Oversized power supply with 188.000 μF filter capacity and 600 VA toroidal transformer.
Additional local filtering close to the output stages of 12.000 μF per channel.