amplifier module
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amplifier module
The 250x3R consists of three identical power
amplifier modules in a single compact
enclosure. Each module is a complete, self-
contained amplifier, with its own power
transformer, bridge rectifier, energy storage
capacitors and amplification stage, requiring
only mains supply and control signals to
function.
Control signals are used to switch each
amplifier module individually on/off and to
protect it in case an error condition, such as
a short circuit in the loudspeaker, is detected.
Each module has its own high-efficiency
aluminium heatsink for excellent heat
dissipation, allowing it to drive even the
most critical loudspeakers safely and totally
independently from any of the other modules.
This results in uncompromised sound quality
with perfect channel separation.
Each 250x3R module delivers typically 255
Watts into 8 ohms, 400 Watts into 4 ohms
and will drive 1000 Watts into 2 ohms for
short durations.
As a result of the 250x3R‘s self-contained
amplifier module construction, this
performance is wholly independent of the
number of channels being driven and thus
even during the loudest passages of your
favourite movie the soundstage remains
stable, controlled and detailed.
There are many design features which have
been derived from our excellent 100x5R
and our F1-600MR amplifiers to make
this amplifier very special. We have listed
a few of these very technical items on
the following pages.
the traditional TO3, enhancing the amp-
lifier’s reliability for many years to come.
exceptionally accurate quiescent stability
It is universally accepted that accurate
setting and stability of quiescent conditions
is crucial to optimal Class-B amplifier
operation. The bias range over which the
best linearity is obtained is narrow, and on
either side of it crossover distortion
increases markedly. The 250x3R has one
of the most accurate quiescent controls ever
implemented, stabilising against output
level, load impedance and mains voltage
changes.
sophisticated muting
The 250x3R has a sophisticated muting
system, which stops you hearing loud,
annoying switching noises and protects
both the amplifier and the loudspeakers.
Particular care has been taken to make
sure that the muting circuitry, when
switched off, doesn’t affect the sound
quality. For this purpose carefully selected
relays with minimal crosstalk between coil
and contacts have been used.
an optimised mix of global and
local negative feed back
The 250x3R gives excellent linearity and low
distortion without relying on high global
negative feedback, which can present
difficulties when handling rapidly-changing
signals. The amplifier implements at each
amplifying stage a controlled amount of local
feedback, which not only linearises but also
defines the gain and other vital parameters
closely.
cascode compensation
The 250x3R uses an advanced stabilisation
concept called Cascode Compensation.
This might be the first time that this
sophisticated and elegant system has been
used in an audio amplifier. Its advantages
are excellent stability, inherently good
supply-rail rejection and a reduction in DC
drift. This gives outstanding stability with
performance drifts being virtually eliminated.
output transistors
The output devices are bipolar junction trans-
istors chosen for maximum linearity. The
advanced MT-200 package is used which
gives a greater area for heat transfer than
deep under the skin
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