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BORN OF LISTENING
New Mark Levinson products are not introduced with
the seasons, or according to arbitrary marketing
schedules. They’re introduced as new technologies,
which have shown promise on paper, are perfected and
proven through rigorous in-house development and
evaluation procedures. In the case of the N
o
53, a highly
experienced evaluation team was assembled to conduct
blind and sighted listening tests of a novel switching
amplifier prototype, measuring it against past and
present Mark Levinson linear power amplifiers as
well as a range of competitive products.
As the development process wore on, power amplifiers
deemed sonically inferior were removed from further
testing. Several judges were surprised to learn that the
new switching amplifier was never among them. In
fact, the early N
o
53 prototype emerged as a winner,
with several panelists awarding it top honors for speed,
dynamics and clarity. It was, to say the least, an
unexpected result. For a mere prototype switching
amplifier to hold its own against linear amplifiers that
were deemed to be the very best the marketplace had to
offer – time-honored Mark Levinson models included –
meant we knew we were dealing with a
paradigm-shifting design.
Convinced that the minor quibbles that had come up
during the initial listening tests could be overcome, the
N
o
53 project was commissioned, and development of
the first new Mark Levinson Reference power amplifier
in more than a decade began in earnest.
THE TECHNICAL CHALLENGES
All power amplifier designs have inherent pros and cons
based on their design topology, and switching designs
are no exception. On the plus side, switching amplifiers
are more powerful, smaller and run cooler than their
linear counterparts – by several orders of magnitude. As
points of comparison, the Mark Levinson N
o
33 is rated
at 300 watts into 8 ohms, measures 31 x 14 x 31 inches
and weighs in at 435 pounds, while the N
o
53 – at 500
watts, 21 x 9 x 21 inches and 135 pounds – is nearly
twice as powerful, substantially more compact and 300
pounds lighter.
The N
o
53 is capable of generating truly phenomenal
power levels to support both the instantaneous and
continuous demands of virtually any speaker load. More
impressive, the N
o
53 accomplishes this feat while main-
taining a constant, thermally balanced operating temper-
ature. Although always warm to the touch, the operat-
ing temperature of the N
o
53 will not vary – or exhibit
even the slightest change in performance capability –
regardless of how long or hard the amplifier is driven.
The downside of switching power amplifiers? Because
they switch output devices on and off in very rapid
succession to mimic the input signal – one set of output
devices drives the positive half of the waveform, and a
separate set drives the negative half – switching noise
and dead bands become significant design challenges.
SWITCHING OFF SWITCHING NOISE
In most switching power amplifier designs, a brick-wall
filter is placed above the audio band to remove switch-
ing noise. But because of the filter’s physical proximity
to the audio band, this has a significant adverse effect
on phase relationships, the smoothness of frequency
response and imaging. In short, it degrades overall
sound quality. To overcome this challenge,
Mark Levinson engineers devised Interleaved Power
Technology (IPT), a patented method of raising the
amplifier’s switching frequency. In the case of the N
o
53,
the switching frequency is raised to an extremely high
N
o
53
REFERENCE POWER AMPLIFIER
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