Specifications

Page 9
Efficiency
Many modern amplifiers are extremely ineffi-
cient. Enormous amounts of their power, in fact
most of it, is wasted as heat.
Audiophiles who prefer to leave their amplifiers
on continually have discovered that a large,
inefficient power amplifier can add over $100
per month to their electric bill. In a ten-year
period, their amplifier will cost them $12,000 in
electricity! To produce so much waste heat,
some of these amplifiers even require special
mains wiring.
Roger Sanders believes that the use of such
amplifiers is absurd, unnecessary, and
environmentally irresponsible. Proponents of
these amplifiers claim that inefficiency is
necessary to keep distortion at very low levels.
At one time this may have been true. But with
modern technology, it is possible to make
amplifiers that are extremely efficient while still
maintaining vanishingly low distortion levels.
The ESL amplifier has less than 0.03% distortion
from 20 Hz to 20 kHz up to the onset of clipping.
It does this while dissipating only a few watts at
idle and actually runs cool to the touch. It may
be left on indefinitely without concern for
electricity usage.
Stability
The weird phase angles and high reactivity of
ESLs causes conventional amplifiers to become
unstable. The ESL amplifier solves this problem
by avoiding the use of global feedback, using
modest amounts of local feedback at the input
stage, and an output stage with so much capacity
that it is essentially unaffected by reactive loads.
The result is an amplifier that is completely
stable under all conditions — even at turn-on
where no muting circuit needed or used. There
is no “pop” or “thump” at either turn-on or turn-
off and the amplifier switches on instantly.
Size and Weight
Many of today's best amplifiers are so large and
heavy (over 100 pounds) that one person cannot
lift them. They cannot be placed on a shelf or in
an equipment rack. Some are so big that they are
split in two parts — a “mono-block” for each
channel. It often is difficult to find a place on the
floor to put them. Many spouses are less-than-
pleased about having such large amplifiers
cluttering their living space.
To produce large amounts of power for driving
resistive loads in highly inefficient amplifiers, it is
necessary to use outrageously large and heavy
power supplies and huge heat sinks. So it is not
surprising that such amplifiers are immense.
Despite its vast output potential, the ESL
amplifier weighs just 51 pounds and is sized
scarcely larger than a full-sized preamp. Its
dimensions are 17" wide x 5.5" tall x 16" deep.
Roger Sanders has achieved this remarkable
compactness by using a chassis made mostly of
lightweight machined aluminum, and using the
power supply to drive speakers instead of having
its power converted to waste heat.
Because the ESL amplifier generates so little
heat, the heat-sink requirements are greatly
reduced. Additionally, high-efficiency heat-sinks
are used that make it possible to further lessen
the weight and size of the amplifier. Nor is this
compactness achieved at the cost of having a
noisy cooling fan. The amplifier is completely
silent.
Due to its very low idle current, the amplifier can
and should be left on continually. There is no
need to turn it off and on, which stresses internal
components with voltage surges.
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