Product Concept and Description
Back in 1986, Cello introduced the Performance Amplier which was designed to provide
the most natural sound and widest dynamic range from recordings. The new Cello
Encore amplier is the rst amplier to really sound like a Performance Amplier because
it uses the driver board from the original Performance, updated to modern parts and
assembled using traditional techniques.
Rated at 125w/ch @8ohms the stereo Cello Encore amplier comes in two chasses with
the amplier channels residing separately from the Cello Master power supply in exactly
the same way that the Cello Chorale preamplier is powered by the Cello Master.
The Cello Encore amplier from Matthew James incorporates a number of engineering
advances which allow high performance in a compact and ecient design, providing a
practical and appealing product for inclusion in music systems of the highest quality. The
circuitry is exceptionally stable and can be used with speakers which present loads as
low as 1ohm.
The Encore is designed to have the lowest possible levels of distortion while under actual
use, as opposed to simply measuring well on a test bench. The circuitry is designed
to perform well under the complex resistive, reactive and regenerative loading which
loudspeakers present to an amplier. The design approach has been to place importance
on the requirements of actual music reproduction. Many ampliers utilize some form of
soft-clip circuitry to deal with overload. The problem is that many of these approaches
introduce additional forms of distortion before the actual overload threshold is reached.
Furthermore, most designs to control overload are not comprehensive in dealing with
all of the situations that negatively aect an amplier’s ability to remain stable under
demanding situations. The Encore has been designed to control all forms of overload
under all conditions.
Considerable eort has been made to reduce low frequency errors, because most of
the energy in music and lm sound reproduction is present in this part of the frequency
spectrum. It is crucial to maintain low intermodulation distortion of low level, high
frequency information in the presence of large low- and mid-frequency signals under
complex loading. The Encore is designed to have the lowest distortion at small signal
levels and to gradually increase with signal level. While this results in slightly higher total
harmonic distortion (THD) measurements at full power levels, it conversely allows for the
lowest possible distortion under actual listening conditions. Again, the requirements for
accurate music reproduction have taken precedence in all design decisions.
The input stage of the Encore amplier remains under control under any overload
condition. The design tactics were chosen because they provide wide dynamic range
and provide a greater measure of resistance to overload than other possible choices.
