The RSA-M99 is a high-performance, highly efficient PWM class-D amplifier. It features power MOS-FETs that achieve highly accurate
current switching in the power stage, and high-voltage gate driver ICs with excellent time-axis control. The exceptional power
handling performance of the class-D device ensures dynamic real sound even when driving low-efficiency speakers. Furthermore,
the sweet and rich tonal character recalls the tone of the best triode tube amplifiers and enables ideal real sound experience.
Oil capacitors reproducing both tonal characteristics of vintage ampliers
and modern sound
The excellent PWM switching that makes it possible to maximize amplifier device potential, natural harmonics, and the dynamic
and rich sound on a wide spectrum owe a lot to the individual parts of the low-pass filter in the final stage of the amplifier. It
employs hermetically sealed paper-oil filled capacitors, a type that became fairly rare nowadays, made especially for the RSA-M99
by Arizona Capacitors, Inc. These capacitors produce a distinctive and superior sound that combines the deep tonal characteristics
of those old tube amplifiers with a modern vivid sound. Furthermore, coils are low-loss toroidal coils featuring special ring cores
that have been carefully chosen through listening tests to guarantee a natural sound with no distortion.
Outstanding power source that ensures high quality sound
In order to maximize the potential of the unprecedented high performance of this amplifier (power efficiency in the power stage
at maximum output of 96%), we daringly employed a classical and very simple plus/minus power source composed of a minimal
number of high quality components, such as only transformers, bridge-diodes and capacitors. The real sound of RSA-M99 has
been achieved thanks to instantaneous power supply function and to the high quality of power supply parts that could be
obtained only by paying the utmost attention to the audio characteristics of each individual part.
◇Power source capacitors
Multiple electrolytic capacitors with different audio characteristics are used in parallel to ensure a sufficient rectification capacity
while providing a well-balanced sound across the entire range. Furthermore, they ensure a smooth sound with an excellent rise
by improving the equivalent series resistance (ESR). In addition, high-voltage paper-oil filled capacitors are connected in parallel
to achieve a precise and beautiful sound over the mid to high ranges.
◇Rectifier
High-voltage and high-current newly-developed SiC (silicon carbide) Schottky diodes, designed to completely eliminate switching
noise, achieve not only transparent but also very powerful sound
◇R-core transformer
High-capacity R-core transformers are employed. Because the unnecessary leakage of magnetic flux is very low, responsiveness
to instantaneous high voltage is excellent, thereby realizing high speed sound with an excellent rise.
Thorough internal shielding for an electromagnetically clean space
High-frequency electromagnetic waves generated by the power source and other circuitries inside an audio device negatively
affect the sound. An electromagnetically cleaned environment is ensured inside the RSA-M99 by blocking the interaction between
circuitries using a special shield case made of steel sheets equipped on the power source transformer, the power amplifier part
and the low-pass filter. This thorough electromagnetic shielding makes the pure sound characteristic of the RSA-M99 possible.
Only high quality parts
High quality parts have been selected so the RSA-M99 can provide continued enjoyment over its long life. Parts necessary for
high quality sound were carefully selected and employed, including a high-capacity power switch with a locking mechanism,
industrial use selector and custom-made volume knob with excellent feel and high reliability, and RCA jacks with high-value
rhodium plating.
Chassis and insulators to reproduce natural resonance
Natural wood with beautiful resonance is used for the chassis and insulators. Solid laminated board of European spruce, known
as a tonewood, is used for the chassis in order to absorb undesirable vibrations of the mainframe. Insulation using a minimum
surface was made possible through round insulators made of painted maple, a strong wood from Hokkaido in Japan. In addition
to the stable 3-point support of the RSA-M99, it ensures no loss in the amplifier sound quality and full performance even when
mounted in an audio rack.
Power amp mode
The RSA-M99 is a preamplifier with an extremely simple structure composed of a selector and volume control. It can also be
used as a power amplifier by connecting it to a preamplifier or an AV amplifier. In this case, set the switch on the rear panel to
“POWER AMP” mode. The volume knob operation will be disabled and the gain will be fixed so that the volume control can be
operated only on the preamp or AV amplifier side.
