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This amplifier runs hot. The heat sinks will warm up in about an hour to a temperature which
will not be comfortable to touch for more than a moment or two, which is 120 to 130 degrees
Fahrenheit (50 to 55 degrees Celsius). This is normal, and there is a thermal shut off system
which will shut down the amplifier at internal temperatures in excess of 160 deg. F. and 70
deg. C. If the over temperature protection system is activated, it will shut down the amplifier
until the thermal sensor has cooled.
It takes at least an hour of warm up time to get the best performance out of the amplifier. It
will take that long to reach operating temperature and exhibit lowest DC offset voltage at the
output. However, prior to warm up, the amplifier will meet objective performance
specifications except DC offset voltage.
The amplifier does not require any maintenance. While the design is conservative, this is a
hard running amplifier, as single ended Class A operation is the least efficient operating
mode. In fifteen years the electrolytic power supply capacitors will get old. Depending on
usage, you will begin to have semiconductor and other failures between 10 and 50 years after
date of manufacture. Later, the sun will cool to a white dwarf, and after that the universe will
experience heat death.
Product Philosophy and Design Theory
When I started designing amplifiers 25 years ago, solid state amplifiers had just achieved a
firm grasp on the market. Power and harmonic distortion numbers were king, and the largest
audio magazine said that amplifiers with the same specs sounded the same.
We have heard Triodes, Pentodes, Bipolar, VFET, Mosfet, TFET valves, IGBT, Hybrids, THD
distortion, IM distortion, TIM distortion, phase distortion, quantization, feedback, nested
feedback, no feedback, feed forward, Stasis, harmonic time alignment, high slew, Class AB,
Class A, Pure Class A, Class AA, Class A/AB, Class D, Class H, Constant bias, dynamic bias,
optical bias, Real Life Bias, Sustained Plateau Bias, big supplies, smart supplies, regulated
supplies, separate supplies, switching supplies, dynamic headroom, high current, balanced
inputs and balanced outputs.
Apart from digitally recorded source material, things have not changed very much in twenty
five years. Solid state amplifiers still dominate the market, the largest audio magazine still
doesn't hear the difference, and many audiophiles are still hanging on to their tubes. Leaving
aside the examples of marketing hype, we have a large number of attempts to improve the
sound of amplifiers, each attempting to address a hypothesized flaw in the performance.
Audiophiles have voted on the various designs with their pocketbooks, and products go down
in history as classics or are forgotten. The used market speaks eloquently: Marantz 9's
command a high price, while Dyna 120's are largely unwanted.
There has been a failure in the attempt to use specifications to characterize the subtleties of
sonic performance. Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.
Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest
THD, or the highest slew rate, or the lowest noise, has not become a classic or even been
more than a modest success.
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