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The requirements of a power supply for flawless audio reproduction are straightforward
but important. The supplies in the FET PREAMPLIFIER 02b take a very direct approach to
high performance. First, a top quality shielded toroid transformer with plenty of reserve
current capability is used. About 28,000 uF of capacitance with very low ESR and
inductance provides good passive filtering. A reference voltage is developed by
delivering a constant current to zener diodes. The resulting voltage is heavily filtered and
delivered to each stage through independent class A followers which completely
decouples the stages. The resulting non-reactive low impedance over an extremely
wide bandwidth yields a perfect power source for the individual circuits. The simplicity
and absolute stability of the supplies removes the chance of unpredictable interactions
which may occur with the more elaborate, high feedback circuity often used.
Most companies in the upper end of the audio industry use either sheet metal or
formed aluminum. By contrast, the FET PREAMPLIFIER 02b has all structural parts made of
machined extruded aluminum. The advantage of this over an all stamped chassis is that
the machined metal can be worked more precisely allowing us to work on tighter
tolerances and use PC mounted parts more easily. Moreover such a design allows easier
servicing either for repair or for future upgrading. From the standpoint of appearance,
a machined surface can be contoured in a far more precise manner, giving the final
product a more seamless appearance.
DESIGN PHILOSOPHY 8