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In a switch mode power supply the incoming mains is filtered then rectified
to generate a very high voltage dc (direct current) supply. This is usually
about 300 to 350 Volts dc, which is far too high to operate audio circuitry
directly, and is still connected directly to the incoming mains supply. Such
a high voltage is very dangerous and is one reason why the Klimax case should
never be opened by a customer or a non Linn Products employee.
This high voltage is chopped up by very fast semiconductor switches and
applied to a small transformer which both transforms the voltage to the
value needed by the electronic circuitry and provides a safety isolation barrier
from the mains supply. The size of a transformer reduces as its operating
frequency increases, so a transformer operating at say 60,000 cycles per
second is far smaller than one operating at mains frequency of 50 or 60
cycles per second.
On the output of the transformer, very fast rectifiers, a small coil and small
capacitors filter and convert the high frequency waveform back to dc, ready
for the electronic circuitry to use. By controlling the timing of the switches
the output voltage can be held constant or varied, as required, without the
need for further inefficient voltage regulators. This processing all happens
well above the range of human hearing which, in principal, should be good for
audio circuitry.
What is switch mode?