Linn KLIMAX CHAKRA 500 Twin, Owner'S Manual

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4
Features
Power supply
In most power amplifiers, the power supply comprises a large transformer, a rectifier and reservoir
capacitors, which are often as large as the transformer itself. The highest performance amplifiers also have
voltage regulators which maintain the power supplied to the amplifier circuitry at a constant level,
regardless of the input voltage or the output load. The size of these components dominates the amplifier’s
dimensions and affects the 'tightness' of the audio path, and if voltage regulators are present the power
dissipation of the amplifier increases by up to 50%. This conventional type of power supply is simple,
reliable, tolerant of overload and predictable. On the down side it is very bulky, heavy, slow to respond,
inefficient, causes high mains power distortion, can cause electrical and acoustic noise and requires a
relatively long and exposed audio path.
In the KLIMAX amplifiers we use a technology that we have been developing and using in our low power
products for several years, called 'switch mode'. This concept is not new; it has been used in computers since
the 1960's, however applying it to audio was generally considered, at best, inappropriate.
The potential downsides of switch-mode in audio devices are electrical noise, high complexity and
potentially lower reliability, complex certification requirements, design difficulty and high engineering cost.
These drawbacks have kept switch mode out of most audio equipment.
On the other hand, the potential benefits of switch mode power supply technology are compactness, high
efficiency, fast response, good mains input tolerance, good load tolerance, low acoustic noise and, with its
low material use, environmental friendliness.
What is switch mode?
In a switch mode power supply the incoming mains is filtered then rectified to generate a very high voltage
dc (direct current) supply - usually of 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.
This high voltage is chopped up by very fast semiconductor switches and applied to a small transformer
which both converts the voltage to the value required 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 a fraction of the size of 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 is
beneficial in situations where audio circuitry is involved.