5
SOA Contour following protection
The SOA is the safe operating area of transistors. A good protection system should
respect this area and its shiftings, as the SOA changes as a function of the operating
temperature. So, at 80°C it is considerably narrower than a 25°C, the start-up temperature.
Some manufacturers decide to use protection systems which compromise on the performance
of the components. You get a fair protection, but the performance remains mediocre. Others
prefer to leave "dark" areas between the safe operating area and the activation of protection,
which is very risky indeed.
The new SOA contour following protection systems built into the APA amplifiers
guarantees total protection of the amplifier at any output power, load or operating temperature,
as the intelligent electronic circuitry permanently watches for changes in the safety area,
adapting itself to any situation.
The best Damping in an amplifier of its class. In the APA series, the typical output
relays have been substituted with an electronic CROW BAR system. This device shunts to
ground any signal in case of high voltages which could damage the connected speakers. Any
kind of relay introduces a mechanical contact in the path of the audio signal to the
loudspeakers. This contact implies a certain degree of wearing and an important reduction of
the amplifiers damping factor. To minimize this implicit loss, the use of premium quality relays
is obligatory, as in the professional PAM amplifier series.
3. INSTALLATION
3.1. Location, assembly, ventilation
The APA600/1000/1400 amplifiers are 2 RU high 19'' rack modules.
It is important that the amplifier, as a heat source, is not placed next to other
equipment nor exposed to high temperatures. Therefore, the ventilation path should be kept
free to allow fresh air entering the forced ventilation tunnel. This system takes air from the
unit's backside, bringing it directly to the power amp modules and distributing it to the
transformer and capacitors and then obliging it to pass trough the MOSFET cooling tunnel to
finally blow out of the front panel. In case of rack mounting, this system avoids heat
accumulation inside the unit and thus increases lifetime of electrolytic capacitors. It is
recommended to place power amplifiers on top of other equipment and not underneath.
All APA amplifiers are supplied with plastic washers in order not to damage the rack
ears when tightening the screws.
