PA300 power amplifier
PA300 power amplifier
Taken by themselves, the properties of thePA300 amplifier are not revolutionary. Buttaken in combination, they show somethingspecial: a robust 300 watt hi-fi poweramplifier that is not too difficult to build.
There are several startingpoints to the design of apower amplifier: pure hi-fi withoutany compromise; simplicityand reliability; high outputpower. The design of the presentamplifier is a mixture of these.The result is a unit that does notuse esoteric components, is nottoo complex, and is fairly easilyreproduced. In fact, it could wellbe named a ‘Hi-fi public addressamplifier’.There will be a few eyebrowsraised at the power output of300 watts (into 4); it is true, ofcourse, that in the average livingroom 30–40 W per channel ismore than sufficient. However,peaks in the reproduced musicmay have a power of 10–20times the average level. Thismeans that some reserve poweris desirable.
Also, there are loudspeakersaround with such a lowefficiency that a lot more than30–40W is needed. And, last butnot least, there are many peoplewho want an amplifier for roomsmuch larger than the average livingroom, such as an amateurmusic hall.Straightforward designSince every amplifier contains a certainnumber of standard components, the circuitof F i g . 1 will look pretty familiar to mostaudio enthusiasts. Two aspects may hit theeye: the higher than usual supply voltageand the presence of a couple of ICs. Thefirst is to be expected in view of the poweroutput. One of the ICs is not in the signalpath and this immediately points to it beingpart of a protection circuit.