40 watt main amplifier

elektorjuly/august 1983 78 40 watt main amplifier Our December 1982 issue featured the 2 x 140 watt Crescendo; here we describe the circuit for a main amplifier for those with more modest power requirements. A normal ampli- fier which is, however, not so normal. The output stage contains two type 2N3055 power transistors: proven, reliable components. At first sight it appears that the output stage is not symmetrical because transistors T15 and T16 are NPN types but a second look will show that it is: the top half consists of NPN "supertran- sistor" T11/T13/T15, while the lower half comprises PNP "supertransistor" T12/T14/T16. These "supertransis- tors" are complementary: as their emitters are connected together via R25... R27 and R28... R30, the output stage is symmetrical. The remainder of the amplifier is also constructed symmetrically: a double differential amplifier, T1/T2 and T3/T4, current sources T5 and T6, followed by driver stages T7 and T8. The output power is 40 watts i...