accessories for the Crescendo power amplifier - countdown and d.c. protection circuit and d.c. protection circuit

the accessories for the Crescendo elektor january 1983 Elektor readers who are hi-fi enthusiasts will no doubt have read the Crescendo article in the December 1982 edition. Some will already have started building the power amplifier. Once constructed, tested and installed in an attractive cabinet, the ampli- fier should operate reliably and with consist- ent quality for years. However, there is always a chance that a component will fail in the course of time or that some other malfunction will occur. In such cases, for example, it is possible for a d.c. voltage to reach the amplifier outputs and destroy the expensive loudspeakers. The latter are simply not designed to cope the amplifier outputs by means of a relay, exactly five seconds after switch-on. Sec- ondly, it continuously monitors for an excessive d.c. voltage at the outputs. If this voltage exceeds a particular value, the links between the amplifier and the loudspeakers are disconnected. The operating voltage for the prot...