Analogue & digital

Leafing through some electronics magazines published over the past few years, it is surprising how fast and vigorous digital techniques have come to the fore. Even audio, until recently virtually untouched, is now becoming digitalized at a rapid pace. What are the consequences of these changes to us engineers, tech- nicians, and hobbyists alike? As long as a circuit is totally analogue or totally digital, all is well. But as soon as these two techniques become mixed strange things some- times happen. Well-known examples are analogue-to-digital converters that will not give a stable reading: the last few digits do not match and it appears as if there is a certain regularity in the deviations. Another example is an otherwise good ampli- fier that generates whistles in perfect rhythm with the digital clock oscil- lator. And so on . . . Often, these flaws can be traced to faulty earth connections, i.e. the zero analogue & digital 521 supply line, or common ground. Because of that, her...