At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become “dirty”. If this happens too often or is too severe, tweeters are the first to go
Many clipping detector circuits have been published over the years, but most of them rely solely on an attenuated (reduced) version of the output signal, supplied to a suitable comparator circuit.
This would be fine if the mains voltage stayed exactly the same at all times, and if the power supply had perfect regulation. The fact is that neither of these is true, and the amplifier’s DC supply voltage can vary quite considerably from hour to hour, and even minute by minute.
The clipping detector shown here relies on one factor – how close to the supply voltage is the amplifier’s output signal at any instant in time. If (when) the supply voltage varies, the detector varies along with it, and will detect even a very short peak that crosses the detection threshold.
The Clipping Detector
Figure 1 shows the circuit of the detector. Although a simple circuit, it uses a principle of operation that will be new to many readers. Indeed, it is new to me as well, since this is a method of detection I have never seen published in this form. There was one detector published many years ago that was similar in some respects (this was pointed out by a reader after this circuit was published), but it was dramatically more complex and included extra functionality that (IMO) is best kept separate.
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