Load-invariant audio power
It has been my experience that power amplifiers always, without exception, give more distortion with heavier loading i.e., with a lower load impedance. This, in BJT amplifiers at least, is due to an extra distortion mechanism that becomes more and more important as the load impedance falls and the output stage currents increase. Against all intuition, the source of the increased distortion is the drivers, and not the output devices themselves; this was wholly unexpected, and to the best of my knowledge was a new discovery. It was uncovered not so much by mathematics or theory as by some careful SPICE analysis, later backed up by measurements, and was a copybook example of just how very powerful and useful circuit simulation ...
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