Some of the best-sounding audio systems in the world are measurably imperfect — and understanding why might tell you something important about how sound actually works.
Here's the basic physics. When an amplifying circuit processes a signal, it can add overtones — frequencies that weren't in the original. This is distortion. Solid-state designs tend to produce odd-order harmonics: the third, fifth, seventh. These are mathematically unrelated to the fundamental tone, and in any meaningful quantity they can sound harsh, edgy, and fatiguing. Tube circuits tend to produce even-order harmonics: the second, fourth, sixth — the same overtones often present in acoustic instruments and the human voice. Your ear has heard them all your life. They don't always register as an error. They can register as character.
The real goal in any audio design is to push distortion as low as possible. The new PMG amplifier series achieves distortion well below 0.0015% — that's less than one part in a hundred thousand — which is effectively inaudible under any listening condition. We measure this with an Audio Precision system capable of resolving to nearly -120dB, which is extraordinary precision. And yet even at these vanishingly small levels, two amplifiers with nearly identical distortion figures on paper can sometimes sound different in a listening chair. What the instrument captures is quantity. What it might not capture is character — whether the residual distortion products are even-order harmonics the ear tends to accept naturally, or odd-order ones that don't quite belong in the musical picture.
This isn't an argument for tolerating distortion. It's an invitation to understand it.
Measurements are essential, and as designers and engineering nerds we'd be lost without them, but they may not tell the whole story. We already have the world's most finely calibrated measurement instrument on either side of our heads, one that's been training on live sound our entire lives.
We don't fully understand how aspirin relieves pain either, but it still works. The listening experience is data — and in the end, that might be the measurement that settles the question.
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