Imagine for a moment two analog gain blocks, each with identical input and output impedance as well as gain.

To make our little thought experiment more interesting, let’s also imagine their THD and IM measurements are identical as well.

Now, here’s where it gets juicy. Let’s imagine circuit A is a traditional high open loop bandwidth amplifier with lots of negative feedback applied to establish its gain. Circuit B is the opposite. Here we have a circuit with very low open loop gain with very little negative feedback.

Would the two sound different if we played music through them and listened on a highly resolving system?

Having made this comparison more than a few times I can tell you my own findings are pretty clear. Indeed they do sound quite different, especially when the type of music we’re using has lots of rich harmonics and overtones played in a non-cluttered setting where those overtones can easily be heard.

It’s in fact not even a contest. Instantly noticeable and consistently the same even in blind testing.

But, why? What measurements might we apply to see those differences?

A differential null test?

Why haven’t we, as an industry, together created a measurement system that clearly demonstrates those differences on a measurable basis?

And even if we did, would anyone care?

Paul McGowan / PS AUDIO

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