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Audio and objectivist epistemology

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When designing an amplifier should the engineer test it's performance by electronically comparing the input and output waves (i.e the distorsion proportion), or by conducting blind tests on a listening group?

Assume that both tests compare one design with another, in order to decide which one goes for production.

"Better sound" means sound that is more similar to whatever was recorded.

What if the engineer conducts both tests and gets contradicting results? should he trust the electronic test or the listening test?

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I sell high end recording and audio equipment for a living and here is my take.

When "recording" music it doesn't seem like there is a right or wrong way to do anything. Part of producing and mixing is coming up with a certain sound. Whether the sound is accurate or not is not always what you want. Classical music wants accuracy while other forms do not. An electric guitar amp has lots of distortion and effects. The dry electric guitar signal really isn't used much. All genres have certain sounds people are accustomed to like Country=Twang, Metal=Heavy Guitars, Hop-Hop=808 Bass. So a country producer in order to sell more CD's wants it to appealing to as many Country fans as possible.

For PA amps or high end home stereos the more accurate uncolored the signal the better. That way the original source music is reproduced as accurately as possible. Its amazing how much more nuance and fidelity can be heard when listening to music on a nice system.

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  • 1 month later...
When designing an amplifier should the engineer test it's performance by electronically comparing the input and output waves (i.e the distorsion proportion), or by conducting blind tests on a listening group?

In the high-end press, these views are called "objective" and "subjective" respectively. But they are both misnomers.

Measurement is only useful so long as one knows to measure. I think a really good example of this comes from early CDs. They had really low wow and flutter, low harmonic and intermodulation distortion, low noise, good channel separation, flat frequency response, and excellent dynamic range.

But they sounded like shit.

Eventually, digital engineers discovered jitter, and it turns out that this is one of the most important kinds of distortion affecting CDs. Low jitter means better.

Ever since Nelson Pass' papers on zero global feedback amplifier design, the high end world has been discovering designs that avoid global feedback and keep local feedback to a minimum. I am not sure what kind of distortion is caused by global feedback in terms of measurements, but I understand it at the conceptual level. Since every transistor, wire, etc. has a finite time to pass the signal, feedback always lags the real signal by a small amount of time. This smears what had been sharp transients. Does this manifest as harmonic or intermodulation distortion? I dunno.

So the flip side says: who cares how it measures. Just listen to it! I can recall a cartoon in Stereophile about 10 years ago that shows three guys sitting down to review a piece of gear. There was a guy who looked suspiciously like Julian Hirsch. He had a banana rammed halfway into each of his ears. He said "It measures well." The next guy I think was J Gordon Holt, and he said "It sounds awful." And there was a third guy who looked like a punk rocker who said "It's loud, man!"

I think a reviewer should mostly focus on the sound, and discuss measurements only where relevant. But for the engineer designing the circuit, it's different. He needs principles to guide him to designs that sound good; he can't just build an infinity (heh) of designs and listen to them all.

Just my $0.02.

For the record, I love the old Threshold sound, the amplifiers based on the Nelson Pass designs. I look forward one day to auditioning the new Pass stuff, particularly the XA series.

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  • 4 weeks later...
When designing an amplifier should the engineer test it's performance by electronically comparing the input and output waves (i.e the distorsion proportion), or by conducting blind tests on a listening group?

Assume that both tests compare one design with another, in order to decide which one goes for production.

"Better sound" means sound that is more similar to whatever was recorded.

What if the engineer conducts both tests and gets contradicting results? should he trust the electronic test or the listening test?

The purposes of "perfect reproduction" and "make it sound *good*" are not the same. That means that at some point, they will diverge.

The recent resurgence in tube amps shows that all too well.

So the answer to your question depends on whether the engineer seeks mathematical perfection, or want to sell a lot of amps. With the degree of precision now possible, the remaining variables all pertain to personal preferences.

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