John Curl's Blowtorch preamplifier part II

[Soundminded]

Originally Posted by john curl

SY, I insist on .1dB response to 20K, not 100K.

What is the engineering justification for that specification? Why not .01 db or .001 db. Where does that come from?

[scott wurcer]

Originally Posted by Soundminded

What is the engineering justification for that specification? Why not .01 db or .001 db. Where does that come from?

Digital RIAA can easily do .0001dB and .001 degree phase.

[john curl]

I just like the sound of .1dB. Have been doing it for 30 years. Too old to change. However, how do I get it right, everyone? I use my trusty HP3563, set it to audio sweep and note the deviations. Looks like the Rocky Mountains still!

[Soundminded]

Originally Posted by scott wurcer

Digital RIAA can easily do .0001dB and .001 degree phase.

I'm not surprised. But my question to JC is what demonstrated criteria is the specification based on. An engineer defines requirements based on some functional need. He doesn't wet his finger and stick it in the air to see which way the wind is blowing that day. So what I'd like to know is how did JC arrive at his spec? If he were to tell me that a documented study shows that 95% of people can hear a difference of +/- 0.2 db at 20khz and he wanted a 100% safety margin then I could accept that. What I can't accept is that he tells me in one breath he's an engineer and in another that he selects a performance specification that his equipment must meet out of thin air because that's what he likes or because that's "his" experience. Engineers, that is real ones have a rational reason for what they do. If they don't, then it's not engineering. It may be advertising but it's not engineering.

[Joachim Gerhard]

I found this :
Audio, Meet Science | Stereophile.com
Maybe John is a "Real Life Engineer".

[Soundminded]

Originally Posted by Joachim Gerhard

I found this :
Audio, Meet Science | Stereophile.com
Maybe John is a "Real Life Engineer".

Specific tests may not be valid for a number of reasons. The science isn't sufficiently advanced to devise meaningful tests that examine salient variables. The tests fail to simulate real world conditions but are inherited from a more primitive time when they were once meaningful. There are more variables in the test procedure than it controls and one variable at a time is not being tested but multiple variables are at work simultaneously. There are others.

That tests are flawed does not negate the fact that they are the only reliable way to determine the limits of perception among those being tested. The claim of the so called subjectivists is that the process of testing itself is not valid. Nothing could be further from the truth. The problem for someone who genuinely believes he has made a discovery or devised something truly innovative is to devise a test which proves it. That is exactly the opposite of what audiophiles do. They only use tests and measurements to justify opinions when it is convenient to prove a point they arrived at irrationally and when the opposite is true, they reject the idea that tests prove anything. Now what about that blowtorch preamplifier?

[Steve Eddy]

Originally Posted by Soundminded

Engineers, that is real ones have a rational reason for what they do. If they don't, then it's not engineering. It may be advertising but it's not engineering.

Let's examine that statement.

Ultimately, the end goal is to sell product and make money.

That requires marketing and advertising.

And in this market, as with many others sadly, playing the numbers game is a highly effective marketing tool.

The numbers are achieved through engineering.

Therefore, does the engineer in this case not have a rational reason for what they do?

Surely you're not arguing that the desire to make money is irrational are you?

se

[john curl]

I hate to say it guys, but the reason I use .1dB is because I can, with 1% parts and a good engineering design that optimizes the tradeoffs. That is all there is to it. The very idea that Lipshitz might think that it is important, only contributes to my effort. After all, RIAA has been essentially defined by Lipshitz and Jung. That is what I use to map to.

[Joachim Gerhard]

Here is evidence that at least one cutting room uses a second order rolloff on the lathe.
Combined with the infamous "Neumann Pole" the result is worse then leaving it alone.
Cut and Thrust: RIAA LP Equalization | Stereophile.com

[jacco vermeulen]

Originally Posted by Soundminded

an engineer selects a performance specification that his equipment must meet out of thin air because that's what he likes or because that's "his" experience.

In my vocabulary, that just about sums up an engineer.
While on the other hand, you seem to view an engineer and a scientist as one and the same.
Must be a language barrier thing.