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Old 12th January 2013, 05:06 PM   #32551
SY is offline SY  United States
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Quote:
Originally Posted by john curl View Post
Better to stick with the simple and store bought, for most of you.
We unwashed masses are too busy staring at the ground and drooling.
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Old 12th January 2013, 05:08 PM   #32552
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Originally Posted by Esperado View Post
Again, John, "quality" means nothing, it is just marketing blah blah.
How do-you define-it ?...
John did define quality in the post you were answering to. Do you read
your own posts only ? Is your only goal to make comments like the one
you just did ? Probably quality means nothing to you, but for others it does.
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Old 12th January 2013, 05:19 PM   #32553
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Well, SY, you are doing OK. You bought my Alps pots, years ago.
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Old 12th January 2013, 05:27 PM   #32554
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Yes, I sold SY some of my extra pots left over from previous projects. He was very appreciative at the time. Things change, I guess.
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Old 12th January 2013, 05:40 PM   #32555
RNMarsh is offline RNMarsh  United States
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I relate quality to reliability and long life and performance all together.

10 points each - bonus points of (1 each) for looks and value.

-RNMarsh

Last edited by RNMarsh; 12th January 2013 at 05:45 PM.
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Old 12th January 2013, 05:51 PM   #32556
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Richard, it is more than that. It is using the RIGHT part for the job.
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Old 12th January 2013, 06:00 PM   #32557
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Quote:
Originally Posted by PMA View Post
Similarly as in Scott's link (Ed's image). 80dB is a noise gain and 0dB (= gain +1) is a signal gain. Try OP177 datasheet, Figure 26, e.g.
Careful PMA this is the inverting version of distortion amplification, it does not rely on synthetic input resistance. The non-inverting version is related to gyrators, SRPP, etc. and I don't think think yet that Ed see's that the test circuit is no load on the generator i.e. the generator impedance does not matter at all and to the first order there is no signal current in either resistor.
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Old 12th January 2013, 06:15 PM   #32558
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Quote:
Originally Posted by scott wurcer View Post
Careful PMA this is the inverting version of distortion amplification, it does not rely on synthetic input resistance. The non-inverting version is related to gyrators, SRPP, etc. and I don't think think yet that Ed see's that the test circuit is no load on the generator i.e. the generator impedance does not matter at all and to the first order there is no signal current in either resistor.
Scott,

I don't think you got my reference to the parable of the blind men and the elephant. Each looked at parts and thought they had the whole.

Making standard measurements of the AP is mostly autopilot. If you don't pay attention to the details you get very pretty graphs of nonsense.

Attached is a THD curve that shows the noise limit and the maximum voltage out of the unit. (It gave me an error message when I tried higher source voltages.)

The second attachment is the best curve of the LM4562 as there is a gain of about 100 be sure to reduce the label values.

I showed you the current source version of the test circuit as shown in the data sheet. Now from prior questions it seems almost no one here can even write the loop equations, which I thought were obvious from inspection.

Trying to get the same view of the Elephant how do you read the limit of the AP trying to display what is shown?

ES

PS I see I forgot to do log on the voltage so the graphs don't look the same!
Attached Images
File Type: jpg 100 THD vs Level.JPG (54.8 KB, 181 views)
File Type: jpg LM4562 THD.JPG (59.7 KB, 178 views)

Last edited by simon7000; 12th January 2013 at 06:20 PM.
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Old 12th January 2013, 06:21 PM   #32559
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I remember those caps we used to build our amps in 70, bought near a French manufacturer . It was their 'top quality' line.
It is only 20 years after that it was sure they were pure junk, all dry.
That is the sens of my question. I believe audio parts are engineering, defined by their characteristics, on catalog then measurements, not vine or fashion.
About pots, my question was not so insane: what can-we measure to ensure a pot is a "quality" parts. Of course, i got no answer.
Quote:
Originally Posted by gk7 View Post
John did define quality in the post you were answering to. .
No, or we don't have the same definition of "define". It is like "Right part".
If you dislike my comments, please, just add me in your ignore list, as i do for you right now, for the same reason and with my best regards.
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Old 12th January 2013, 06:41 PM   #32560
SY is offline SY  United States
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Quote:
Originally Posted by john curl View Post
Things change, I guess.
How so? They all found good use.
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