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Old 22nd January 2013, 04:21 PM   #33311
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Default Subjective Evaluations ?...

None of the good opamps (OPA627, AD797, OPA134 ...) has any residual 7th above -120dB. They do not sound same, but the 7th is not the reason.
Hello again Pavel, I respect your measurements data, that said it reads that you are making subjective comment here. Could you please elaborate on your subjective findings of these opamps, or at least your subjective findings of differences between this collection of opamps.

Thanks, Dan.
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Old 22nd January 2013, 04:31 PM   #33312
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Dan,

it is pretty difficult and subjective.

From the set here, I like most OPA637 and AD844.

AD825 sounds "nice", but it wipes off differences in quality of different recordings, equalizing them a bit - to me.

AD797 is a very good opamp but I prefer AD844 and OPA627/637 for line level, they sound more cultivated to me. IMO this is because of the worse immunity of AD797 to interference.
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Old 22nd January 2013, 04:59 PM   #33313
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Please give it a break, PMA. 7th harmonic is STILL very important. I challenge YOU to make something better than my designs, rather than 'bad rap' me.
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Old 22nd January 2013, 05:03 PM   #33314
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No one said it wasn't. What was challenged was your apparently incorrect claim that it is what distinguishes ICs from discrete, relegating the former to "mid fi."
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Old 22nd January 2013, 05:04 PM   #33315
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Quote:
Originally Posted by Max Headroom View Post
None of the good opamps (OPA627, AD797, OPA134 ...) has any residual 7th above -120dB. They do not sound same, but the 7th is not the reason.
Right, Dan. The question remains, witch is the only interesting (and mysterious) one: WHY ?
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Old 22nd January 2013, 05:06 PM   #33316
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Quote:
Originally Posted by jneutron View Post


It's best to think of it as the current is trying to take the path of least reactance. As frequency increases, the path becomes the lower inductance path. For a wire pair next to each other, that path is as close to the other conductor as is possible given the fields. for a coax, it is the surfaces closest to one another.

Thsi also occurs on PCboards with a full ground plane, and also within chassis when ground current is flowing through the chassis, and when equipment is connected via more than one ground.

I agree with all this part. It is all documented in any book on the subject. Nothing new here. -RNM

jn
I agree also with the inductance vs freq....goes to path of least resistance... towards the surface of the conductor where the L is lowest.
Do not agree on your explaination regarding the fields. Perhaps just a different view of the same thing? -RNM
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Old 22nd January 2013, 05:07 PM   #33317
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Default English Can be A Powerful Language...

Cultivated
Synonyms: accomplished, civilized, educated, enlightened, learned, polished, refined, sophisticated, urbane.

Ok, not a term I have heard or used to describe audio equipment, but I think I get the picture...maybe.
Interesting that these opamps that all measure close to perfect (low ppm distortions) should elicit subtly different subjective opinions.
Nonetheless, you have provided a shortlist and give me the inspiration to do some ordering and soldering in order to take a closer listen for myself.

Thanks and regards, Dan.

PS - Anybody here have same or different subjective opinions of this collection of opamps when used in line level applications such as volume control recovery amp or line output driver ?.
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Old 22nd January 2013, 05:13 PM   #33318
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Quote:
Originally Posted by john curl View Post
Please give it a break, PMA. 7th harmonic is STILL very important.
Yes it is, but it is non-existent in good opamps up to 40dB gain in any audible level. I support the answer that SY gave to you. Please stay technical and at engineering level.
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Old 22nd January 2013, 05:18 PM   #33319
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Let me explain the situation as I see it.
A number of comparisons of THD (the easiest measurement possible) at 1KHz,(the easiest frequency possible) with MAXIMUM feedback applied, to the point of absurdity, where something else would be a better solution, just to MASK the inherent non-linearity in the AD797, and hide its intrinsic properties.
For the record, I seldom MEASURE IC op amps, anymore. I just LISTEN to them, as I did with the AD797. I would have included it in my JC-3 phono design, but I found another IC that sounded just as good, at less than 1/2 the price, with the same basic specs. I avoided using the AD825 for the second stage, for other practical reasons. I suspect, all else being equal, it would sound better than the OPA134 that I selected, but I needed a DUAL op amp, not a single.
Harmonic distortion is useful ONLY when a frequency sweep is used as well as a low residual. Heck, you might as well use SMPTE IM. It is more sensitive to many nonlinearities, so why not? Where are the SMPTE IM analyzers with a resolution to .0000001? I sure could use one.
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Old 22nd January 2013, 05:21 PM   #33320
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Default The Ultimate (Audio) Question...

Quote:
Originally Posted by Esperado View Post
Right, Dan. The question remains, witch is the only interesting (and mysterious) one: WHY ?
With all the brainpower collected here, we still don't have the answer it seems.
I do know that the answer is not 42 .

Dan.
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