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Old 20th January 2013, 03:02 PM   #33071
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Thanks for putting up the complete article, Electroj, but I do not know if I have the second part. It all depends on old issues of IEEE papers.
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Old 20th January 2013, 03:13 PM   #33072
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That depends on circuit, load, and level, no? I have no personal experience with those, so am agnostic. Likewise, there's no published spectra of the BT, so I have no idea if it's "high end" or not by that definition.
I do, I have my own measurements of dozens of opamps under normal conditions, with standard load like 2k - 10k, 2Vrms, gain 1 - 10. 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. John's fairy tales about the 7th are marketing claims. We can easily find the 7th above -120dB in many so called High End products, as I have linked earlier.
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Old 20th January 2013, 03:18 PM   #33073
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They do not sound same,
Witch one you had listened to, between all OPAs you tested was the closer to a strait wire ?
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Old 20th January 2013, 03:22 PM   #33074
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This is a difficult question, for the reason that line preamp may sound better than the straight wire. IMO the reason is that if you filter HF from digital sources (I mean spikes and D/A residuals) the preamp may sound better.

My favorite opamp is AD844 - for line level.
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Last edited by PMA; 20th January 2013 at 03:29 PM.
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Old 20th January 2013, 03:38 PM   #33075
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This is a difficult question, for the reason that line preamp may sound better than the straight wire.
Throw-it away immediately !
(Or sold-it as a recording studio gear :-)
You are a cheater, choosing a high slew-rate current feedback device :-)

I am searching right now a voltage feedback double opa for DACs (voltage, differential) and i do not find anything fast and quiet enough on the paper.
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Last edited by Esperado; 20th January 2013 at 03:47 PM.
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Old 20th January 2013, 03:50 PM   #33076
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Originally Posted by john curl View Post
Thanks for putting up the complete article, Electroj, but I do not know if I have the second part. It all depends on old issues of IEEE papers.
The study of contacts is an old field of research. The telephone business and power industries used millions of relays all across the country and cities...switch gear... contacts of all sorts had to be reliable and so contacts were heavily studied and materials developed for all manner of contacts from telephones to power switching.

One of the early 'bibles' to find is "Electric Contacts" by Ragnar Holm. My edition is 4th (1967) is published by Springer-Verlag. I added it to my technical library in 1981. You can branch out from here by using its author and literature index. Everything you ever wanted to know and a lot more can be found within this contacts Bible. (ISBN 3-540-03875-2 and 0-387-03875-2)

Thx-RNMarsh

Last edited by RNMarsh; 20th January 2013 at 04:01 PM.
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Old 20th January 2013, 03:51 PM   #33077
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THS4012 ? (i need line drive capability too )
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Old 20th January 2013, 05:27 PM   #33078
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Well PMA, you might be right. After all, reduction of 7th harmonic does not necessarily PROVE a good design, but I will prefer to minimize it.
It is NOT my 'fairy tale' but just my opinion that 7th harmonic is more important than most other harmonics.
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Old 20th January 2013, 05:29 PM   #33079
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I happen to prefer the AD825 for my line amps. I am using it in new designs.
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Old 20th January 2013, 05:36 PM   #33080
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Thanks again, Electroj, for putting up the article that you put up here. I first misunderstood what you wanted from me. What you want is the rest of the article, rather than a second part to the article. I will dig around, it is here, someplace, but I have to individually scan it, so it might take some time.
Richard is right. Holm is the best reference, I have one of Holm's books, as well. Mine is called 'Electronic Contacts Handbook' from 1958. Either book is a real 'bible' for contacts, but quality engineering articles from Whitley (sp) from AMP, will give you even more easily understandable info on contacts.
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