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Chip Amps Amplifiers based on integrated circuits

LME49720 Vs LM4562....
LME49720 Vs LM4562....
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Old 11th April 2018, 04:58 AM   #51
mrkaic is offline mrkaic
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Quote:
Originally Posted by P.Lacombe View Post
"Identical" chips can in fact be slightly different. Depending on production batch, criteria of acceptance, an so on. This is particularly the case with NE5534 : Many years ago, I have tested lots of this device (Signetics, Philips, TI...). But I am retired and now I do not own sufficient quantities of LMxxx from various manufacturers to make a serious study on this question.

The "sound" of one particular AOP is depending essentially on the good or bad adaptation in one particular circuit, simple thing such decoupling capacitors can affect very diversely the total net result...
Can you prove that in a blind test?
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Old 11th April 2018, 04:59 AM   #52
mrkaic is offline mrkaic
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Originally Posted by johnego View Post
Exactly.

I have many LF353 from various manufacturers and the best sounding one came from Comset Semiconductors.
Can you prove that in a blind test?
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Old 11th April 2018, 05:09 AM   #53
Circlotron is offline Circlotron  Australia
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Originally Posted by BrassTeacher View Post
I actually e-mail the tech people at National. They said yes, the only difference is the number stamped on the outside.

BT
Some people would believe merely that is enough to change the sound...
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Old 13th May 2018, 01:53 AM   #54
johnego is offline johnego  Indonesia
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Originally Posted by Circlotron View Post
Some people would believe merely that is enough to change the sound...
The minimum and maximum difference in the characteristics specification is sufficient to make two chips of the same type to sound different!

When big manufacturers decided to move their plants to china and asian countries, nothing they can do control the minimum quality of the product and what will happen to these products (it can go out through the windows and roofs).

Here in my country you can buy at least 5 different LME49720 chips. Sometimes, the best one (the most expensive) is called "original" and the next best thing is "KW1", "KW2" and so on.

I have learnt (from transistors) that these low quality parts are not always fake (it's original with a caveat).

You should not listen to people who compares opamp based on these low quality parts (it is not a fair comparison, besides they dont understand that different opamp needs different treatment). The parts from asia is not supposed to be sold to US but I think ebay and the like is free for US citizens.
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Old 13th May 2018, 06:45 AM   #55
diyralf is offline diyralf
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My old saying: Do not buy chips on ebay.
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Old 13th May 2018, 01:38 PM   #56
FauxFrench is offline FauxFrench  France
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Johnego, I believe many IC design companies (called manufacturers though they don't manufacture) have lost control with the items being sold on the world market, claiming to be an original product. The use of various foreign wafer production sites through decades makes tracking very difficult.
My understanding from the past of IC manufacturing was the ICs would be tested, at least for basic parameters, on wafer-level such that the clearly deficient items would be discarded before being put in a housing.
Would you know if this is still the case? Or, is the problem the foreign wafer houses produce batches where the testing is much more lenient than for the official products?
I believe no large scale IC production has taken place in Europe for more than a decade. We simply don't know what's going on anymore.

Last edited by FauxFrench; 13th May 2018 at 01:45 PM.
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Old 13th May 2018, 01:57 PM   #57
diyralf is offline diyralf
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I think that's a nice wishful thinking. It seems that only random sampling are being tested. LinearTech has ops that are 100% tested. But of course they cost $10 and are not suitable for audio. AMD has made PC processors in East Germany for a long time. When the State did not want to pay anymore, the fab was closed.

Last edited by diyralf; 13th May 2018 at 02:05 PM.
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Old 13th May 2018, 03:16 PM   #58
FauxFrench is offline FauxFrench  France
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My modest knowledge goes back to when ICs cost considerably more than today and the photographic masks were an important way to protect against copying. For the ICs discussed in those days, 100% testing of essential parameters was foreseen (wafer-level). Today, the masks are no doubt replaced by a data-file and the production robots no doubt much cheaper. So, with a copy of the data-file, setting up a production of theoretically "original" products, to the extent the production gear is good enough and maintained well, may not be costly. But, then comes the yield and the screening as variable parameters. A complex situation.
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Old 14th May 2018, 03:26 PM   #59
BrianL is offline BrianL  United States
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LME49720 Vs LM4562....
Johnego, whatever is sold in your country is likely counterfeit. If you go to ti.com and look up the options, you will not see different grades of LME49720. As was stated above, be careful where you buy them.

As far as test flows, TI generally does 100% testing after packaging and many product are also tested at the wafer level. All reputable companies will use a combination of wafer-level die testing and 'final testing' to test all parameters with minimums and/or maximums on the datasheet; any deviations from this practice will likely be indicated with footnotes. Despite advances in semiconductor technology, there remain certain levels of 'defect density' on wafers even if the fabrication process itself were perfect (which it isn't). Customers are also demanding higher outgoing quality levels so skipping test steps is not a viable option if quality goals are to be met.
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Old 14th May 2018, 04:46 PM   #60
FauxFrench is offline FauxFrench  France
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Thanks for the clarification, BrianL.
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