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Old 25th December 2011, 12:01 PM   #101
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I don't know a single engineer that does not rely on science in order to make a product. I also do not know a single product that does not have that engineer's fundamental sound attribute in the sound. In other words, as transparent a device may be, it still has that X designer's sound to it...as little or a lot it may have, it's there. Same with speakers. You can do anything to make a speaker sound a certain way, but in the end, you can still hear that underlying/fundamental sound that driver makes.

Measurements are always very important, but "reproduction" of anything, will always be just that...something that is in the world of subjectivity. No two ears are the same, even if ears can be so good enough to tell what is what or they can give the basics of what is heard (even if 99.9% say it sounds otherwise)...but it doesn't mean what these golden ears say is right/wrong/the truth/etc.

Audio, as with any subjective aspect of life, will ALWAYS and indefinitely be just that, a subjective experience.
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Old 25th December 2011, 12:17 PM   #102
wahab is offline wahab  Algeria
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Quote:
Originally Posted by ThorstenL View Post
I don't know, I quite fancy the AD811 and LM6181 for "much better than 553X"...
They are not...

Being CFB op amps yield a high slew rate , wich surely did impress you much,
but looking through the details ; you ll see that the AD811 has hardly better
linearity in the audio band than the NE553X , while the LM6181 probably
is much worse in this respect , NS doesnt even bother to publish
THD vs FREQUENCY graphs.

As for the more common VFB op amps , like the 627 , just look at their
GBW products graphs, compare it to the one of the 553X and you can
see all the "progress" that has been made since the late 70s....
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Old 25th December 2011, 12:18 PM   #103
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by tvrgeek View Post
For the problem he was solving, it is quite reasonable that the 553x fully met his needs.
Maybe they met HIS needs.

But based on the results some of his customers got and their reactions to the results, it failed to meet their needs...

Which is why they paid people a lot of money to rebuild the Soundcraft Recording Consoles, including fixing the grounding wiring problems (appallingly bad and equally an appallingly basic thing to get wrong) and changing to higher performance Op-Amp's among other measures...

Ciao T
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Old 25th December 2011, 12:42 PM   #104
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When I was building my speaker's xover I first used resistors and caps that were of typical quality and did FR graphs to get it right.
After I was satisfied I put in Mills resistors and a couple of teflon caps and I had used in other projects, and measured the results.
No difference in FR.
But the music sounded cleaner and clearer.
My simple FR mic (Dayton Audio EMM-6 Electret Measurement Microphone) and software couldn't capture the difference.
An inexpensive Gedlee/Bouska waveguide/tweeter midbass idea.
I'll always use FR in designing xovers, and add in "audiophile" parts in later, as they won't change the engineering part of the design.
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Old 25th December 2011, 12:52 PM   #105
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Hi,

Quote:
Originally Posted by wahab View Post
They are not...
They are, please measure them...

Quote:
Originally Posted by wahab View Post
looking through the details ; you ll see that the AD811 has hardly better linearity in the audio band than the NE553X , while the LM6181 probablyis much worse in this respect , NS doesnt even bother to publish THD vs FREQUENCY graphs.
I have no idea what you are talking about.

It is the Philips (and on-semi and others) datasheet that shows no distortion information whatsoever. While LM6181 datasheet on the TI site does not show the HD graphs, the datasheet for the dual part does though.

More critical perhaps is that the AD811 and LM6181 (et al) are characterised for distortion at 100 or 150 Ohm load. At 600 Ohm load or 2K load they perform much better and the performance of the 553X at 100 Ohm load is one they never bothered to publish (wisely so).

Quote:
Originally Posted by wahab View Post
As for the more common VFB op amps , like the 627 , just look at their GBW products graphs, compare it to the one of the 553X and you can see all the "progress" that has been made since the late 70s....
The OPA627, as well as AD811 and LM6181 are also quite aged parts (if not already discontinued) and not recent.

And why focus on GBW, why not (for example) distortion?

Oh I get it.

We cherry pick specifications that are either not given or not directly comparable or fail to show advantages and then make a big song and dance about it claiming "look, what he said is wrong".

You may find it more useful to actually measure said devices...

Ciao T
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Old 25th December 2011, 01:21 PM   #106
wahab is offline wahab  Algeria
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Quote:
Originally Posted by ThorstenL View Post

I have no idea what you are talking about.
They both have higher THD in the audio band than the old dude....
Quote:
Originally Posted by ThorstenL View Post
More critical perhaps is that the AD811 and LM6181 (et al) are characterised for distortion at 100 or 150 Ohm load. At 600 Ohm load or 2K load they perform much better and the performance of the 553X at 100 Ohm load is one they never bothered to publish (wisely so).
At such low loads , surely that such high current op amps
probaly do better......

Quote:
Originally Posted by ThorstenL View Post
And why focus on GBW, why not (for example) distortion?

Oh I get it.

We cherry pick specifications that are either not given or not directly comparable or fail to show advantages and then make a big song and dance about it claiming "look, what he said is wrong".

You may find it more useful to actually measure said devices...

Ciao T
You are quite paradoxal since GBW product will inherently be a
parameters of first importance for perfs once we apply NFB,
do we , to those circuits , in the aim to reduce....THD !!..

At 1 khz , the NE5532 OL gain is still 100 dB while the OPA627
has collapsed to 85 dB and the OPA134 at 80db.

Now , at 20KHz , the numbers are 65 dB , 59 dB and 53 dB respectively.

Curiously , when restricted to audio frequencies , the NE5532 has higher
GBW product than those two well regarded op amps , it s only below 100 HZ
that theses "audiophile" products have higher gain and thus higher GBW product ,
exactly where it is not needed at all since at those frequencies
there was already enough gain and thus NFB available...

Basically , those two more recent op amps have higher DC gain
but lower AC gain and their linearity (read low THD) is due to better
manufacturing processes than the one available at the time of
the NE553X wich has notoriously slow lateral PNP transistors,
yet , it s still unsurpassed to these days for audio purposes, and when it is , it s only marginally..
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Old 25th December 2011, 02:17 PM   #107
tvrgeek is offline tvrgeek  United States
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"only marginally". Of course. As one gets closer and closer to perfection, in any endeavor, the margins get smaller and smaller for the effort/cost involved. That's the old 90/10 rule. The first 90% takes the first 90% of time/cost whatever, the last 10% takes the other 90%.

I do remind some of the folks here that the basis for this thread is there is some effect that is not currently understood that causes differences in the audible perception of an amplifier. Something is effecting the dynamic transfer function. This is not something we have today on the data sheets. If it was, John, Nelson, and many others would have eliminated it long ago. (they may actually have, just on a price range I can't play in) What ever it is, it is very small and not everyone can either hear it, or if they hear it, be bothered by it. I would ask that some of the lucky majority who can not hear the differences between decent amps would not be so forceful in claiming because they can't hear or measure a difference, there is not one.

I sadly agree high end is a fading market. It seems portability and ease outweigh quality in not just audio, but in most consumer products. In audio, most of the current generation is half deaf from iPods, car stereos, or metro background noise. Unfortunately, most who have served on active duty do not have all their hearing. They see no reason to waste money on subtle differences they can't hear, and rightly so. They will need the cost of a decent amp for their first hearing aids.
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Old 25th December 2011, 02:28 PM   #108
SY is offline SY  United States
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Quote:
Originally Posted by tvrgeek View Post
I do remind some of the folks here that the basis for this thread is there is some effect that is not currently understood that causes differences in the audible perception of an amplifier.
No, not really. The effects which cause amplifiers to be audible are all well-understood and well-documented. The questions then become commercial:

1. Do I want to market an amplifier whose output is audibly indistinguishable from its input?
2. If not, which colorations are desired in my target market?
3. If so, how do I differentiate my product from all the other products which are competently designed to that same goal?


Note that I'm talking about boxes of gain. Transducers are far more complicated.
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Old 25th December 2011, 03:16 PM   #109
tvrgeek is offline tvrgeek  United States
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We will have to agree to disagree SY. You criteria are quite valid. But, some amps succeed in whatever it is that causes what we are hearing. Others do not. There is an audible effect that although not inherent as some amps do not have it, but not understood as others do, and in a price range where if the issue was understood, it would be addressed.

As the mail was slow and I did not get the parts I ordered, I can't start again on this on my day off tomorrow. I may just have to sit back and listen to music through the Rotel's I have that do not seem to exhibit the effect and enjoy a few well crafted products from the Anchor Brewing Company of SF. If there is any product that the good old US of A can make head to head with anyone, it is Porter!

BTW, SY, are you familiar with the A/B box test David Hafler did back in the 80's. Very convincing about no difference with in vs out, but at a steady state. I may try this basic setup but with dynamic inputs to see if I can catch anything. My contrived pulse test may make it repeatable enough to get a picture of it. The DH 120 and 220 are amps he built that passed his test, (or was it a test he designed his amps passed) but my wife informs me do not pass hers. I will then repeat the test with my Rotel. Again, my suspicion, this needs to be done with a real speaker load not a perfect load.

One possible reason for the controversy is that different loads may aggravate whatever the issue is more than others.

As an example, very small amounts of high order distortion can play hell with metal cone drivers if the crossover is not well behaved, yet an easier to use cloth dome may not exhibit the issue. So, is this a fault of the driver or amp? I contend it is "yes" as it is a system problem. The only problem I have with his setup is propagation delay. That may mask the problem. It could also be the problem is not detectable with my scope or analyzer. All this is just words until I can get some pictures.

Wonder if I could get away with snagging an HCA 800-II off the web without the "boss" noticing. I don't really have any excuse for another amp other than testing.
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Old 25th December 2011, 03:25 PM   #110
SY is offline SY  United States
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Yes, I know the Hafler box; it was designed to promote the XL280, if memory serves. There's far better ways of doing the same thing now- for example, the brilliant DiffMaker software. For ears-only listening comparisons, one can easily rig up a high quality switch box (see Linear Audio Volume 2 for a discussion of this).

There are a lot of amplifiers designed to be effects boxes, and there you get into a whole different set of questions. But the reasons that they're effects boxes and the nature of the effects are straightforward engineering.
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