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Old 19th May 2010, 04:44 PM   #4371
PMA is offline PMA  Europe
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Just curious, John -

are you making a survey for our younger colleagues?

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Old 19th May 2010, 06:03 PM   #4372
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PMA, discussion at a very high level, without the grounding that it takes to really understand where we have researched, and what we have learned, tends to lead to conclusions from different groups that is unproductive, as they are not easily resolvable.
For example, high vs low feedback, high vs low open loop bandwidth, higher order distortion generation, etc.
I prefer to start from first principles, learned by me, historically, as to what has worked and what has not, in audio design.
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Old 19th May 2010, 06:15 PM   #4373
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Should we talk about the Fairchild reverbs. The hot studio darling of the early 70's. Lots of 741's. So why did a semiconductor manufacturer start making audio gear?
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Old 19th May 2010, 09:07 PM   #4374
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John:
My core question turns on why they work. Here is a core philosophical question: if the problem is addition (new harmonics) why after passing through a chain of IC based electronics upstream (recording, mixing and mastering stuff plus effects) does the very small added distortion affect the sound so much? Or vice versa do the added distortions somehow make a chain sound better when they are the right distortions? And how can we know?

The history helps ground the discussion.

Fairchild has a long complex history of making all manner of stuff. Fairchild Semiconductor was a spin-off Fairchild Camera and Instrument - Wikipedia, the free encyclopedia At one point Keith Johnson desinged tape recording electronics for them.
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Old 19th May 2010, 09:16 PM   #4375
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Even if the signal passed through many opamps during recording process, the sonic result would be affected by specific stages, like CDP output stage, preamplifier, and power amplifier input stage. This is very interesting, and it indicates that neither PIM, nor high order harmonics are the answer.
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Old 19th May 2010, 09:45 PM   #4376
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Not wishing to hi jack this thread I just want to point you in the direction of a new thread started in "Everything Else" about some new (well at least that is what is claimed in the link) approaches to equipment measurement.
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Old 19th May 2010, 10:42 PM   #4377
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Again, this is the problem. We can conjecture as to the best approach, especially from our own experience and what we have studied.
In any case put forward, so far, the understanding is not as complete as possible.
For example, one might think that low feedback, below 20dB is a problem, another might find that no feedback sounds best, yet another finds that measuring the harmonic order gives a powerful clue, etc. I still have to go forward with what we DO know about aberrations in the musical signal when feedback is applied, and as well note what appears as overwhelming distortion generation by some products that can still sound very good, appropriately used with other compatible equipment.
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Old 20th May 2010, 05:04 AM   #4378
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Quote:
Originally Posted by PMA View Post
Even if the signal passed through many opamps during recording process, the sonic result would be affected by specific stages, like CDP output stage, preamplifier, and power amplifier input stage. This is very interesting, and it indicates that neither PIM, nor high order harmonics are the answer.
Play one direct to disc LP on a good set and you have the answer....
Awesome!
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Old 20th May 2010, 05:15 AM   #4379
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One historical understanding, more than 70 years old, is the relative importance of the harmonics generated, even when amplifying a single test tone. It can be shown that the harmonics are related to the amount of deviation, and the rate of change of the deviation from perfectly linear. In a Class A system, it is fairly easy to predict the distortion levels, once ONE level and its harmonic series is measured. Therefore, you can go up or down in level with predictable calculations. This can give a level of confidence that if you measure the distortion at 1V, for example, that lower output will have a predictably lower amount of distortion with every harmonic. Each harmonic, however, has a different rate of reduction, and that could be important. For example, at .1V you might find more 2'nd than 3'rd, but at 1V, you might find more 3'rd than 2'd, because it rises faster than second with level.
To understand what distortion does to effect the amplified signal, has been shown that higher order harmonics are MUCH more annoying, than 2'nd or 3'rd harmonic. In fact, 7th harmonic is pretty much intolerable, and makes music sound, metallic. This might be OK with some musical instruments, but you don't want human voices to be changed in that way, normally. There have been several weighting curves put forth over the decades to more accurately predict distortion detection, but none, to my knowledge, is built into test equipment, where it might be useful.
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Old 20th May 2010, 07:31 AM   #4380
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Quote:
Originally Posted by QSerraTico_Tico View Post
Play one direct to disc LP on a good set and you have the answer....
Awesome!
Nice but not useful comment. Vinyl has many distortions. I don't think we can infer from this that adding those distortions is the way forward. I have access to direct to disk recordings, master tapes and high resolution digital. I can't say that any of them are a shining beacon illuminating the direction of the future. However I do seem to get the most satisfaction from the high resolution digital when well done. However this doesn't answer any of the questions I asked.
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