I think there are also unanswered properties regarding audio equipment such as "burn in", one side of me says that a component should perform the same initially as it would after 200 hours.
I saw once a test of capacitors and the graph showed a new capacitor and then the same capacitor after a week of use and the curve although the same was smoother, it initially it had some small bumps in it and after "burn in" the bumps were gone.
Smoke and mirrors, maybe or are there some things we don't yet understand?
I have found that gain plays a major part in the performance of an op amp and I am of the school that higher gain is better for op amps like the AD797 and LME49990.
Also switching out op amps may improve performance in respect to stability, an unsuitable op amp may be changed to one that is more stable in a certain circuit which would give better performance. The AD797 is known for it's instability if the circuit isn't right.
People were having problems with the LME49990 in the CNC phono stage, with overheating, they reduced the voltage to help alleviate this, however as I pointed out there must be something wrong, ie oscillations, I suggested a ceramic cap between the supply rail legs of the op amp and this seemed to cure the overheating problem.
Thanks for the reply!
1- To me, it makes no sense to ask if component "burn in" exists per se, because there is absolutely no reason to believe that any two different components will have the same behavior. Also, what are the initial conditions? What is "break in" and what is drift? What are the thresholds of the definition? The question needs a much better statement to be answerable.
2- However, the existence of "burn in" is a very trivial thing to test for. It isn't mysterious or difficult in the least! In fact, it has been tested ad infinitum and continues to be tested every day. How else do you think a manufacturer does Quality Control on the production line, measures performance to assure that it will stay the same for the customer, and is always pulling samples off the line for detailed life testing? Besides, audio is but one blip. Many industries would consider break-in effects a big problem. So, if any component shows any unexpected break-in effects, they are thrown away and redesigned. If there is unavoidable break-in, then the manufacturer exercises the parts appropriately.
3- Your gain comment confuses me. Why is higher gain "better" and in what particular circuit? What is the magnitude of the effect, etc?
4- Re, the ceramic cap solution... glad you found that solution. But, I find it facepalmingly comical that those folks in the first place would set out to change the op amps in a piece of equipment without using a scope to watch for oscillation, and half a dozen other potential issues. I mean, that would be like tweaking your car engine without a tach or speedometer. Worse, actually, since you can't see or hear electrons.
5- You touch upon a profound aspect, which I would love to discuss, but not tonight. Too tired! It's important not to confuse well-defined scientific facts, with a clear statement, premise and answer sample space, with extremely complex multidimensional questions. Such questions are often highly under-defined, or subjective/perceptual, and are not generally prone to specific answers.
Just because audio is full of many important questions of this later type, doesn't mean that the more specific facts we know of the former type or wrong or irrelevant. It just means that the complex questions must be treated very differently. Here are some examples of what I mean by "facts" vs. "questions":
Examples of "Facts":
"The Fourier Transform 100% fully characterizes a signal." or
"These two sounds are completely identical." or
"A human's perception of sound is not in any way affected by spectral content above 25 KHz, provided it is below the threshold of pain." or
"Listener #5 can distinguish between two amplifiers 82% of the time." or
"Localization Inter-aural Time Difference cues are decoded by a neural cross-correlater in the Medial Superior Olive of the brainstem."
Examples of "Questions":
"Why does Speaker A sound so much better than Speaker B when their specs are almost identical?" or
"Does Class A sound better than Class D?" or
"Have speakers gotten better over the last 40 years?" or
"What is the best sounding op amp?"
-k
