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| AB-class amplifier schematic analysis & optimization |
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| Alex Nikitin:
--- Quote from: Zero999 on May 24, 2019, 11:01:42 am --- --- Quote from: Alex Nikitin on May 24, 2019, 10:23:12 am --- --- Quote from: Zero999 on May 24, 2019, 10:15:05 am ---I'm not sure what you're asking? Double blind tests are a the gold standard for determining whether anything is detectable or effective. If your LM7171 amplifier is audibly transparent i.e. doesn't distort the sound, the difference between it and any other amplifier which is also audibly transparent, should be undetectable when subject to a double blind test. --- End quote --- So, you can not provide a link to a statistically valid DBT with a positive result (meaning that there is a difference in the sound confirmed in the test) ? So, you have a "gold standard" with negative results only, don't you think it is funny? Cheers Alex --- End quote --- I still don't know what you're going on about. Please provide a more detailed explanation of what you're asking. --- End quote --- OK, let's go back to your earlier post: --- Quote from: Zero999 on May 24, 2019, 10:15:05 am ---I'm not sure what you're asking? Double blind tests are a the gold standard for determining whether anything is detectable or effective. If your LM7171 amplifier is audibly transparent i.e. doesn't distort the sound, the difference between it and any other amplifier which is also audibly transparent, should be undetectable when subject to a double blind test. --- End quote --- The DBT is a tool. To use any tool you should understand its capabilities and limitations, otherwise you can not trust the results. My question is very simple - could you provide an example of a statistically valid DBT with a positive result, i.e. where the difference between the sound from two pieces of equipment was registered. Clearly, if you have 50% distortion on one of the sources it should give a good positive result, but no one will bother with this kind of test. However unless we have examples of positive results it is not clear where the test sensitivity border line is. Saying that it is "industry standard", "gold standard" and such doesn't prove anything, it is only a convenient smoke screen. DBTs in audio are notoriously insensitive, that is why their use is essentially a biggest can of a snake oil in this industry, IMHO. Well, again, could you provide a link to an example of a statistically valid audio DBT with a positive result? Cheers Alex |
| ratatax:
I know your suggestions here may be using higher quality parts, but what about this one : http://www.ti.com/lit/ds/symlink/rc4580.pdf It's cheap, has some oomph to be used as a headphones amplifier, has low enough THD/noise... and the implementation seems dead easy. I'm a musician but I like when choices are made with measurable, scientific proofs, since audio as it is perceived by our ears is way too much subjective. Some opamps with thousand of V/uS slew rate and hundred of Mhz bandwidth may sound very good but I feel it's just unneeded complications (unneeded costs too), like you can buy a race car to drive at 30mph in a city...but WHY ? ;D |
| Zero999:
--- Quote from: Alex Nikitin on May 24, 2019, 12:09:33 pm --- --- Quote from: Zero999 on May 24, 2019, 11:01:42 am --- --- Quote from: Alex Nikitin on May 24, 2019, 10:23:12 am --- --- Quote from: Zero999 on May 24, 2019, 10:15:05 am ---I'm not sure what you're asking? Double blind tests are a the gold standard for determining whether anything is detectable or effective. If your LM7171 amplifier is audibly transparent i.e. doesn't distort the sound, the difference between it and any other amplifier which is also audibly transparent, should be undetectable when subject to a double blind test. --- End quote --- So, you can not provide a link to a statistically valid DBT with a positive result (meaning that there is a difference in the sound confirmed in the test) ? So, you have a "gold standard" with negative results only, don't you think it is funny? Cheers Alex --- End quote --- I still don't know what you're going on about. Please provide a more detailed explanation of what you're asking. --- End quote --- OK, let's go back to your earlier post: --- Quote from: Zero999 on May 24, 2019, 10:15:05 am ---I'm not sure what you're asking? Double blind tests are a the gold standard for determining whether anything is detectable or effective. If your LM7171 amplifier is audibly transparent i.e. doesn't distort the sound, the difference between it and any other amplifier which is also audibly transparent, should be undetectable when subject to a double blind test. --- End quote --- The DBT is a tool. To use any tool you should understand its capabilities and limitations, otherwise you can not trust the results. My question is very simple - could you provide an example of a statistically valid DBT with a positive result, i.e. where the difference between the sound from two pieces of equipment was registered. Clearly, if you have 50% distortion on one of the sources it should give a good positive result, but no one will bother with this kind of test. However unless we have examples of positive results it is not clear where the test sensitivity border line is. Saying that it is "industry standard", "gold standard" and such doesn't prove anything, it is only a convenient smoke screen. DBTs in audio are notoriously insensitive, that is why their use is essentially a biggest can of a snake oil in this industry, IMHO. Well, again, could you provide a link to an example of a statistically valid audio DBT with a positive result? Cheers Alex --- End quote --- Yes, a DBT is a tool. If the results are that no one can differentiate between two amplifiers, any better than chance, then the two amplifiers both sound the same. This is a scientific fact. If no one can tell the difference between the two amplifiers, then saying the they are sonically different is lying. The same is true of a quack claiming their new spiritual healing treatment cures cancer: without a DBT it's total lies. No doubt two amplifiers can sound different and will give a positive result when subject to a DBT. This is likely to be the case if the amplifiers are over-driven or genuinely do produce distortion in normal operation. Some people might like certain types of distortion, so keeping THD figures down isn't always the goal. The idea people can hear things which can't be measured is snake oil. It's true the human ear is more sensitive to some types of distortion than others, so THD figures alone aren't always that useful, but everything which is audible is measurable and is the whole point in having expensive test equipment. No doubt tests have been done to determine what level of distortion is audible, tolerable, and immediately noticeable, in order to develop efficient lossy audio compression algorithms and determine the bare minimum standard for an audible transparent audio amplifier. To answer the question: no, I've not seen an example statistically valid DBT with a positive result, comparing two amplifiers, but that doesn't mean to say that DBTs aren't valid. It most likely means that all decent amplifiers quality sound the same, as long as they're operated within their specifications. I have watched Youtube videos demonstrating what levels of THD, of different types of distortion, people can hear and it would be interesting to see some more scientific DBTs. |
| Alex Nikitin:
--- Quote from: Zero999 on May 24, 2019, 12:57:17 pm ---Yes, a DBT is a tool. If the results are that no one can differentiate between two amplifiers, any better than chance, then the two amplifiers both sound the same. This is a scientific fact. If no one can tell the difference between the two amplifiers, then saying the they are sonically different is lying. The same is true of a quack claiming their new spiritual healing treatment cures cancer: without a DBT it's total lies. No doubt two amplifiers can sound different and will give a positive result when subject to a DBT. This is likely to be the case if the amplifiers are over-driven or genuinely do produce distortion in normal operation. Some people might like certain types of distortion, so keeping THD figures down isn't always the goal. The idea people can hear things which can't be measured is snake oil. It's true the human ear is more sensitive to some types of distortion than others, so THD figures alone aren't always that useful, but everything which is audible is measurable and is the whole point in having expensive test equipment. No doubt tests have been done to determine what level of distortion is audible, tolerable, and immediately noticeable, in order to develop efficient lossy audio compression algorithms and determine the bare minimum standard for an audible transparent audio amplifier. --- End quote --- 1) Please note that you "have no doubts" but you couldn't provide even a single link, only generic blah-blah. You should try to find an example I asked for, you might be in for a surprise. 2) Nowhere I said that "people can hear things which can't be measured" , that is you putting words in my mouth ;) , and I disagree with this idea. I like measuring things, moreover, my background in electronics is in the test and measurement :) . Cheers Alex P.S. --- Quote from: Zero999 on May 24, 2019, 12:57:17 pm ---To answer the question: no, I've not seen an example statistically valid DBT with a positive result, comparing two amplifiers, but that doesn't mean to say that DBTs aren't valid. It most likely means that all decent amplifiers quality sound the same, as long as they're operated within their specifications. --- End quote --- And that is not science, but a pure act of faith ::) . |
| dietert1:
Can't you just continue that discussion in private communication? I am afraid you are trolling this thread with your audiophoolisms. Regards, Dieter |
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