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post #631 of 637 Old 03-30-2014, 09:11 AM
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Even if we had correct stats, we have no idea how much capacitive reserves we have in any one amplifier.
Hmm, Service manuals are banned in Washington state? ;-)

Seriously the schematic will not give you the answer at all. It is like looking at a car and knowing its specs and telling me you know at any one instant what gas mileage I am getting.
The above seems to be very badly confused. A schematic shows what component parts and can easily be used to determine what capacitive reserves are in an amplifier.

Gas mileage is a result, not a component part so it is not relevant to the statement being corrected here.

The component parts of an amplifier are listed on the schematic. Usually the static voltage across the capacitor can also be discerned, so whether you define "Capacitive reserves" as being given in microfarads or joules, it can be determined from the amplifier's schematic.
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post #632 of 637 Old 03-30-2014, 09:15 AM
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I'm not sure what that means, but the methodology I used was to consult a standard reference, such as this one

http://en.wikipedia.org/wiki/Crest_factor
Thanks for running those stats Arny. Alas it gets us no closer to the answer. With respect to known waveforms and RMS values, you can mess with the parameters and waveform until you get your answer. As I mentioned, you can't do that with music as you don't know the actual value.

Recall that I started this discussion by showing a waveform and selecting one of its peaks -- the very thing we are discussing as to the strain on the power supply -- and showed that the computed value by Audition were wrong. I later said that I had left one of the important fixes as an exercise for the reader. Let me show the effect of that in these two demos. Here is a song with a segment of the waveform selected and stats for it:

i-67xkWDB-XL.png

I purposely placed the selection to the vertical scale on the right so that we can visually do the math. We see that the "average" value is computed as -23 dB. If we look at the scale on the right we see that none of the selected waveform dip below 9 db. So clearly that statistic is wrong. Remember that "RMS" value is supposed to be the average. In this case the waveform is all positive so the RMS value is simply the average of all of those numbers.

Now look at what you get when you correctly use the program:

i-L56DNC6-XL.png

Ah, our average is now -5.31 db which is much more reasonable. The peak is 3.63. So the crest factor is 1.68 db! That is even smaller than a sine wave which makes sense since our selected waveform is spending its time at high amplitudes instead of gracefully dipping to zero as sine wave does.

BTW, I can select a different segment and have it spit out basically the same value for both!

Net, net, the tool requires expertise to use. You cannot ignore such things as -infinity as the maximum signal level and still think you are getting reasonable output by cherry picking the number that matches your argument.

The above would appear be just another example of using obviously erroneous analyses to justify obviously erroneous conclusions. Of course data can be sliced and diced so that its analysis produces an irrelevant result. We've got a number of papers that give representative numbers for the crest factor of music, and none of the above correlates with them. Let's hear it for peer review!
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post #633 of 637 Old 03-30-2014, 10:47 AM
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The above would appear be just another example of using obviously erroneous analyses to justify obviously erroneous conclusions. Of course data can be sliced and diced so that its analysis produces an irrelevant result. We've got a number of papers that give representative numbers for the crest factor of music, and none of the above correlates with them. Let's hear it for peer review!
Thank you for your perspective but I am puzzled by what you are saying. I showed a real piece of music and its real peak. I explained how one set of statistics was correct and another that was not. The correct value showed a crest factor less than 2 db -- a far cry from 10 db number you said music load imposes on the amplifier.

I took your lead and used Audition for this analysis. As such, the numbers are not generated by me at all. I showed you the actual output of the program.

I love to see what papers you have on this topic as the one I post last night does not apply because it is relying on averages, not peaks:

i-hXHhzfT-L.png

Your amplifier doesn't peer into your music shelf to decide what to do next. It plays whatever instant voltage is in the track being played. If it runs out of juice in one of these peaks, it matters not that if it had averaged that with 40 CDs you are not playing, the level would be lower. Please read the paper including its summary to make sure you know how to use the results out of it. This is the abstract:

i-7GKntRf-XL.png

Our discussion and goal is to find out the instantaneous music crest factor because that is what causes clipping at that moment. The paper and their study is using *averages* which is fine for their application of determining speaker power ratings and such but is of no value to our current discussion.

I would be delighted to see authoritative data shows no music peak has crest factors less than 3 db. So by all means, please share the papers. smile.gif

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post #634 of 637 Old 03-30-2014, 12:04 PM
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Can't you guys meet up at a nice B&B for a weekend and discuss over tea and cucumber sandwiches?
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post #635 of 637 Old 03-30-2014, 05:34 PM
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The above would appear be just another example of using obviously erroneous analyses to justify obviously erroneous conclusions. Of course data can be sliced and diced so that its analysis produces an irrelevant result. We've got a number of papers that give representative numbers for the crest factor of music, and none of the above correlates with them. Let's hear it for peer review!
Thank you for your perspective but I am puzzled by what you are saying. I showed a real piece of music and its real peak. I explained how one set of statistics was correct and another that was not. The correct value showed a crest factor less than 2 db -- a far cry from 10 db number you said music load imposes on the amplifier.

I took your lead and used Audition for this analysis. As such, the numbers are not generated by me at all. I showed you the actual output of the program.

How long did it take to cherry pick the data before you obtained results that agreed with your previous erroneous claims? ;-)
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post #636 of 637 Old 03-30-2014, 07:28 PM
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How long did it take to cherry pick the data before you obtained results that agreed with your previous erroneous claims? ;-)
Ratman and I did it over afternoon tea. So maybe an an hour or two?

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post #637 of 637 Old 03-30-2014, 08:02 PM
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Can't you guys meet up at a nice B&B for a weekend and discuss over tea and cucumber sandwiches?

You buying the airplane ticket? You know where we live?

Besides you can't change someone's character that easily. There are people in this world who are constitutionally incapable of admitting any error.
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