Jan and Pavel got it- I specified that I did all my measurements at the corner frequency, otherwise there's a different voltage across the cap combination. So you can either change the load or change the frequency when comparing series to parallel; I changed the frequency. This is why, I believe, John got erroneous results.
Exactly. That's why I did a midband measurement as a check, and only saw generator residual. The corner frequencies in my test are 24 and 96 Hz, which are unrealistically high for the purposes of seeing distortion.
Exactly. That's why I did a midband measurement as a check, and only saw generator residual. The corner frequencies in my test are 24 and 96 Hz, which are unrealistically high for the purposes of seeing distortion.
People ought to have to pass an exam before they are allowed to buy test equipment. Topics should include:
- if you changed the apparatus you changed the experiment
- a number on a meter is raw data, not a measurement - to get a measurement you have to apply the correct theory
- owning a 4 digit meter does not mean you can always measure things to 4 digits
- if you are comparing two things make sure they are the same in all respects apart from the thing you are interested in (or know how to calculate for the difference)
- a simulation is not a measurement
- if you changed the apparatus you changed the experiment
- a number on a meter is raw data, not a measurement - to get a measurement you have to apply the correct theory
- owning a 4 digit meter does not mean you can always measure things to 4 digits
- if you are comparing two things make sure they are the same in all respects apart from the thing you are interested in (or know how to calculate for the difference)
- a simulation is not a measurement
Well, why not to keep close to what we should do in real life ? I mean, we gone chose capacitance values for the same FC (to do not change the response curve of our circuit), and keep voltage and impedance of the source equal as well as load (because it is those of our circuit).
So, i would had changed the capacitances values between // and serial, instead. (Same brand)
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If you use different caps then you have changed the DUT. You would then have to test a number of caps to look for sample variation.Esperado said:
Changing the frequency is simpler, but you would need to know that the sig gen (and the rest of the apparatus) is equally well-behaved at both frequencies. So doing it either way brings snags - real life experiments are like that.
The one thing you should not do is simply change the total capacitance by 4 and then carry on regardless. That is a schoolboy sort of error.
Of course, that's something controlled. Changing the DUTs and trying to find significance, well...
Interesting discussion re CD audio and statistical analysis of sample values revealing errors in AD process and mastering.
Audio CD - A Health Check!
Anybody know of a Windows equivalent to the !CD_HealthCheck freeware listed on Audio Misc Software ?.
Dan.
Audio CD - A Health Check!
Anybody know of a Windows equivalent to the !CD_HealthCheck freeware listed on Audio Misc Software ?.
Dan.
I can recognize the "out of reality" objectivists symptom. While i love theory, I'm only involved in practical circumstances. 😉
I don't build caps. But, as i buy them, I'm interested in the price too. Part of the game.
And, yes, if you are involved in industrial process, you have to care of sample variations.
In this simple circumstance, the question could be (for me) "What is the best solution to minimize distortion, using a given value of final capacitance between 3 set-ups: 2 caps in Serial, 2 caps in parallel or only one." It seems to me it make sens.
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I think Lipshitz et al did this in the 80's. It's just a histogram of the data, you could do this in a few lines of Python.
So we remain adamant, no revisiting or reexamining of the past? I guess it's a waste of time.
BTW relying on the the listeners description of DA might as well be lead wires sound dull and heavy while silver wire sounds bright.
Silver wire, especially silver plated one, do sound bright to me. Am I the only one who thinks this?
[ducking] 😀
Gooooooood morning, DIY'ers !!
This is great. Everyone is doing a retake on all the tests over again. I put up W.Jungs writing on the subject and his conclusions so that Se and others who have been say it was I who did this on thd or promoted DA can read for them selves who said and did what.. along with the tests done. I would be esp interested in any other interpretation of Jung/JC test.
To this day, I have not done any THD tests... even though I have the equipment now.
But, now others are interested again....I have still some NOS on polar and tant and new also to compare any improvements over time.
We all know that the formulas for electrolytics have changed .... allowing for higher values in smaller size and higher voltage in smaller size while keeping reliability more or less constant. So, if any of you have NOS..... check them against new fresh parts also. leave no rock unturned. You might want to properly reform them.... test before and after, also.
You have my full support.
THx-RNMarsh
This is great. Everyone is doing a retake on all the tests over again. I put up W.Jungs writing on the subject and his conclusions so that Se and others who have been say it was I who did this on thd or promoted DA can read for them selves who said and did what.. along with the tests done. I would be esp interested in any other interpretation of Jung/JC test.
To this day, I have not done any THD tests... even though I have the equipment now.
But, now others are interested again....I have still some NOS on polar and tant and new also to compare any improvements over time.
We all know that the formulas for electrolytics have changed .... allowing for higher values in smaller size and higher voltage in smaller size while keeping reliability more or less constant. So, if any of you have NOS..... check them against new fresh parts also. leave no rock unturned. You might want to properly reform them.... test before and after, also.
You have my full support.
THx-RNMarsh
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How many times will I need to repeat that:
This choice is debatable, but we have to find a fair way of making comparisons: if for example you are allowed to connect in series an indefinite series of capacitors, you will probably achieve a very low THD, but it will require a large volume if want to keep the same corner frequency
I have used spice only to illustrate the setup and indicate the voltages applied to the capacitors, not for the actual measurements
See above: I physically measured real parts, but used LTspice to present the results
Unlikely: people make errors, if you see what I mean....
No sim, pure measurements in my case
First task: find a fair way of comparing different setups: simply saying, we apply a constant voltage across the composite cap is certainly not one: you are going to change the corner frequency, and the composite arrangements will be bulkier than a single cap.
The value of the caps could be changed depending on the configuration, but that is certainly not a good solution, because we want to use the same caps throughout (different caps could have different behaviors).
Here is what I propose to (sensibly) normalize the setups and conditions with identical caps:
-The single cap is the reference: its C*V (4µ7*35V) value is one unit. The normalized corner frequency is also one unit.
-The series composite has two CV units and two frequency units. To make a fair comparison (same volume for the same corner frequency), the voltage across the composite has to be corrected by a 2*2 factor = 4
-The parallel composite also has two CV units, but 0.5 frequency unit, resulting in a 1 correcting factor wrt the single cap. This configuration is disadvantageous though, because it has zero additional DC blocking capability.
Maybe this necessitates some kind of penalty?
I don't know, this has to be discussed, in the mean time, I will make new measurements taking into account the above weighting system
I am going to create a dedicated thread on this subject, because debating in the mud-hole that this thread has become is not practical...
See here:
http://www.diyaudio.com/forums/parts/273799-non-linearity-polar-caps-arrangements.html#post4313188
Elvee, if you ground the caps and the R on top, what is then the result? That could be compared to Pavel's.
Secondly, I am not an LTspice experts but V(2,2) looks odd to me - but I may be totally wrong here. Just flagging it.
Jan
Secondly, I am not an LTspice experts but V(2,2) looks odd to me - but I may be totally wrong here. Just flagging it.
Jan
Let's not sink into noise by omitting basics. LTSpice works OK and gives same results as MicroCap. The problem is not in LTSpice.
You still don't get it, your, Walt's and John's DA measurements are just fine it's just that in the exact application context the errors are trivial. Frankly after all these years I thought you guys were fussing over .02dB deviations from RIAA, I didn't know any better.
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And observing a waveform using a scope probe can influence the waveform. especially as frequency goes up..... you can model the scope probe within a sim so you get the real waveform, I should imagine at audio frequencies the effect would be minimal...
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