I think that 'linear distortion' should be thought as a departure from the original path, as seen on an oscilloscope with a fat pulse, much like a phase shift circuit can seriously modify a square wave. In this case, however, the cap modifies the path of the audio waveform (or amplitude/time relationship in a big way. Up to 10% per cap, as we initially measured it.
In other words, we could get up to a 10% deviation with a SINGLE CAP from the path of an IDEAL CAP, without adding or subtracting harmonics or noise. Please think that through, even try a differential cap test, yourself.
In other words, we could get up to a 10% deviation with a SINGLE CAP from the path of an IDEAL CAP, without adding or subtracting harmonics or noise. Please think that through, even try a differential cap test, yourself.
anatech said:
At this moment the boys aren't even pretending to sleep, so I'm on-call for various "he hit me" complaints, not to mention the random bonked noses resulting from falls, etc.
Your post, like SY's, seems based on a sanitized, idealized version of science. Perhaps Canada, like California, is full of rational people without feelings or prejudices, but out here in the real world, people are still human and have emotions. Odd, that.
You make the same error that so many others have made. Take a random designer. He comes up with a circuit, builds some form of prototype, then does what? He tests it. Then and only then does he go to the listening room already knowing the results of the measurements. If this hypothetical designer is one of those who think THD is a total descriptor of sound quality, he has already fatally prejudiced the listening test before he even begins.
Of course it sounds better to him! It has lower distortion than its predecessor and he knows this before the first note is played!
You're telling me this isn't a powerful determinant in his assessment of the sound?
Get real, dude!
The 'listener bias' blade cuts both ways, Chris, and I don't see any attempt whatsoever to call measurements-oriented folks to task for their all-too-obvious prejudices.
I am in the midst of fiddling with a line stage. To date, all I've done is measure it. By definition, I already know the distortion measurements as they stand at this time. The difference being that I don't put much stock in them. Still, by the time I get the silly thing into my system to listen to it, that information will be in the back of my mind. Will it alter my perception of the sound (in either way)? Who knows? I don't think it will have much bearing because I don't feel that distortion specs mean much below a certain point (I've already got the circuit below the oft-cited .1% THD threshold, and that's with no feedback). John's solution may be better than mine, in that he says he designs, then lets others evaluate. I don't have that luxury, in that I'm virtually alone in this entire state, and don't know anyone whose hearing I trust, anyway. The last two fellows in that category moved away years ago.
But at least I am aware of and acknowledge the problem. Do you see any such admission from anyone else? Please give me links to posts by syn08, G.Kleinschmidt, and others of their ilk wherein they admit to this possibility.
No links? No surprise.
Do I 'disregard' what the measurements say? Depends on your point of view, I suppose. From my experience with tube gear, I'm comfortable with higher measured distortion than many here would consider permissible. That said, I try to get solid state stuff below .1% just to be on the safe side. Once there it's safe to say that I pretty much ignore the actual figures; they're of no more importance to me than whether the rails measure 32.0Vdc or 32.1Vdc. It's just a number.
You mention the ability and experience of those who measure, but imply by exclusion that listening-oriented people have none. Brilliant! Your bias is laid bare. You also ignore the history of audio (audibility of passive components, etc.), wherein it was the folks who listened who led the way, not the other way around. That inconvenient little truth always gets ignored. Note that it didn't take double blind tests and all that fol de rol to figure out that something was wrong with "pure, perfect sound forever." Nope, all it took was individuals saying, "I don't care what the specs claim, this just doesn't sound good." But time after time, people dismiss listeners out of hand because they aren't "scientific."
Yeah.
Right.
Chris, sometimes real world observations are science.
Your point about meter-readers accepting the uncertainty of their measurements is one of those things I had to read three times to verify that I saw what I thought I saw. Listeners don't accept uncertainty? What? Either life is really very, very different up there in Canada or you're delusional. In the last few pages of this thread, I've mentioned the VPI Magic Bricks that listeners embraced, then abandoned, and Bear brought up the Tice clocks, which shared a similar fate, and those failures were hardly unique. And your evidence for the 'uncertainty' of measurements-oriented folks is what? They've changed their stance on what, exactly?
Oh, puh-leeze!
This goes beyond the normal realm of misunderstanding or not choosing the proper word for the moment when posting. We've all done that from time to time. Some of these recent posts (yours as well as others) show an astonishing disconnect from reality.
You are (I'm guessing, forgive me if I'm wrong, but you indicate you were in retail during the right time period) old enough to remember the introduction of Red Book CD. You're also old enough to remember when people were criticized for claiming that there were differences in caps. You're old enough to have lived through a number of the events I've cited in my last few posts.
But you are not old enough--I hope--to claim Alzheimers as an excuse for not remembering.
It's this sort of revisionist history that I find troubling.
Grey
GRollins said:
Hi Grey,
This 'listener bias' can also have the opposite effect. Many times I have listened to very low distortion amps and loudspeakers as well. Most of the time it was a bit of disappointing experience: I heard nothing special. I wouldn't say dull, rather not really exciting.
So, when I have finally finished my sub ppm THD amp (next year?), I don't expect it will sound as a sonic miracle.
Regards,
Edmond.
decoupling caps
Hmm...when decoupling has to be effective in the (tens or hundreds of) megahertz range (power MOSFETs!), I wouldn't rely on polystyrene or other winded caps. I think that MLCs and other stacked capacitors are more appropriate.
Here some interesting links about caps:
http://www.cliftonlaboratories.com/capacitor_voltage_change.htm
http://www.cliftonlaboratories.com/bypassing.htm
http://sound.westhost.com/articles/capacitors.htm#7.0
Regards,
Edmond.
Sigurd Ruschkow said:
Hmm...when decoupling has to be effective in the (tens or hundreds of) megahertz range (power MOSFETs!), I wouldn't rely on polystyrene or other winded caps. I think that MLCs and other stacked capacitors are more appropriate.
Here some interesting links about caps:
http://www.cliftonlaboratories.com/capacitor_voltage_change.htm
http://www.cliftonlaboratories.com/bypassing.htm
http://sound.westhost.com/articles/capacitors.htm#7.0
Regards,
Edmond.
you think to much "audio"...
Impulsedistortion via lowpass is the most prominent and first encountered form of distortion in EE. It affected electrical communications from the beginning in telegraphy to nowadays digital transmissions.
regards
Juergen Knoop said:
Of course, but I prefer to call this "filtering" or "channel bandwidth effect" or "channel capacity effect" rather than "linear distortion".
For the particular case of audio and DiffMaker, you don't need to swap the cap type (ceramic/poly/etc...) to get "linear distortions". Just swap with an identical model and the value change due to cap tolerances will provide you with a nice, easily measurable, "linear distortion". Does this kind of measurement make any sense?
I remember discussions, where the posters stated that audible differences between caps vanished, if just the capacitance was closely matched.
So much for caps and hearsay...😀
regards
syn08 said:
No, it doesn't make much sense, I agree. But it still might be of interest to know if a cap causes only 'linear distortion' in this sense or also non-linear distortion.
It's just a matter of agreeing to the terminology. It does seem kind of accepted terminology.
Jan Didden
Juergen Knoop said:
Others also say +-.1dB equalization makes all cable differences vanish. 🙂
To be politically correct I will say that I have not bothered to verify this so I don't know.
janneman said:
Does DiffMaker have any provisions to distinguish between linear and nonlinear distortions? If not, how would you know you are dealing with caps tolerances (linear) vs. e.g. piezoelectric effects (nonlinear)?
Most here are incredibly far behind on understanding 'linear distortion' or cap differences. More than 25 years behind, to be sure. Also, hearsay evidence is used from mid-fi listeners, and stated as accurate and useful. Learn about what is already known. Then, if you don't care, at least you are not as ignorant as you are now, about cap differences. I would go to Walt Jung's website and read EVERYTHING about cap differences and cap testing, if I were you. Test on Monday!
syn08 said:
No, there isn't, and you don't know. I was not talking in relation to DiffMaker in my post.
Example:
/quote
Audibility of Linear Distortion with Variations in Sound Pressure Level and Group Delay
Recent psychoacoustic studies of nonlinear distortion have yielded some new insights into what audible problems in loudspeaker might be related to. This paper will show the results of recent subjective tests which extend the work of various previous works to show that sound level significantly affects the perception of linear distortion in audio systems. This means that the hearing system itself is nonlinear and what has been thought of as being nonlinear distortion in the audio system may actually be a nonlinear perception directly in the receiver itself.
/unquote
?
For the record, when we make cap difference tests, we match the RC time constant of 2 separate caps to within .001%, This is not easy, but it is possible over a short measuring interval of several seconds. This REMOVES any reasonable difference between the caps as far as value is concerned. We try NOT to make the ratio too large, because it might affect the Common Mode Ratio on the IN-AMP. We usually stay within 10:1 worst case and 1.2:1 optimum case. We change STANDARD (usually Teflon or polystyrene) caps to match the value of the cap under test, in order to keep the ratio low.
Dielectric Absorption has little or nothing to do with either level OR cap value.
Dielectric Absorption has little or nothing to do with either level OR cap value.
john curl said:
Anyone can do this test, it's very easy to set up. I did years ago but rarely did I find any actual distortion except using the worst possible components. BTW Jim William's just sent me his Wein bridge oscillator article and mentions that "any" reasonably good R's and C's will do 1ppm in this circuit. On a funny note I mentioned to Jim that the classic light bulb circuit can't actually work without some distortion in the amplifier, he sent me an article from HP (1960) confirming this, oh well 50yr. out of date.
andy_c said:
Correct, but I think he also noted that the process isn't perfect. So, when you hear a residue in a cap difference track, can you determine from listening to the difference whether it is linear or non-linear distortion? For instance, when you listen to the residue in the Z5U case?
Jan Didden
What you are most probably hearing is NON-LINEAR distortion. DA is there, BUT the non-linear component IN THIS CASE is more dominant. I first published this distortion in 1978 in an IEEE paper. Get up to speed, please.
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