SY beat me in a reply to this. I should thus shut up - only these arguments keep recurring ....
Firstly there is the fixation with capacitors 'in the signal circuit'. I presume this stems from the pictorial impact of a circuit diagram - those coupling caps sitting there as essential 'bridges' for signal from input to output.
All capacitors are in the signal circuit. A.c. flows in a circle, thus the capacitors 'there' are not more important than the capacitors in the 'return' circuit (e.g. power supply filters, cathode and other bypass capacitors.)
Then (this is where SY scooped me) the characteristics of a coupling capacitor is relatively unimportant despite religious belief in the opposite. For any real or imaginary effect by the capacitor on the signal, there needs to be a signal (a.c.) across the capacitor. In the pass-band that condition does not exist; a coupling capacitor is simply a d.c. block (one presumes it is not leaking, vented or suffering from some other malady). Thus, as SY intimated, any 'distortion' caused by said capacitor will act according to the ratio of the signal across it to the existing signal in the circuit. This is mostly way below other distortion products of the instrument, unless the design is so catastrophically ill-conceived that it merits no discussion. (I once again refer to the landmark series on capacitor effects - four instalments I believe - by Cyril Bateman about 14 years ago. It is freely available on the internet and should be studied by all.)
As was said, capacitor impedance will come in at audio band extremities, but those fall (or should do so) outside the useful audible range of frequencies (unless again ....)
Some folks are emphatic regarding their personal experiences even to the dismissal of science - those who did have such. I respect that; I was not present at the occasion to criticise. I can only state that science is not democratic; it is not subject to personal sensory experiences by the majority (if that be the case; here it is not).
Firstly there is the fixation with capacitors 'in the signal circuit'. I presume this stems from the pictorial impact of a circuit diagram - those coupling caps sitting there as essential 'bridges' for signal from input to output.
All capacitors are in the signal circuit. A.c. flows in a circle, thus the capacitors 'there' are not more important than the capacitors in the 'return' circuit (e.g. power supply filters, cathode and other bypass capacitors.)
Then (this is where SY scooped me) the characteristics of a coupling capacitor is relatively unimportant despite religious belief in the opposite. For any real or imaginary effect by the capacitor on the signal, there needs to be a signal (a.c.) across the capacitor. In the pass-band that condition does not exist; a coupling capacitor is simply a d.c. block (one presumes it is not leaking, vented or suffering from some other malady). Thus, as SY intimated, any 'distortion' caused by said capacitor will act according to the ratio of the signal across it to the existing signal in the circuit. This is mostly way below other distortion products of the instrument, unless the design is so catastrophically ill-conceived that it merits no discussion. (I once again refer to the landmark series on capacitor effects - four instalments I believe - by Cyril Bateman about 14 years ago. It is freely available on the internet and should be studied by all.)
As was said, capacitor impedance will come in at audio band extremities, but those fall (or should do so) outside the useful audible range of frequencies (unless again ....)
Some folks are emphatic regarding their personal experiences even to the dismissal of science - those who did have such. I respect that; I was not present at the occasion to criticise. I can only state that science is not democratic; it is not subject to personal sensory experiences by the majority (if that be the case; here it is not).
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That's pretty much what I would have thought too. Having said which, I suppose one could imagine, though, that if a particular capacitor type (e.g. polyester) had more significant deviations from the idealised capacitor model (such as more non-linear distortion), then it might be capable of producing audible effects. As long as the discussion can be at the level of what is measurable, I am reasonably happy. (The articles that were cited by hollowstate were quite interesting. I found another quite nice article, at Measured Differences Between Capacitors for Audio Applications) But as SY was implying, and Johan Potgeiter has just reinforced too, the effects of any small capacitor deficiencies would become pretty minimal if the value chosen were sufficient to keep the ratio of the signal across the capacitor to the signal in the circuit small enough. But in any case these things can all be measured, and that should produce trustworthy and non-subjective answers.
It would be interesting, though, to know what kinds of capacitor are typically used in all the earlier stages of the audio path, over which the home end-user has no control. (Such as in the recording studio, etc., etc.) My guess would be that in general they would simply be following industry-standard practices, which would be unlikely to be particularly cognisant of audiophile preferences (which in any case can wildly differ from one person to another). So that does still leave me wondering: If the audio signal has, say, passed through 50 bog-standard capacitors on its way from the microphones to the output of the CD player, is there any reason why the nature of the relatively few capacitors in the home stereo amplifier would have a disproportionately significant effect on the final sound? Especially when one considers that probably the overwhelmingly largest contributor to linear and non-linear distortions in the entire chain will in any case be the loudspeakers. (Except, possibly, in the case of some SE tube amplifiers.)
Chris
Yes, see my current sig line...
Re: your discussion of measurement, do a loopback with a good soundcard. They almost invariably use electrolytic coupling caps. Guess what? Yep, as predicted, the distortion contribution is 67% of FA.
Modern designs based on surface-mount technology usually contain exclusively C0G ceramics and ordinary aluminium electrolytics. When plastic caps are occasionally necessary, they are usually something better than polyester (anything is better than polyester). However, many studios still use a great deal of vintage or vintage-clone equipment, which commonly does use polyester and cheap ceramics, and other less-than-desirable dielectrics. For example, part of the much-loved sound of some Neve equipment is the tantalum coupling caps 😱! Recording engineers are usually concerned with creating a sound, not preserving it.
The electrical engineer in me tells me that there are some reasons that certain TYPES of capacitors will affect the sound quality. Ceramic capacitors ALL have some piezoelectric properties, some far worse that others, Some plastic capacitors, and most electrolytics suffer from dielectric absorption....
Within reason a well constructed version of a given TYPE of capacitor should sound the same as another well constructed version of the same type and value.
As SY pointed out there should be no AUDIO voltage across a capacitor except possibly at frequency extremes where the capacitor's ESL or Xc begin to become a sizeable portion of the circuit's impedance.
A properly designed circuit will attempt to minimize the audio CURRENT through a coupling cap, and keep it constant across the audio frequency band. The typical coupling cap into the grid of an output tube may see a dropping impedance as the grid approaches zero volts, and therefore may exhibit less than ideal behavior. This is why I tend to avoid this situation in my amp designs, but is the reason that you should use a good quality cap in that position. The definition of "good quality" is of course subject to some debate.
I have been guilty of using a $5 cap in a high end amp. Does it sound better than a 50 cent cap?????? Would you buy a $1000 amplifier if it proudly displayed those 50 cent caps????
Within reason a well constructed version of a given TYPE of capacitor should sound the same as another well constructed version of the same type and value.
As SY pointed out there should be no AUDIO voltage across a capacitor except possibly at frequency extremes where the capacitor's ESL or Xc begin to become a sizeable portion of the circuit's impedance.
A properly designed circuit will attempt to minimize the audio CURRENT through a coupling cap, and keep it constant across the audio frequency band. The typical coupling cap into the grid of an output tube may see a dropping impedance as the grid approaches zero volts, and therefore may exhibit less than ideal behavior. This is why I tend to avoid this situation in my amp designs, but is the reason that you should use a good quality cap in that position. The definition of "good quality" is of course subject to some debate.
I have been guilty of using a $5 cap in a high end amp. Does it sound better than a 50 cent cap?????? Would you buy a $1000 amplifier if it proudly displayed those 50 cent caps????
if some of the capacitors in your guessing game comparison are the wrong type for the duty they have to perform, then you are almost guaranteed that performance will both measure differently and sound differently.
You MUST use and by implication compare the correct type of capacitor in the correct location.
An example.
Omit the local decoupling and force remotely located capacitors to double up on DC current supply and HF current supply and you are bound to hear and be able to measure differences in performance when one tries different capacitors.
That is because the design was flawed in omitting the local decoupling. The wrong type were used, i.e. none instead of an ultra low impedance at the point of HF current change.
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".the point is you have a preference...so there would have to be a difference."
I guess I have to admire your faith in your hearing...I have absolutely no faith in my own, and unless I could verify my "preference" under strict double-blind testing I would not believe my own ears at all.
A lot of the research in human perception has revealed that the brain is astonishingly adept at "filling in," extrapolating, and sometimes supressing, based on expectations, and it may well not be minutely analysing every nuance in a complex situation. (For example the classic optical illusions, such as the film clip where a man in a gorilla suit walks across during the middle of the clip, and the vast majority of the viewers don't notice him.) Hearing, or imagining, the difference between copper and steel wires, based maybe on some preconception, seems like a pretty fine detail compared with the gigantic "mistakes" the brain has been shown to make in much more basic examples.
Personally, I would believe almost nothing, unless it could be confirmed by measurable differences or else by rigorous double-blind tests.
Chris
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I find it quite comical,
No body has any faith in their hearing..so how do you pick a HIFI?
Look at the box and measurements and just take it home?
There is no point in listening to it if you are convinced the colour of the amp or box logo is going to effect what you hear.
Whats the point of HIFI anyway if you can't trust your self to pick a system! just buy a decent midfi it will measure well within hearing range.
I have never read such a load of tosh.. HIFI is to listen to..If you believe you can't hear a difference in any audio AND have some faith in you ability to hear then I'm sorry your just hypocrites. Whats the point of doing HIFI<<<just so you can pat yourself on the back with an improved curve/spec?
Regards
M. Gregg
No body has any faith in their hearing..so how do you pick a HIFI?
Look at the box and measurements and just take it home?
There is no point in listening to it if you are convinced the colour of the amp or box logo is going to effect what you hear.
Whats the point of HIFI anyway if you can't trust your self to pick a system! just buy a decent midfi it will measure well within hearing range.
I have never read such a load of tosh.. HIFI is to listen to..If you believe you can't hear a difference in any audio AND have some faith in you ability to hear then I'm sorry your just hypocrites. Whats the point of doing HIFI<<<just so you can pat yourself on the back with an improved curve/spec?
Regards
M. Gregg
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If a component change changes the sound, then at least one of those two components is wrong/faulty.
Eliminate the "wrong component" to get the equipment performing properly.
Eliminate the "wrong component" to get the equipment performing properly.
If some of you are saying there should be no change in sound w/ the change of a capacitor, then you've never tried swapping caps yourself! It's an obvious thing.. Nothing psychoacoustic.
There is no doubt replacing PIO w/ a film cap changes the sound.
Maybe you're saying PIO is the "wrong component" and I'd believe that.. In every amplifier, HIFI or guitar, SS or Tube, even in various synthesizers I've built, you can always hear a change from PIO to film caps of the same value.
-Want to add about the question of caps in the recording chain.. Listen to recording from different eras, and you can certainly hear the change in recording equipment. Older 40's and 50's recordings all have a sound that changed in the late 60's and 70's, and changed again in the 80's and 90's.. Basically, the errors of the technology of the day are all there, but we just accept them as the sound of the music we buy. We can't change that, so don't bother thinking about it.
There is no doubt replacing PIO w/ a film cap changes the sound.
Maybe you're saying PIO is the "wrong component" and I'd believe that.. In every amplifier, HIFI or guitar, SS or Tube, even in various synthesizers I've built, you can always hear a change from PIO to film caps of the same value.
-Want to add about the question of caps in the recording chain.. Listen to recording from different eras, and you can certainly hear the change in recording equipment. Older 40's and 50's recordings all have a sound that changed in the late 60's and 70's, and changed again in the 80's and 90's.. Basically, the errors of the technology of the day are all there, but we just accept them as the sound of the music we buy. We can't change that, so don't bother thinking about it.
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If you read more carefully what I was saying, you would see that my point was that I would not trust my ears if I could not either measure some difference that would be capable of accounting for the perceived sound difference, or else if I could confirm my perceptions in double blind tests.
So yes, I could imagine that there might be circumstances where a change of capacitor type could be capable of producing an audible change. Though, as I think SY and Johan Potgeiter were suggesting, this could quite likely be if too low a value was being used, meaning that there was too much audio signal across the capacitor in the first place.
My stance in all this is that claimed audible differences that lie beyond what is measurable or verifiable in blind tests are most likely to be imagined. I am not saying there could not in principle be audible differences.
Chris
Do "HiFi" vs "midfi" amps actually measure differently? (It's a real question.. I'm not familiar w/ the commercial scene, or even what the difference between hifi (Self built or very expensive) and midfi (good big box store product) really is 🙂 )
I would guess they don't....... Or even that 'midfi' measures better.. But I should shut up, because I don't know.
I would guess they don't....... Or even that 'midfi' measures better.. But I should shut up, because I don't know.
"It's an obvious thing.. Nothing psychoacoustic."
Good for you. Enjoy!
Just please don't design my airplane or heart monitor using those standards.
Good for you. Enjoy!
Just please don't design my airplane or heart monitor using those standards.
Maybe we need a vote to see who can hear the difference? Or maybe all the PIO caps I've ever encountered in my life have been flawed? Not sure, but I stand by my statement. It's obvious. I never said you could not measure it... I don't know.. I probably don't have the equipment.
(and for the record, I have successfully designed airplanes multiple times.. RC.. but still.. my designs fly beautifully. I'm not saying you shouldn't trust maths)
And answer my second question. I'd really like to know if high dollar or high time cost (when self built) amps actually measure BETTER than a decent mid-fi product you can go to a regular electronics store and buy.. From my limited experience, they don't. And in that case, why are you here and not at 'best buy' or whatever the equivalent is in your country? Personally I come from a very scientific background, and if the audio hobby has taught me anything, it is to question our test equipment.. Or to question whether we are actually testing for the correct things.
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Technical facts are not democratic. 😀
Because designing and building stuff is a fun hobby.
BAH, I can't argue w/ that 🙂
-I can't argue w/ either of those, and you've actually gotten me out of my bad monday morning mood w/ those answers 🙂...
DIYAudio is a great place.
-I can't argue w/ either of those, and you've actually gotten me out of my bad monday morning mood w/ those answers 🙂...
DIYAudio is a great place.
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IMO, we can measure differences far below what we can hear, so measurement makes a certain amount of sense. If there's no signal voltage across the cap, it can't affect the signal- now, not being a tube guru, and since it's the tube amp people that seem to claim the greatest sensitivity to cap differences, has anybody done the measurements across coupling caps in tube amps? Are the caps in fact large enough to minimize the voltage drop? Does stray capacitance get involved to any important degree?
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