Guessing or estimating is not listening. Fuses are NONLINEAR and it is difficult to measure this nonlinearity properly, because the music can be so dynamic, yet the test equipment tones are so static. If you were to plot the resistance of a fuse from 1A to 10A, for example, then created an equation showing the nonlinearity, you might have an indication of the fuse problem. However, even this will remove the time constant element in the nonlinearity, and not be completely accurate.
Easy experiment take a simple G=100 in-amp circuit run on +9V batteries and measure the spectra of the fuse voltage with real and loud music playing. If the fuse is in the rail just connect common to the rail.
I'm surprised sometimes by the lack of experimental curiosity around some places.
I'm surprised sometimes by the lack of experimental curiosity around some places.
Amplifier behaviour dependence to fuse (yes-no, exchange for different type) is strongly topology dependent, so do not blame so much on fuses, rather blame it on circuit design. And, consider actual value of their non-linear resistance.
john curl said:
But if you look at the worst case drop across the fuse, and from that look at the ratio of signal to 'fuse ripple' it doesn't matter how non-linear the fuse is. You would have found the worst case situation as far as the magnitude signal contamination is concerned.
The non-linearity of the fuse would probably generate harmonics of the supply current on the supply line. That's a good point. Could these harmonics be larger than the 'carrier'? Probably not.
Jan Didden
scott wurcer said:
Good point.
I just did a few measurements on the amp I am currently working on http://www.diyaudio.com/forums/showthread.php?postid=1575583#post1575583 by inserting a 6A fuse (no name 5x20mm glass tube, got them in bulk from a junk store) on each power line (+/- 53V taken from a couple of DLM60-10 power supplies). I am estimating the amp PSRR at about -60dB @ 10Hz and -73dB @ 20KHz.
The DLM60-10 power supply has remote sense inputs. Rather than measuring the THD with and without the fuses I moved the remote sense(s) before/after the fuse(s). Of course, with the remote sense connected after the fuses, the PS loop gain linearizes any nonlinearity induced by the fuses.
My spectra equipment resolution is with high confidence and reproductibility around -130dB (limited by noise). The amp was set to deliver 200W in a 4ohm resistive load, that is an average current in each supply of 3.2A
Fed the amp with high purity (better than -105dB) 10Hz and 20KHz, notch filtered the fundamentals and measured the spectra with my HP3562A (photos available by request). The amp itself has about 10ppm (-100dB), substracted the before/after, with/without fuses spectra yada, yada, yada...
Results...
At 20KHz, jack s*it, diddly squat, zip, nada, nothing.
At 10Hz (unfortunately I can't go lower) there is a residual of about 0.5ppm (-126dB) 2nd harmonic which could be because of the fuses nonlinearities. More careful measurements would probably clear things up. Anyway, it's either my amp having a much better PSRR than the -60dB I am estimating or the fuse effect is, for all practical purposes, negligible.
Fuses you say?
I can't offer any insight into the effects of power supply or power cords on my preamp at all. That's because it has no active parts at all... passive it is. 😀
However, this book:
http://www.amazon.com/Loudspeaker-Headphone-Handbook-John-Borwick/dp/0240513711
...at least in the edition I read years back - from the public library don'tcha know - has or had a wonderful chapter on fuses, and their non-linearity.
Their angle is mostly WRT fuses in line with some sort of signal, like a speaker, but the measurements still hold.
Having said that, I've personally heard power cords, regulated supplies (similar but slightly different topology) make things that really ought not to, sound rather different to the ear (noticeably, not straining to hear some sort of differential) in phono stages, power amps, and DACs on a regular basis. So, it is difficult to lay it off to "improperly engineered" faults. Otoh, I suppose that it is possible to build gear, or ought to be possible to build gear that is rather insensitive to these things - and that still sounds proper/good (therein is something of a rub...).
I'd really love to have the measurement capability that syn08 appears to have... would be sweet.
_-_-bear
<secret message> John, ya can get me on the weekends!!
I can't offer any insight into the effects of power supply or power cords on my preamp at all. That's because it has no active parts at all... passive it is. 😀
However, this book:
http://www.amazon.com/Loudspeaker-Headphone-Handbook-John-Borwick/dp/0240513711
...at least in the edition I read years back - from the public library don'tcha know - has or had a wonderful chapter on fuses, and their non-linearity.
Their angle is mostly WRT fuses in line with some sort of signal, like a speaker, but the measurements still hold.
Having said that, I've personally heard power cords, regulated supplies (similar but slightly different topology) make things that really ought not to, sound rather different to the ear (noticeably, not straining to hear some sort of differential) in phono stages, power amps, and DACs on a regular basis. So, it is difficult to lay it off to "improperly engineered" faults. Otoh, I suppose that it is possible to build gear, or ought to be possible to build gear that is rather insensitive to these things - and that still sounds proper/good (therein is something of a rub...).
I'd really love to have the measurement capability that syn08 appears to have... would be sweet.
_-_-bear
<secret message> John, ya can get me on the weekends!!
Re: Fuses you say?
Mind you, I would not even think of attempting to protect the speaker by using a series fuse outside the FB loop. That would be 100% audible and definitely would not improve the sound 😀
It's the amp PSRR that greatly reduces the power line fuses effect. Now, I have seen commercial power amps (nomina odiosa!) with less than 35dB of PSRR. But then such amps have -60dB distortions anyway, so the effect of the fuses is still relatively still zero.
bear said:
Mind you, I would not even think of attempting to protect the speaker by using a series fuse outside the FB loop. That would be 100% audible and definitely would not improve the sound 😀
It's the amp PSRR that greatly reduces the power line fuses effect. Now, I have seen commercial power amps (nomina odiosa!) with less than 35dB of PSRR. But then such amps have -60dB distortions anyway, so the effect of the fuses is still relatively still zero.
Since I enjoy getting slagged once in a while, I'll add this inflammatory thought.
Engineering is a practiced discipline. One of the key ingredients to that is the use of simplifications and generally accepted assumptions. The final result is the product of a bunch of compromises and is never the "exact" solution. That's even presuming that the exact problem is fully defined and that the exact solution could be identified if it came and bit you in the butt.
How's this apply here? My observation is that most audio equipment is designed as an island, with little thought to the entire system. By that, I don't just mean the signal levels and impedances, although those are often just given passing thought. I'm thinking more of things like EMI, power system interactions, mechanical feedback, and so on.
As an example, people routinely discuss in rabid terms about the effects of power cords. Put aside your already established conclusions on this for a second. Why could these effects exist? The answer is that the problem is not just one of a microprocessor based lava lamp pouring noise pulses onto the line. A read through Ott's book on system noise actually discusses issues like this. That's not some exotic treatise done by some guy pushing an audio product for profit. The analysis doesn't require solving high order differential equations, either. More like what is taught (or at least used to be taught) in the very first electrical engineering course.
So, why is this kind of thing just ignored? If someone says that they hear a difference in sound when changing a power cord, that guy might be imagining things. But when several hear it, why not investigate how or why such a thing might be possible before dismissing it as a hallucination?
Sorry to stick with power cords, but that one has come up lately.
Engineering is a practiced discipline. One of the key ingredients to that is the use of simplifications and generally accepted assumptions. The final result is the product of a bunch of compromises and is never the "exact" solution. That's even presuming that the exact problem is fully defined and that the exact solution could be identified if it came and bit you in the butt.
How's this apply here? My observation is that most audio equipment is designed as an island, with little thought to the entire system. By that, I don't just mean the signal levels and impedances, although those are often just given passing thought. I'm thinking more of things like EMI, power system interactions, mechanical feedback, and so on.
As an example, people routinely discuss in rabid terms about the effects of power cords. Put aside your already established conclusions on this for a second. Why could these effects exist? The answer is that the problem is not just one of a microprocessor based lava lamp pouring noise pulses onto the line. A read through Ott's book on system noise actually discusses issues like this. That's not some exotic treatise done by some guy pushing an audio product for profit. The analysis doesn't require solving high order differential equations, either. More like what is taught (or at least used to be taught) in the very first electrical engineering course.
So, why is this kind of thing just ignored? If someone says that they hear a difference in sound when changing a power cord, that guy might be imagining things. But when several hear it, why not investigate how or why such a thing might be possible before dismissing it as a hallucination?
Sorry to stick with power cords, but that one has come up lately.
CG said:
And this is precisely why blind testing techniques were invented. To which the GEB (Golden Ear Brigade) systematically refuse to be subject of.
Me an my friend saw with my home telescope LGM's (as in Little Green Men) on Jupiter's Io satellite, bathing in a methane pool. Care to verify my assertion?
Ever thought that the GEB reason to exist is a desperate need to make a difference. For various reasons, starting from very low to very high on the Hierarchy of Need. Interesting enough, perhaps over 90% of the GEB members are not swindles but, unfortunately, a statistically significant percentage are. And don't fool yourself, it's not happening in the Audio field only.
syn08,
I'm not suggesting that there is a problem with fuses in the AC mains line - only pointing out that fuses have known issues that are reasonably well documented.
Should you use a fuse in the AC mains?
Seems necessary to use something for safety - take your pick of alternative means.
I can not say that I have ever heard the effect of a fuse in the mains of a power amp, fwiw.
As far a DBTs and ABX, this isn't the place to discuss that. I'll just say that all tests have their place and application(s), nothing more.
However it remains interesting that everyone here seems to be interested in peeling back the layers of the design "onion" seeking to squeeze out just a tad better performance - why? Does it really matter if one shunt regulator has a fraction of a percent less noise? Or if one resistor in John's line stage is 20 ohms or 50 ohms? Does it matter if you use a Vishay bulk film or just a chinese metal film? Do we really need to care about the thermal effects on those FETs? Does it matter which VAS stage works best with which driver/output combination? Etc? Is this all merely an exercise in mental gymnastics because we can, and/or have the training to do it? I guess the flip side of the same question is why isn't what exists already as done, finished and/or commercialized designs more than adequate?
At the risk of answering my own somewhat rhetorical question, to me it registers more or less like setting up a race car as compared to buying a Cadillac and driving it. One is more or less general purpose, the other is more or less very specific to the application & conditions (ie. specific to the audio system it is used in) and requires great attention to subtle details.
Putting the spin on it from the driver's point of view, a top pro race driver is exquisitely sensitive to extremely small changes in his ride - Consumer Reports or Car & Driver, not very sensitive.
_-_-bear
I'm not suggesting that there is a problem with fuses in the AC mains line - only pointing out that fuses have known issues that are reasonably well documented.
Should you use a fuse in the AC mains?
Seems necessary to use something for safety - take your pick of alternative means.
I can not say that I have ever heard the effect of a fuse in the mains of a power amp, fwiw.
As far a DBTs and ABX, this isn't the place to discuss that. I'll just say that all tests have their place and application(s), nothing more.
However it remains interesting that everyone here seems to be interested in peeling back the layers of the design "onion" seeking to squeeze out just a tad better performance - why? Does it really matter if one shunt regulator has a fraction of a percent less noise? Or if one resistor in John's line stage is 20 ohms or 50 ohms? Does it matter if you use a Vishay bulk film or just a chinese metal film? Do we really need to care about the thermal effects on those FETs? Does it matter which VAS stage works best with which driver/output combination? Etc? Is this all merely an exercise in mental gymnastics because we can, and/or have the training to do it? I guess the flip side of the same question is why isn't what exists already as done, finished and/or commercialized designs more than adequate?
At the risk of answering my own somewhat rhetorical question, to me it registers more or less like setting up a race car as compared to buying a Cadillac and driving it. One is more or less general purpose, the other is more or less very specific to the application & conditions (ie. specific to the audio system it is used in) and requires great attention to subtle details.
Putting the spin on it from the driver's point of view, a top pro race driver is exquisitely sensitive to extremely small changes in his ride - Consumer Reports or Car & Driver, not very sensitive.
_-_-bear
Y'know, I understand that there are frauds, con men, and all sorts of nefarious behavior surrounding everybody in every country on the planet. It's not very smart to ignore that, or to blindly accept anything and everything that people might tell you. But, I guess there's at least two ways to look at things.
One is to try to disprove everything that comes along. Or most everything. The reasons why people find that desirable or necessary probably are as varied as the number of individuals. That sure gets around the possibility of being defrauded.
A second is to actually investigate things to see if there is any validity, and then decide whether there is something to the idea or not. If it makes sense to you then go for it.
What I have often found is that many people who make observations, no matter how outlandish, may have made perfectly good observations for the circumstances. But, they get themselves into big trouble and often ruin their own observations by offering explanations that don't make sense or are inaccurate.
I myself am not especially on a crusade to prove that somebody is a fraud. If I think they are, I will tell somebody if they ask my opinion. But since this is a hobby, I don't imagine that the world will end or anybody's life will be diminished if they prefer to listen to their music sitting on a special pumpkin. For all I know, it just really might be better for them. But, if I don't find any value for me, I move on. My own interest is to see what I can do to enhance my own enjoyment of listening to music and the aspects of the hobby I find important.
Blind testing has its place, but the people I have spoken to outside the audio realm who make their career partly due to the DBT (medical researchers and the like) have always asked me what the objective measurement is for the results. For example, in testing a treatment for hypertension the results are primarily based on measuring blood pressure using some kind of calibrated apparatus. The testers don't base the results by asking the subjects, "Do you think your blood pressure is lower now since taking the treatment? Tell me which is better - pill A or pill B." That tests the measuring device as much as the treatment. With certain types of treatments for issues with the brain and behavior, for example depression, that really is the way the tests may have to be done. But the wide variety of individual results in that area suggests, at least to me, that without objective measurement tools, the results will vary with the individual. Just like audio DBT's. But, I just have to go by what these people, who are generally considered knowledgeable in that field, have explained to me. I sure don't know...
BTW, I don't have the means to verify your discovery of little green men on Io or in Montana, for that matter. But, I've heard that there are scientific programs looking to explore these very kinds of subjects. They're usually sponsored by various governments. I guess your point in bringing that up is to show that you can't believe everything anybody claims. That's very true, but that example does not prove that everything that everybody claims is wrong, either.
Please note: I have no connection to the audio business on any level, except as an occasional customer. Heck, based on the dollars spent, I'm not even a good customer.
One is to try to disprove everything that comes along. Or most everything. The reasons why people find that desirable or necessary probably are as varied as the number of individuals. That sure gets around the possibility of being defrauded.
A second is to actually investigate things to see if there is any validity, and then decide whether there is something to the idea or not. If it makes sense to you then go for it.
What I have often found is that many people who make observations, no matter how outlandish, may have made perfectly good observations for the circumstances. But, they get themselves into big trouble and often ruin their own observations by offering explanations that don't make sense or are inaccurate.
I myself am not especially on a crusade to prove that somebody is a fraud. If I think they are, I will tell somebody if they ask my opinion. But since this is a hobby, I don't imagine that the world will end or anybody's life will be diminished if they prefer to listen to their music sitting on a special pumpkin. For all I know, it just really might be better for them. But, if I don't find any value for me, I move on. My own interest is to see what I can do to enhance my own enjoyment of listening to music and the aspects of the hobby I find important.
Blind testing has its place, but the people I have spoken to outside the audio realm who make their career partly due to the DBT (medical researchers and the like) have always asked me what the objective measurement is for the results. For example, in testing a treatment for hypertension the results are primarily based on measuring blood pressure using some kind of calibrated apparatus. The testers don't base the results by asking the subjects, "Do you think your blood pressure is lower now since taking the treatment? Tell me which is better - pill A or pill B." That tests the measuring device as much as the treatment. With certain types of treatments for issues with the brain and behavior, for example depression, that really is the way the tests may have to be done. But the wide variety of individual results in that area suggests, at least to me, that without objective measurement tools, the results will vary with the individual. Just like audio DBT's. But, I just have to go by what these people, who are generally considered knowledgeable in that field, have explained to me. I sure don't know...
BTW, I don't have the means to verify your discovery of little green men on Io or in Montana, for that matter. But, I've heard that there are scientific programs looking to explore these very kinds of subjects. They're usually sponsored by various governments. I guess your point in bringing that up is to show that you can't believe everything anybody claims. That's very true, but that example does not prove that everything that everybody claims is wrong, either.
Please note: I have no connection to the audio business on any level, except as an occasional customer. Heck, based on the dollars spent, I'm not even a good customer.
scott wurcer said:
Any indication of this gets blown off as unprofessional and unscientific enough for the high tech tone displayed here...
Years ago... Swapped out copper tubing for fuses in rails in a then familiar power amp. Sounded better. Note to self: Fuses suck, stick with mains fuses to not burn house down.
Preamp: stick with mains fuses to not burn up good sounding power transformer.
Seems so simple. Now a daze's this logic is stupid. I guess a simulation would have told me my ears suck!
Talking about things will take you only so far. This is DIY Audio folks. Step away from the computer, turn on the soldering iron.
Ask me if I care? I find it hard not to comment sometimes.
Fuses prevent fires they are good.
There are definite and measureable limits to human hearing, but there seems to be no limits to the experiences that the brain can provide whilst listening to HiFi.
If our ears are the limiting factor there must be a point where it is pointless to continue improving the hardware.
Where does the measured performance of today's High End products stand?
Are we there yet?
Are the problems we hear in the gear or in our heads?
There are definite and measureable limits to human hearing, but there seems to be no limits to the experiences that the brain can provide whilst listening to HiFi.
If our ears are the limiting factor there must be a point where it is pointless to continue improving the hardware.
Where does the measured performance of today's High End products stand?
Are we there yet?
Are the problems we hear in the gear or in our heads?
People who question whether they hear audio improvements or not, should probably refrain from commenting on people who do. It would be like me criticizing SY or Scott W. for liking and comparing fine wine. I don't find the difference worth the price, but they do. Do I comment about them about the potential waste of money, and demand that they submit themselves to double blind testing, or revert to three buck chuck? 
john curl said:Do I comment about them about the potential waste of money, and demand that they submit themselves to double blind testing, or revert to three buck chuck?
I don't think most wine fanciers would put up a concerted, blinkered, career-long protest against DB testing.
I did my share of DB (ABX) testing starting 30 years ago. I came to the conclusion that it is worthless. If you feel differently, do your own tests, waste your own time, not mine.
Not today. Although blind tests have been advertised in autos. Remember Mercedes vs Mercury, anyone? About as useful as audio tests.
IMHO we have a way to go before any further improvement in sound reproduction becomes irrelevant. My ears are not confused between live and recorded. I have a pretty nice system, quite pricey, but the distinction between live and reproduced is obvious.john curl said:
The system does a good job on solo instruments, even trios, but give it a symphony and all doubt will be removed.
1. Volume, regardless of watts or xmax ratings, I've yet to hear a speaker (or system) that can reproduce the purity and sheer volume of a live trumpet at close range.
2. Intermods(?), on complex recordings the systems I've heard still manage to muddle the collective sounds of large groups of live instruments or voices.
3. Dynamic range, were not there yet.
So I agree with John, keep trying. Improvements are not only possible, but given the improvement in the last couple of decades additional progress seems quite likely.
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