KBK, your parallel fuse idea is interesting, but impractical for commercial designs. However, it perhaps does point out that fuses and fuse holders are very poor construction from an audio quality point of view. I would think that a circuit breaker would be more appropriate in most cases.
Personally, all that I want is quality audio. If I could do it with cheap, commercial parts, I would do so. In fact, I design lots of product that uses cheap, commercial parts, but I don't consider it my best effort, and listening tests will make this obvious to serious listeners. However, I put just as much effort in the DESIGN of the cheaper stuff, as I do with the expensive components, and it is much the same in basic design topology, even if I have to use IC op amps for the audio circuit path.
Personally, all that I want is quality audio. If I could do it with cheap, commercial parts, I would do so. In fact, I design lots of product that uses cheap, commercial parts, but I don't consider it my best effort, and listening tests will make this obvious to serious listeners. However, I put just as much effort in the DESIGN of the cheaper stuff, as I do with the expensive components, and it is much the same in basic design topology, even if I have to use IC op amps for the audio circuit path.
quote:
Originally posted by syn08
For the sake of this thread, your 30yrs experience is a handicap not an asset.
This is exactly the kind of attitude and self appointed " ME only Knows", that this and some other threads are full of, and which represents a level of silliness that is quite ridiculous, and also quite destructive in terms of exchange of ideas and knowledge.
First - I am not attacking anyone in persona, rather than the attitude of such opinions.
There is a rather strange phenomenon associated with "High End Audio", where a number of designers, some educated and some self thought, and very few are theoretically highly educated, - that the problems of High End are unique to this feld, and noone else in other fields of electronics has any clue at all to what's going on, - except the very same self appointed gurus, - or maybe an inner circle of the same.
This is, of course, not saying that some of these gurus have made some very successful designs, which some most certainly have.
Quite a lot of the content of this thread deals with grounding and shielding techniques, where in education, Ralph Morrisons " Grounding and Shielding Techniques in Instrumentation Design", first edition in the late 60s, is still the Bible, and being used in several colleges and universities all over. Sofar, I've seen nothing over the years to prove this Bible wrong! But of course, new materials and a other new tricks have been developed since then, and still are. There's just even longer in between them.
The assumption, that signal purity and noise control, is special to High End, is just another piece of rubbish thinking. Quite a number of topics in various fields of instrumentation deals with much smaller signals than High End Audio, and have exactly the same problems to combat, to an even higher degree than High End. I myself have among other things, been involved in measurements of AC earth field measurements down at sub pT levels, low level atmospheric ELF measurements, and extreme low light levels down to single photon counting, and there are plenty of other examples for those willing to look for a broader scope.
Then there is the "young guy syndrome", asserting that "old geezers knowledge" is totally obsolete, and only "the young experts knows", ... absolutely proposterous!
( - actually I once was there myself...'😀' , only to be proven wrong! )
Unfortunately, it seems that High End Audio" is THE field of electronics that unarguably has the absolutely highest content of hype whatsoever. This forum is literally crammed with threads to prove it, too. One of the most strange impressions, is that fact that the level of self certainty seems inversely proportional to level of education - and simultaneously that any level of higher education in electronics is an automatic disqualifyer. Conversely - the higher level of education - the higher level of scepticism to any "scientifically unproven" postulate.
That is , again , not saying that " non electronic" persons are unable to possess knowledge of the trade and topics. Leif Forsell, of Forsell and Air Tangent fame, comes to mind - he is a dentist...
OTOH - there is Herr Ennemoser, and his "Nirvana Laquer".....
Finally - remember : I am not pecking at anyone here specifically. I also know that John Curl , among others, have made some very successful designs in audio. Several other posters in this thread also posesses great knowledge of the field and have contributed immensely to the level of this forum.
Have I contributed any ? Hopefully I have, - in some thread or another. Unfortunately, I have too little time to investigate my own potential ideas, being one of many out there with a daytime job that craves quite alot more than 9 to 5. So - I'm left with the interest in the topic, - and some spare time to read about other peoples ideas.
Alas-while I go find my "Jameson" fire extinguisher and sit back- I bid you all a good weekend! 🙂
EDIT : I just remembered another field, slightly related, that has a similar or even higher level of hype, and which I am currently investigating along with my son - tube guitar amps!
Quite similarly - very few guitarists have any clue in electronics - but some have, and have made remarkable impact in their field.
BTW - Leo Fender couldn's even play guitar, and Jim Marshall was a drummer........
Originally posted by syn08
For the sake of this thread, your 30yrs experience is a handicap not an asset.
scott wurcer said:
This is exactly the kind of attitude and self appointed " ME only Knows", that this and some other threads are full of, and which represents a level of silliness that is quite ridiculous, and also quite destructive in terms of exchange of ideas and knowledge.
First - I am not attacking anyone in persona, rather than the attitude of such opinions.
There is a rather strange phenomenon associated with "High End Audio", where a number of designers, some educated and some self thought, and very few are theoretically highly educated, - that the problems of High End are unique to this feld, and noone else in other fields of electronics has any clue at all to what's going on, - except the very same self appointed gurus, - or maybe an inner circle of the same.
This is, of course, not saying that some of these gurus have made some very successful designs, which some most certainly have.
Quite a lot of the content of this thread deals with grounding and shielding techniques, where in education, Ralph Morrisons " Grounding and Shielding Techniques in Instrumentation Design", first edition in the late 60s, is still the Bible, and being used in several colleges and universities all over. Sofar, I've seen nothing over the years to prove this Bible wrong! But of course, new materials and a other new tricks have been developed since then, and still are. There's just even longer in between them.
The assumption, that signal purity and noise control, is special to High End, is just another piece of rubbish thinking. Quite a number of topics in various fields of instrumentation deals with much smaller signals than High End Audio, and have exactly the same problems to combat, to an even higher degree than High End. I myself have among other things, been involved in measurements of AC earth field measurements down at sub pT levels, low level atmospheric ELF measurements, and extreme low light levels down to single photon counting, and there are plenty of other examples for those willing to look for a broader scope.
Then there is the "young guy syndrome", asserting that "old geezers knowledge" is totally obsolete, and only "the young experts knows", ... absolutely proposterous!
( - actually I once was there myself...'😀' , only to be proven wrong! )
Unfortunately, it seems that High End Audio" is THE field of electronics that unarguably has the absolutely highest content of hype whatsoever. This forum is literally crammed with threads to prove it, too. One of the most strange impressions, is that fact that the level of self certainty seems inversely proportional to level of education - and simultaneously that any level of higher education in electronics is an automatic disqualifyer. Conversely - the higher level of education - the higher level of scepticism to any "scientifically unproven" postulate.
That is , again , not saying that " non electronic" persons are unable to possess knowledge of the trade and topics. Leif Forsell, of Forsell and Air Tangent fame, comes to mind - he is a dentist...
OTOH - there is Herr Ennemoser, and his "Nirvana Laquer".....
Finally - remember : I am not pecking at anyone here specifically. I also know that John Curl , among others, have made some very successful designs in audio. Several other posters in this thread also posesses great knowledge of the field and have contributed immensely to the level of this forum.
Have I contributed any ? Hopefully I have, - in some thread or another. Unfortunately, I have too little time to investigate my own potential ideas, being one of many out there with a daytime job that craves quite alot more than 9 to 5. So - I'm left with the interest in the topic, - and some spare time to read about other peoples ideas.
Alas-while I go find my "Jameson" fire extinguisher and sit back- I bid you all a good weekend! 🙂
EDIT : I just remembered another field, slightly related, that has a similar or even higher level of hype, and which I am currently investigating along with my son - tube guitar amps!
Quite similarly - very few guitarists have any clue in electronics - but some have, and have made remarkable impact in their field.
BTW - Leo Fender couldn's even play guitar, and Jim Marshall was a drummer........
scott wurcer said:
It was just a bit odd, Scott, to see bats slam into screens. They can see barbed wire fences and even smaller gaps in different fences..and tuck their wings in and 'float' through the holes..and do this day in-day out.
We did not plan ultrasonic absorption in the formulations --- but that was the result.
I mention it as a point that is similar, in it's own way to doing seemingly retarded experiments. Like Parallel fusing, something I mention for the guys in the UK who would like to rid themselves of the sonic effects of the mains fuse....to some degree.
As an Aside, there, AuroraB: The guys in the thread are not attempting to play or act on ego when they say such things. But if it smarts, ask yourself why. Speaking for myself, I LIKE to be wrong, as it shows me an area of ignorance, so I can fix it.
I keep attacking the things I do not know..at the same time I reasonably and steadfastly refuse to take 'recorded knowledge' at face value-and thus do my best to learn things that are new, or, in my opinion- to learn the truth, the nature of the 'fact'. This, instead of the rote and simple 'information'-which is meaningless.
Half the time they turn out to be old and already covered, like jokes ("This Centurion walks into a bar...." etc), but they can be new to me, or new to our generation or group, 'in time'.
Like there is a little old rule we learn from Electronics 101. It is a fundamental rule we were first taught. Yet, we, to almost a man, in the entire world of high end audio design...... have conveniently forgotten it. And it has turned around and screwed the whole world of high end audio square in the ***. We all know this rule, but fail to understand HOW important it is, to excellent sonics. The improvement in sonic quality is DRAMATIC..if it is followed religiously. You could almost say, that we learn it again, at the end. What is that rule? Another one of those points I like to keep to myself. 🙂
And as for Dentists.... Rudy Van Gelder was a total MONSTER in his recording skills. But he was also a Dentist. It may burn the *** of the pros, at times..but...sometimes the 'naturals' (Like Rudy) just waltz in..and make it look simple.
Deal with it. 🙂 I trhink you get it, though.
So back to the Blowtorch and such. Parallel fuses anyone? Giv'er a go! It's a dang easy test!
As for commercial viability, the price increase on a 4 rail power amp, plus mains, plus pre section would be like....$10, max. That translates to..uh..$60 at retail, for ultra reliable fusing. The kind that minimally impacts sonics. Circuit breakers are notably more failure and 'danger' prone. The multiple miniature fuses also create less eddy currents due to smaller sizing. Less 'resonant' (reflective, complex LCR changes and 'areas/modes) cavities along the path, is one way of phrasing it. You end up with a better, more linear, and larger current pathway with less problems over multiple draw scenarios.
passed the 1/2 hour edit time limit so..
For example, in North America, we have a single AC rail power fuse, in our single sided AC power situation.
Instead of a SINGLE AC power fuse....at let's say..15A/125VAC in a given 250W/PC power amp....try a FOUR fuse holder..and put in Four 3A Fuses in parallel. I think you'll like it. The change in overall manufacturing expense teeters at a horrible $2-3. Not bad for what will equate to a change in sonics that would be valued at about $500 to $1000 in the 'high end' world. If not valued MORE..as we have yet to hear it, in the common sense of being available to buy, at all. If you look at what a fuse is, it is in one sense, a transient draw limiter.
When you swap out a fuse (in a controlled bench situation, of course) for a copper bar, the change in sonics if frightfully seductive.
This returns/retains a NOTABLE amount of that quality. And maintains a very solid fusing scenario, which is the critical point.
For example, in North America, we have a single AC rail power fuse, in our single sided AC power situation.
Instead of a SINGLE AC power fuse....at let's say..15A/125VAC in a given 250W/PC power amp....try a FOUR fuse holder..and put in Four 3A Fuses in parallel. I think you'll like it. The change in overall manufacturing expense teeters at a horrible $2-3. Not bad for what will equate to a change in sonics that would be valued at about $500 to $1000 in the 'high end' world. If not valued MORE..as we have yet to hear it, in the common sense of being available to buy, at all. If you look at what a fuse is, it is in one sense, a transient draw limiter.
When you swap out a fuse (in a controlled bench situation, of course) for a copper bar, the change in sonics if frightfully seductive.
This returns/retains a NOTABLE amount of that quality. And maintains a very solid fusing scenario, which is the critical point.
how do you ensure the correct current interruption with multiple fuses in parallel? Do you need to do anything to balance the currents?
At the same time 4 nonlinear devices in parallel will still be non-linear, perhaps more so depending on the non-linear nature of the part and where on the curve you are operating. The connections in parallel will be better of course.
There are people trying to commercialize audio fusesFuses and silver plated fuse clips are a normal commercial item More Fuses and Bussmann check out 1A1907-05 for the optimum construction.
At the same time 4 nonlinear devices in parallel will still be non-linear, perhaps more so depending on the non-linear nature of the part and where on the curve you are operating. The connections in parallel will be better of course.
There are people trying to commercialize audio fusesFuses and silver plated fuse clips are a normal commercial item More Fuses and Bussmann check out 1A1907-05 for the optimum construction.
Personally, I think that the single QUALITY fuse or circuit breaker is an easier solution. Still, in principle, the parallel fuse approach would probably be effective, but impractical.
1audio said:
The point of me mentioning the four 3A fuses to replace the single 15A unit, is that part of the rating is thermal, and the proper balance can only be found via playing with the situation.
As the fuses are thermal and current limiting, they tend to balance out against each other in the (near) instantaneous sense. As the pathways are quadrupled on transient draw, with regards to cubic or volumetric considerations (circular mils, etc) the non-linearities are reduced. The sonics seem to indicate that to be the effect that is heard.
The comparison that one's brain usually tries to make is of that of a multiple output power circuit, but that analogy does not work here, as it is the fuses themselves that balance out. And the four fuses share the thermal load, over what is likely a greater surface area. Thus the hunting for the values that are correct, and the conservatism in the initial starting (experimentation) point.
The reality is also that I'm not really scientifically trained, but trained as a tech. So, in essence, I'm more of a hack with a good brain, a capacity for logic, and decent ideas. When it comes to the full explanations, I can only go so far. But I do know how to correlate what I hear.
You'll have to find something like, let's say.. a power amp that has the fusing (fuse holder) bolted to the chassis (not board mounted), so you can sub in a four fuse holder, to do this simple test. You'll likely have to juggle the fusing to get it right. I actually ..uh.. make my own fuses. 🙂 Sort of.
The musing of the possibilities (on it's own) should illustrate to an adept mind the possible enhancements that it could bring to a given amplifier power rail, for example.
KBK, I tend to agree that similar fuses (from the same box for example) will track, partially because the tempco will be such as to balance the fuses. I also think that having more surface area for heat dissipation, as well as contact surface is important, but not to the extent of putting 4 fuses in, when one GOOD fuse would cost about the same.
Don't be too overwhelmed by those here with better 'credentials'. I hired my first PhD back in 1974 for a special project, but they rarely taught me what I already didn't know about audio design, and even can't understand why I worry about it. What is important is an open mind, and a reasonable understanding of how we normally think that things work.
It seems to me that even our traditional explanations of physics, engineering, etc, are just approximations that often fall short.
Don't be too overwhelmed by those here with better 'credentials'. I hired my first PhD back in 1974 for a special project, but they rarely taught me what I already didn't know about audio design, and even can't understand why I worry about it. What is important is an open mind, and a reasonable understanding of how we normally think that things work.
It seems to me that even our traditional explanations of physics, engineering, etc, are just approximations that often fall short.
The power system in most equipment consists of a transformer for voltage range and power line isolation. A rectifier usually feeding a bulk storage capacitor followed by a voltage regulator. All this stuff is there to isolate the application circuit from the power line fluctuations and noise.
Since the power line varies quite a lot, headroom is usually applied somewhere between bulk storage and the voltage regulator. It would seem this effect would also isolate perturbations caused by fuses.
Now many power amplifiers do not regulate the power amplifier output stage, I understand about speaker fuses or power amp fuses, but this thread is nominally about pre-amps. Do all of you who advocate a complex fuse solution mean for pre-amps as well?
What am I missing?
Since the power line varies quite a lot, headroom is usually applied somewhere between bulk storage and the voltage regulator. It would seem this effect would also isolate perturbations caused by fuses.
Now many power amplifiers do not regulate the power amplifier output stage, I understand about speaker fuses or power amp fuses, but this thread is nominally about pre-amps. Do all of you who advocate a complex fuse solution mean for pre-amps as well?
What am I missing?
In hi end hi fi design, we worry about almost everything. However, a power amp would be more prone to fuse problems, except for the fuse holders which are pretty marginal.
In another DIY thread I recall reading a post by someone that if a fancy power cord made a difference, the thread poster would go to work on the power supply design. Compared to the cost of a fancy power cord a great number of power supply improvements can be made.
I do understand about covering small details, after all, each problem that has an available solution, is one other issue that is far less likely to contribute to a design defect in the final design.
Still, the fuse issue comes as a surprise.
I do understand about covering small details, after all, each problem that has an available solution, is one other issue that is far less likely to contribute to a design defect in the final design.
Still, the fuse issue comes as a surprise.
It is typical for highend. Circuit, layout, PCB design issues, that are responsible for 98% of sound differences, are not discussed in deep. Power cords, fuses and wires, that cover the rest 2%, are discussed, supported by huge general public interest. The main reason is that you need no qualification to change power cord or fuse.
hermanv said:
Herman,
Are you talking about fuses *before* the storage caps? They would not necessarily vary in impedance by cyclic heating caused by the music signal, but by the (double) mains frequency. I have difficulty to image an impact on the signal, since the fuse impact would be indistinguisable from the *normal* mains ripple anyway.
If the fuse is *after* the reservoir caps, presumably signal currents from the supply would cause cyclic temperature effects. Again, these would most probably fall in the same effect as effects from non-zero supply impedance , except of course when the supply is regulated. In this last case one can imagine an effect of the fuse on the supply.
Let's try to put some numbers on it. A quick check showed me that a 6A Bussmann has 17 milli-ohms cold (<10% of rated current) resistance. I don't know how that rises with current; lets say it inceases 10-fold for 2A (a wild guess, I know). The delta-voltage drop would then be about 0.34V with 2A peak signal current. Can that be audible?
That 2A signal current in 8ohms gives 16V peak signal. The 0.34V supply variation, with, say, 60dB PSRR will give 0.34mV across the speaker. That's about -93dB below the signal.
I did make a lot of assumptions here. Yet, it does seem that the effect *could* be audible under specific circumstances.
Can anybody firm up the numbers?
Jan Didden
Hi Jan;janneman said:
If I put fuses on the secondary side I would tend to put them between the bulk storage and the regulator. In theory this would be reasonably fast, yet the regulator would remove most of the fuse "ripple". With multiple or "split" supplies I am not very happy with the idea that one voltage could pop a fuse while leaving the other voltages in place. Additionally a fuse blown indicator is a bigger problem with multiple fuse circuits (I don't mean parallel fuses, presumably if one blows they all blow). Don't forget the added complexity of protecting for mains transformer failure or the bulk storage or rectifier failure.
The second part of your response seems to deal with power amplifiers. I think this would be a separate discussion. If there is no output power regulator then the fuses could easily be a big deal.
Please understand that I'm not saying the fuse idea isn't needed, but I do think that several contributors are mixing power amp and low level amplifier circuitry.
So my question remains: Is special fuse treatment or are special fuses needed for low level circuits?
OK, I understand. I agree that if you have a fuse after the bulk storage, and before the regulator, it is very unlikely that it can be detected in some form of blind test.
OTOH, with pre-amp type equipment, I wouldn't bother with any additional fuses to the mains fuse anyway. With power amps it is more critical (for me) as a fault may damage expensive speakers.
In power amps, I would choose for a comprehensive speaker protection with a high-quality relay rather than supply fuses. Faster. The blown-out cone may already have past the sweet spot by the time the fuse blows 😉 . YMMV.
But if one would use supply fuses in an unregulated power amp supply, after the bulk storage, I can image that there is some audible effect at higher frequencies where PSRR deteriorates as speculated in my previous post.
BTW Anybody has any update on my guestimates in my previous post?
Jan Didden
OTOH, with pre-amp type equipment, I wouldn't bother with any additional fuses to the mains fuse anyway. With power amps it is more critical (for me) as a fault may damage expensive speakers.
In power amps, I would choose for a comprehensive speaker protection with a high-quality relay rather than supply fuses. Faster. The blown-out cone may already have past the sweet spot by the time the fuse blows 😉 . YMMV.
But if one would use supply fuses in an unregulated power amp supply, after the bulk storage, I can image that there is some audible effect at higher frequencies where PSRR deteriorates as speculated in my previous post.
BTW Anybody has any update on my guestimates in my previous post?
Jan Didden
Your estimates seem OK to me. If I come at the problem from the other end I reason as follows.janneman said:
An average speaker sensitivity is about 90dbSPL. A 2 amp speaker fuse would blow if average power exceeded 105dbSPL (8 Ohm speaker). That's pretty loud so a two amp fuse seems reasonable.
A 2A AGC (fast acting fuse) has a series resistance of about 0.075 Ohms cold or about .125 Ohms at current carry limit. This results in a drop of about .25VRMS considerably more for music peaks. I'm with you, even though the fuse is a simple answer it doesn't seem to be a good answer. Active protection or a relay seems better, although relays with very low contact resistance are of necessity kind of slow.
So if I was designing a power amplifier, I'd probably plan on a single mains fuse to cover hardware device failure and an active protection circuit to cover both misuse and to protect the speakers from DC. The active circuit would assume the output stage was still operational with possibly a relay back-up to protect speakers from output device failures.
Given the price of todays "Hi end" amplifiers, I think regulating the final stage voltage or at least a capacitor multiplier is economically feasible. Either would provide some more "hooks" for control with a protection circuit.
janneman said:
The whole calculation will hold at very low frequencies. Otherwise, for all practical use and calculations, the fuse will drop a constant voltage that will not impact anything but the output max swing.
http://www.cooperbussmann.com/pdf/d24d694f-c843-4f13-ae83-a096caaf2034.pdf
It shows a 2.5A fuse having a max drop of 213mV, while a 12A slow blow (more realistic to use) has a drop of max. 114mV Of course, the lower the fuse rating the higher the voltage drop.
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