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Old 6th Apr 2019, 4:58 pm   #641
Craig Sawyers
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Default Re: Audiophoolery?

Yes indeed - the velocity factor is in the range 60-80% the speed of light for most common cable constructions, and you can consider audio cables to be in that sort of range. It is not at all relevant to most aspects of audio cables (but not all - it depends on the frequency, which for RF interference needs to be considered)

The peak charging currents can be tens of amps on the rectifiers and transformer secondaries when the associated amp is being worked hard, or on transients longer than a mains cycle. But the turns ratio, for a transistor amplifier in the range of 8:1, so the primary current pulses are much less - but could get to surge peaks of a few amps. Generally the rear chassis fuse on a power amp is usually something like 6.3A slow blow for that reason.

That is why quite a few amplifiers now use power factor corrected switched mode supplies to cut down on the high current surges from conventional supplies, which can give issues in meeting conducted EMC specs necessary as part of the CE marking test programme.

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Old 6th Apr 2019, 5:09 pm   #642
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Fuses should be de-rated a bit too. The rated current is that which will blow them in 1000 hours if maintained as a steady DC value. 1000 hours would be a bit too frequent for peace of mind, but then allowances have to be made for duty factor, surges etc. So a 6.3A slow blow is a good choice for a moderately powerful domestic amplifier. Class A room heaters are monumentally inefficient, but they don't do surges, so if anything, they're a lot easier to pick fuses for.

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Old 6th Apr 2019, 6:23 pm   #643
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Default Re: Audiophoolery?

I'm afraid that in my experience Class A room heaters and other powerful amps too can blow quite big fuses at first switch-on, when the mains transformer energises itself and then starts charging all the power supply capacitors and warming up the near-short-circuit valve heaters. That was how I discovered the enormous range of blow characteristics which hide behind the letter T on a fuse.

Cheers,

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Old 6th Apr 2019, 6:25 pm   #644
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The other thing that needs to be borne in mind is switch on surge. If the mains is switched on at mains zero crossing, you get doubly hit with magnetizing current for the transformer core, and charging current in the capacitors (although the magnetizing surge is much more than capacitor charging). Worse with toroids as compared with open frame because of low leakage inductance.

You can easily get an initial surge when the core has no field determined by the mains voltage and the primary resistance. I've just measured a 300VA toroid and the primary resistance is 4.6 ohms, so the maximum surge can 52A (240/4.6) until the field in the core is established (1/4 of a cycle - so 5ms) - then the primary inductance controls the current. But a 50-odd amp spike can trip the breakers in your house even if it does not blow the equipment fuse.

There are various schemes to manage this surge to do with cheap and cheerful passive using thermistors, or usually more sophisticated relay based delay. So on startup, a power resistor is in series with the transformer primary (10 or 20 ohms, 20-50W - that sort of range) and then after a delay of around half a second delay, relay contacts shorts out the power resistor.

Great fun and games!

Craig

PS This is far too serious stuff for the topic of the thread
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Old 6th Apr 2019, 8:04 pm   #645
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The fourier transform of an instantly switched AC waveform includes a DC transient component, and considering the impedance of a transformer down in the frequency range of the transient, a large current transient flows which can easily saturate transformer cores and that causes problematical currents at the power frequency and its harmonics.

The ideal turn-on is an AC waveform growing slowly from zero and the reverse for turn-off. It's related to the need for a steadily diminishing AC signal and not an abrupt turn-off or removal for demagnetisers.

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Old 6th Apr 2019, 10:36 pm   #646
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Default Re: Audiophoolery?

May I point out an error in post#207. According to the advert in the link posted therein, the 13A mains plugs & socket branded 'Isoclean' do have gold plated pins/sockets
(Not that I subscribe to this kind of audiphoolery or would ever think of paying, even if I could afford to, the prices charged for such items.
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Old 6th Apr 2019, 11:20 pm   #647
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Indeed - I have quite a number of patents in my name (but none in my ownership, alas), so I understand the patenting process quite well.

Craig
You are a genius. In this day and age the last thing you want to do is own a patent yourself. If you ever do, try to transfer the ownership of it ASAP. I will explain why:

Firstly, the patent exposes the owner to 3 risks.

1) somebody else sees the published work, because the patent has put it in the public forum, concludes (rightly or wrongly) that the work uses some of their IP. They start a case and you end up paying large legal fees to your Lawyer to defend your work.

2) You, or somebody else notices that somebody else's work looks like it has borrowed from yours, or even downright stole your idea. You spent money to protect it, so now what should you do ? Your legal team advises you to start a case, as the years go by nothing much happens except you pay a lot of legal fees.

3) You are sitting quietly at home and have not instructed anybody to do anything. Then in some legal office somebody is asked by a company using the patent to review something or do something related to the patent. Because you own it, a week later you get sent a bill for some $1000's of dollars, they call that a "patent maintenance fee".

It is almost inevitable that really good ideas and inventions get copied pretty quickly, especially in China etc. So now a lot of companies have abandoned the idea of patents . They simply are first to the market with the product and keep the workings of their devices as secret as possible (which has been aided by secure firmware). This way they are immune from costs of patents, claims of using any other people's IP, which are usually baseless anti-competitive attacks anyway. And it saves a fortune on lawyers.
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Old 6th Apr 2019, 11:31 pm   #648
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Because I build my own amps, I use Neutrik Powercon mains connectors. These are usually used on pro-audio gear because (a) they are locking and (b) either rated at 20A or 32A so the contact resistance is low and (c) they are cheap (well, reasonably so).

The 32A ones from Farnell are 15.72 for the plug and 9.38 for the socket.

The 20A ones are 5.70 and 3.34. All plus VAT of course.

>1000 mating cycles and <=3 milliohm contact resistance at end of life for both the 20A and 32A versions. Gold plated contacts, of course.

For the power amps (active XO and a total of ten channels of power) I use 8 contact pair and 4 contact pair Neutrik speakons thougout, which means I cannot wire a woofer output up a tweeter and toast it. Provided I wire the internals of the speaker right, and the speakon/speakon cable right. Check each three times, and connect it up. End of story,

These again are locking, take 30A rms and 40A on a 50% duty cycle, 5000 mate cycles, and gold plated. Same sort of price as the 32A powercon.

All massively overrated for domestic audio, but they really are just fit and forget.

Craig
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Old 6th Apr 2019, 11:43 pm   #649
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It is almost inevitable that really good ideas and inventions get copied pretty quickly, especially in China etc. So now a lot of companies have abandoned the idea of patents . They simply are first to the market with the product and keep the workings of their devices as secret as possible (which has been aided by secure firmware). This way they are immune from costs of patents, claims of using any other people's IP, which are usually baseless anti-competitive attacks anyway. And it saves a fortune on lawyers.
The one thing that I currently license is the subject of a written agreement, and is not patented for the reason you give. It is simply an industrial secrecy undertaking.

And remember that James Dyson took Hoover to court for plagiarizing his personal cyclone patent in the early days. He mortaged the house to pay the legal fees. And he won.

That bankrolled his now 8Bn fortune. Mansions in three countries, and a 100 metre long superyacht.

And you are right, the Chinese are arch plagiarizers. There was a perfect case a couple of years ago. Guy invented a new type of folding selfie stick. Patented it, and then disclosed it on the web as part of a crowd funding campaign. Two weeks later, not only had the Chinese copied it from the patent drawings, but had tooled up for volume and were selling them.

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Old 7th Apr 2019, 12:41 am   #650
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Although I started my professional career as a design engineer, a series of circumstances led to me becoming first a patent examiner with the UK Patent Office and then a Patent Attorney (now long retired).

US patent law has always been different from the rest of the world. At one time, actual "reduction to practice" was indeed a requirement, but that was amended long ago so that "constructive reduction to practice" by means of an "enabling description" that (in theory) would allow the skilled person to construct a working embodiment from the paper description, is sufficient.

I fear that the standard of scrutiny of the description of embodiments on both sides of the pond has diminished somewhat since when I joined the patent profession in 1976. Basically, whereas the emphasis in the UK used to be on ensuring that the inventor had provided a teaching of how to carry out the invention (so that the public could freely use the invention once the patent had expired), the emphasis of examination is now directed to the claims that protect the invention (so that the public know what they cannot do while it is in force). Under the old UK 1949 Patents Act that I trained under, the examiner had to read the description from start to finish, checking that it made technical sense, comment of any obscurities and suggest amendments that would make things clearer, and then write a comprehensive abridgment of all its technical content for the benefit of the public. Amendment of the description of US patents has long been prohibited, one exception being the correction of errors of translation.

The present 1977 Patents Act, which was drafted to be consistent with the contemporaneous European Patent Act, changed things somewhat. Examiners no longer had to write abridgments as a (short and therefore often of little use) abstract had to provided by the applicant, and so the bean counters decided that the previous thorough scrutiny of the description was no longer necessary. When performance-related pay was introduced there was a positive incentive to comply: the longer you spent on a case, the fewer cases you would get through, the worse your performance and your prospects of promotion and/or performance bonuses.

Now when I joined the Patent Office in 1976, most of the examiners in my group were chartered engineers who had spent time in industry or Post Office Engineering before joining the Patent Office, and really knew their circuitry. At least one used to set HNC/HND-level electrical/electronic examination papers for technicians. In response to political pressures to cut costs and meet civil service manpower targets (regardless of the amount of work needing to be done), in the 1980's most of the experienced people who happened to be in the right age band took voluntary early retirement when it was offered on really advantageous terms that were too good not to take up ( to be replaced by cheaper inexperienced graduates a few years later), so that by the time I left in 1989 I was one of the last to have had any real experience in circuitry. As the higher management echelons became progressively occupied by people from outside who had no actual experience of examining but plenty with managementspeak, the thrust has been to progressively reduce the amount of intellectual effort required by examiners to increase "efficiency" and allow costs to be reduced even further. There was even a proposal a few years ago to change the law so that amendment of the description of a patent application should be disallowed so that examiners would not need to read it in any detail. This was never adopted (the law change at least. I don't know what current practice is!).

A similar sequence of changes apparently occurred in the US. In the 1990's I had a case where the US examiner had clearly not understood the invention. In the end I dealt with three different examiners, and got it granted as filed after 5 or 6 official actions. On discussing things with my counterpart in the US (also an ex-engineer), he observed that the US Patent Office had a high turn-over of examiners, who often used a stint of examining as a stepping-stone in qualifying as a patent attorney. Thus having applications examined by inexperienced people who did not understand the technology was unfortunately commonplace. I don't suppose things have improved any.

Apologies for rambling on, but I thought it might be useful to explain why it is that patents can get granted for things that, to the expert eyes of forum members, don't work. They might have been examined by people who have done their best, but were possibly out of their depth and probably incentivized to maximize throughput.

edit,

Just read the posts above, which appeared while I was composing. I don't want to stray overmuch from the topic of this thread, so will only observe that the little guy is always going to be disadvantaged by the cost of protection. Unless you file a patent application in China, you will have no protection there, and the Chinese will be free to manufacture and sell the goods in any country where you have not applied for protection yourself. Few people appreciate that Lego was actually invented by a British inventor who only applied for protection in the UK. Lego realised this and were therefore able to manufacture and sell their version legally throughout Europe and the rest of the world. I never had experience of patetn enfrocement in China, but was assured by those who had that it was no different in principle from attempting to enforce a US patent in Texas (where patent trials are by juries who normally decide in favour of a US-based party over a foreign party).

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Old 7th Apr 2019, 1:58 am   #651
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Sorry, it was my error in reading that plug advert, I focused on the Rhodium plated plug and didn't spot the gold plated one (and socket). I see there are also ceramic fuses for plugs, so the glass ones must be for the equipment end of things. So their stuff looks legal. Still pointless, though.

Interesting that the main mouldings of the plugs are translucent. Are these things based on the inspectable-without-opening ones for medical applications?

Ah, 5 drive amps per speaker goes with the Linkwitz speakers...

The one of my US patents whose number I can actually remember is 6509800, and yes, I did build one and it did work. It's been interesting watching the citations list growing. The firm wanted patents and gave a 1000 tax-paid bonus. They had a mutual access agreement with Tektronix etc. so we competed by getting products out first, not by trying to sue each other's socks off.

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Old 7th Apr 2019, 6:33 am   #652
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That was a really interesting post Emeritus. The last few of my patents were with the assistance of old guard patent attorneys on both sides of the pond, who knew their way around the examination system. But you are certainly right that only one of those had actually been "reduced to practice". That was actually discontinued before publication, and I went for a written licence agreement for exclusive use of the invention, which has run sweetly for the last decade.

And David - perfectly right - Linkwitz (RIP) LX521, currently undergoing a massively expensive upgrade to LX521.4. So 8 amps to 10, new analogue crossover with outboard over-the-top power supply and Jung superregulators (power supply integrity is a particular foible of mine) - and by the time casework is taken into account that is somewhat north of a grand.

The real pain is heatsinks. Because they are extruded, they are always banana shaped, with a back that is very far from flat. So un-flat that you cannot just bolt up semiconductors and expect any sensible heat transfer even with grease. In fact Fischer say in their product literature that if you require a flat back (and who wouldn't?) that they recommend the user machine the back flat! For me that involve a laborious hour with abrasive strip for each sink.

Craig
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Old 7th Apr 2019, 8:52 am   #653
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I used to have access to a Bridgeport at work which made life easier, but it still needed the lowest feed speed to get the best surface finish. I think Alcan-Booth offered a 'rectifying' process to give straighter extrusions. A lot of HP instruments in the 70s and 80s had a screened set of boards plugging down onto a mother-board. The screening was assembled from slot-together extrusion, and even the apertures for the self-threading screws were extruded in. It had to be fairly straight.

Siegfried was one of the managers in marketing in Sonoma county when I worked for that group. A very decent chap. It was normal for marketing people to have had plenty of design experience. Marketing was quite distinct from sales.

David
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Old 7th Apr 2019, 10:43 am   #654
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Marketing was quite distinct from sales.

David
And so it should be, very different disciplines. A lot of engineers with purely engineering backgrounds don't 'get' that, and neither do they get that both subjects are complex and specialised, just as their own design engineer or whatever branch of engineering is. They often 'see' a simplistic view of what products to make and how they should be sold, and dangerously, based on personal, non-qualified opinions. There some very clever, very successful businessmen who wouldn't have a clue how to design a piece of hifi equipment, but they understand the worldwide marketplace and what products would sell and where, and others know exactly how to get people to buy them. The best designed piece of kit in the world will fail if not marketed properly - and that includes pre design market analysis, and if not sold and distributed properly.
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Old 7th Apr 2019, 11:03 am   #655
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How many of us have worked on equipment designed clearly, by boffins and not engineers? Usually serviceable items are a real nuisance to get at in such designs.

As for gear controlled by the accounts department ...

Have just done an Internet search for 'audio grade volume knob', no joke, at one time you could buy a wooden knob for your amplifier which would yield all manner of improvements. They use to sell for $499-odd, looks as though the original company are no longer trading.

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Old 7th Apr 2019, 11:14 am   #656
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My electrostatic headphone amp was designed by a guy in the US called Kevin Gilmore. After I'd finished the beast, I sent a piece of lignum vitae to him, enough for a knob for him and one for me.

So for no other reason than decoration, I do have a rare wood knob on my headphone amp. Makes no difference to the sound quality one single jot of course, but it looks and feels great!

Craig
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Old 7th Apr 2019, 11:19 am   #657
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My electrostatic headphone amp was designed by a guy in the US called Kevin Gilmore. After I'd finished the beast, I sent a piece of lignum vitae to him, enough for a knob for him and one for me.

So for no other reason than decoration, I do have a rare wood knob on my headphone amp. Makes no difference to the sound quality one single jot of course, but it looks and feels great!

Craig
Try Pinus Radiata

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Old 7th Apr 2019, 11:31 am   #658
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Siegfried was one of the managers in marketing in Sonoma county when I worked for that group. A very decent chap. It was normal for marketing people to have had plenty of design experience. Marketing was quite distinct from sales.
David
Good to hear that you knew SL. I got the impression that he was a really nice chap. If anyone was out at Corte Madera where he lived and got in touch he'd spend a day showing them the various speakers and listening to them.

He spent a decade or more fighting prostate cancer, and eventually died age 82 late last year. He was still doing interviews from a hospital bed in his front room shortly before he died! Search you tube for that and other lectures by SL at the AES etc.

The good news is his widow still holds open house, with Nelson Pass (who lives locally) often there. The website, SL's treatise on loudspeakers, crossovers, amplifiers and so forth ( http://www.linkwitzlab.com/ ) is safe and being maintained by Frank Brenner. Frank runs MagicLX521 from Germany ( https://www.magiclx521.com/ ), but is also an airline pilot, including Airbus A380's. So he's often at the get togethers in Corte Madera if his flight schedule works out.

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Old 7th Apr 2019, 11:42 am   #659
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Audiophiles suffer from a form of OCD perfectionism, as many do to some extent, and the audio market is simply exploiting their obsession. Like gamblers, audiophiles will not all be wealthy. It is down to human behaviour and there is very little logic in that!
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Old 7th Apr 2019, 12:11 pm   #660
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That's the only real problem I see in audiophilia. I have no issue with the immensely rich swanning around in uber-impractical Ferraris and incendiary Lomborghinis. It's their money and their inconvenience.

What worries me is someone of average means getting bitten by the bug and sucked in by the seductive prose and imaginary advantages. Having to scrimp and save to afford a highly touted mains cable is going to affect the rest of their families. This is where a hobby turns bad. One set of interconnects would buy how many kids a bike for Christmas? It's only an innocent pastime if it affects no-one else.

I suppose it's not as damaging as alcoholism or as nasty as fearsomely expensive folk remedies when the money could have been spent on something which at least had a chance of effecting a cure.

David
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