What causes Inductance... flux density or no flux density?
At Lawrence Livermore National Laboratory, they are an applied science lab. I was told when I worked there they never hired theorists. If they have something not go as planned, they call a university for a therorists to give them ideas. LLNL has to make things that actually work. All people hired are world experts in the field they were hired/needed. They had practical experience. No PHD without experience were ever hired. Experience matters.
Now tell me again how skin effect is actually caused to happen? Or why the HF are at the surface?
THx-RNMarsh
I would argue audio band IS DC. I wouldn't go as far as some of the microwave people I worked with who would scoff that anything under 1GHz was DC, but certainly the higher in frequency you go the weirder things get.
If I read you right you are saying that oxidation of the centre bundle will create a type of very poor litz wire? I must admit I had been thinking of a solid core when thinking of an easy experiment to show if surface oxidation can have a measurable effect. But interesting. I can't at the moment think of a way to corrode the inner without modifying the geometry or dialectric in a way that would skew the results.
Aside: I do have a fondness for semi-rigid on SMA connectors. It just takes impractical to new levels in a hifi, but handy internal hookup between boxes.
Yes that was the reason. And the main reason of a university SHOULD be to teach students how to learn and understand new things. For that I am grateful. I just didn't discover until there that, as an arrogant 18 year old thinking they were the greatest (as we all tend to be at that age) that I actually need some hook of application to help it sink in. So learning some mathematical technique in the first year that you don't use in anger until the 3rd didn't gel with me. Some of it took 20 years before I realised it was useful. But I still am glad I had the opportunity.
Should also note it was an 'all engineering' course, not just EE.
What I found amusing at Harman companies was the mantra of No Invention on the Critical Path, which doctrine led to edicts to reuse designs as much as possible. Of course this is not very interesting to a creative engineer, so I routinely violated it in the somewhat looser environment of the Multimedia groups.
Now one would suppose that what went wrong with some of those products was based on risky innovations. But it really never was---rather, flux contamination in one case, and a mechanical engineer doing an uncontrolled change in a heatsink thickness, to placate the contract manufacturer who was getting some small cracks when bending the material. Then the bracket holding down the power IC was too tight and caused the thinner material to bow and almost eliminate the thermal contact, leading to premature failure of the power IC.
There was also the early baptism by fire, when I walked too close to the edge with an electrolytic's operating voltage. At one point the Rubycon parts were delayed, and a dirt-floor vendor's nominally-comparable part substituted. Some of them blew their cans right off. The caps were of a quality appropriate for a child's toy, that get destroyed a few days after receipt. I had nearly learned my lesson that one should never meet cost targets at the expense of a defensible design. And I was always asked to estimate costs before the design was done, something else to be resisted. If it cannot be, don't suppose that you will be fired for missing the cost target.
JN already commented he is active at a major research facility making things work, he IS a recognized expert. You tossed off a comment that frequencies above 8kHz are forced into oxidation (if present) in a conductor, he said no, he is right.
Huber Suhner HUBER+SUHNER Radio frequency - Seite 279 The BNC's are brass but the N is Stainless and can be expensive. This is on the cables that come with the Keysight Network analyzer and the cal kit. Its almost as expensive as audiophile cables.
he may be correct and may not be in his model of how things work. Sorry JN.
THx-RNMarsh
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I investigated a product with early electro cap failures. To cut costs or increase profit, the electrolytic was not formed at the factory. The product upon power up would do the cap forming. Unfortunately, that step, is normally current limited during charge up to max rated voltage. The product on power up might just look like a short without the current limit... too much current blew the caps. There are all sorts of creative ways to cut costs.
THx-RNMarsh
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In a conversation with O2 (cellular network) the other week about an RF cell issue, they in the end said, we don't have anyone who understands RF here anymore. We just drop a box (cell) into place and turn it on. We only have people who know how to use the GUI to configure them, and IT guys...
Oh, and we've dealt with their so called IT guys, that's another long story.
They're going to be a lot of fun.....I borrowed a pair of JBL L220's and HK Citation amp for a party once...went down very well.JBL M2 spec---- Recommended amplifier power: 1200W/channel into 8 Ohms.
[got them in the house now]
Your M2's could also double as PA speakers for a duo/band etc at your next party.
Dan.
Could someone please explain to John how this paper has nothing to do with audio - or explain to me how it has?john curl said:
Hee hee!jneutron said:
Flux. As flux is low at the centre (as I and jn explained) then your explanation of skin effect is wrong. You are doing things back to front: trying to determine flux from an imagined high inductance caused by an imagined explanation of skin effect. Try reading a good EM textbook.RNMarsh said:
Yes, experience matters - but so does correct theory. Experience unaided by correct theory merely makes people arrogant in their ignorance. We see this on this very forum: people who have been making/selling/writing for 30-40-50 years (so have lots of experience) yet seem blissfully ignorant of some of the basics of the physics and maths underlying their own subject, and so make newbie-level mistakes from time to time. Unfortunately, unlike real newbies, their experience renders them unteachable.
Back in the early eighties there was an affordable and very 'impressive' Novatech All In One that came with large/party 12" 3 ways and sold quite well (especially well to the bogans of the time).
A whole bunch came in for warranty repair because of 'not recording to cassette' fault.
The cause was that four placements of 5mm electro coupling caps did not have rubber sealing bungs fitted !.
Hu only knows how that one got through production and into the stores.
Dan.
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25 years ago, when I worked in the power industry, we had 'network managers' (controlling LANs and associated file servers) whose previous experience was in installing telephone cables. I guess the management thought "well, it's all wires, isn't it?". As I said at the time "They wouldn't recognise an Ethernet packet if one dropped on their foot!".gpauk said:
In order to get improved performance from the file servers they configured them to keep as much as possible in RAM, and only commit to disc when they started a backup (twice a day). As the servers crashed regularly, this mean that files which desktop users had thought were 'saved' to disc had in fact only been transferred to RAM on the server. Hence nothing was safe, so people started saving files to their local disc or floppies instead. I questioned the 'network managers' about this - but they could not see what I was getting at; file server 'performance' was more important to them than actually carrying out the only function of a file server - to save files!
1200W = 30.8dB ref 1W
92dB/W/m + 30.8 ~ 123dB
Elementary, dear Watt-son
You have an adress in Thailand I can have the flowers and condolences delivered to ?
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I believe we have discussed skin effect many times on the Magic Roudabout this thread has become.....
http://www.diyaudio.com/forums/loun...ch-preamplifier-part-ii-3248.html#post3320021
http://www.diyaudio.com/forums/loun...ch-preamplifier-part-ii-3248.html#post3320021
No just a reminder of a particular paper that is mentioned in more recent formal discussion.
That said, I have not thoroughly read the referred paper yet.
So, what is the takeaway from this particular paper, and what is the other stuff mentioned in IEEE Spectrum 7.16.
Dan.
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