Here's a pretty cool picture: File
ole 2 Thyristor Valve.jpg - Wikipedia, the free encyclopedia
but I remember one from _National Geographic_ from about 15 or 20 years ago that was stunning.
Thanks for making me look!
Chris
ps: in the English language Wikipedia, it's under "HVDC".
ole 2 Thyristor Valve.jpg - Wikipedia, the free encyclopediabut I remember one from _National Geographic_ from about 15 or 20 years ago that was stunning.
Thanks for making me look!
Chris
ps: in the English language Wikipedia, it's under "HVDC".
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Love that movie ... so impressive with the special effects they managed to conjure up back then ...
Frank
Yes, a class act indeed. I love that scene as they are walking on the ramp into the generator area.
And in the "control" room:
Captain: What was the power source?
DR. MORBIUS: May I draw your attention to these gages all around here, gentlemen. Their calibrations seem to indicate that they are set in decimal series, each division recording exactly 10 times as many Amperes as the one preceding it. Ten times ten times ten times ten …. on and on and on, row after row, gauge after gauge. But, there is no direct wiring that I can discover. However, when I activate this machine it registers infinitesimally, you see down there in the lower left-hand corner. And, then, when I activate the educator here, it registers a little bit more.
Dr. ???: But this much is negligible, the total potential here must be nothing less than astronomical.
DR. MORBIUS: Nothing less, the number ten raised almost literally to the power of infinity.
Multiple ground points outside the home -
Grounding in the home -- between video/cable/internet and audio systems:
Attached is a quick sketch of the problem when there are just two ground points - one at power entrance panel and one at catv entrance (not at same location). When the two systems are connected together via coax cable, ground potential differences will go thru the A-V equipment instead of grounds (lowest R path). This creates noise and also a path for lightning strikes/transients thru equipment. A ground isolation is needed on the cable - such as a video isolation transfomer or cap coupled rf HP filter to break the ground path. However high volt age transients will go thru. So a surge protection device across the cable is also needed (often a gas discharge tube or other suitable device). Thx-RNMarsh
View attachment Ground Current bypass.pdf
View attachment Ground-Loops.pdf
Grounding in the home -- between video/cable/internet and audio systems:
Attached is a quick sketch of the problem when there are just two ground points - one at power entrance panel and one at catv entrance (not at same location). When the two systems are connected together via coax cable, ground potential differences will go thru the A-V equipment instead of grounds (lowest R path). This creates noise and also a path for lightning strikes/transients thru equipment. A ground isolation is needed on the cable - such as a video isolation transfomer or cap coupled rf HP filter to break the ground path. However high volt age transients will go thru. So a surge protection device across the cable is also needed (often a gas discharge tube or other suitable device). Thx-RNMarsh
View attachment Ground Current bypass.pdf
View attachment Ground-Loops.pdf
Yes, UK transmission and distribution is all AC. Interconnectors to other grids are DC for two reasons:wrinkle said:
- no need to synchronise frequency
- no AC losses in underground/undersea cables
I suspect (not sure) that AC ground losses may exceed AC radiation losses for overhead lines. The main loss is just ohmic heating in the conductors.
If a long transmission line was forced underground (e.g. due to visual impact in a National Park) then there might be some advantage in using DC. It is a matter of balancing the AC losses in the ground vs. conversion losses in AC/DC converters at each end.
Aluminum has less conductance than Coper. The only metal to be better is Silver, just a little expensive. Since, with the increased price of Coper, we'll need soon an armed guard near each cable.
[edit] BTW During last war in occupied France, because the lack of Coper, aluminum was used in some homes for domestic wires, i remember those very fragile wires, with bad contact (alumina) when i was a child.
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I was young when I saw it so all I got out of it was the cool 5-pointed, curved-blade, throwing star! Lots of dents in the walls from watching ...
What? Oh, I thought you said Krull!
http://en.wikipedia.org/wiki/Krull_(film)
... never mind ...
Cheers,
Jeff
DR. MORBIUS: Nothing less, the number ten raised almost literally to the power of infinity.
Yes, a planet with a self destruct button.
Here in the US also. I have encountered it on house wiring jobs.
Not for some time however.
Here's a pretty cool picture: File
but I remember one from _National Geographic_ from about 15 or 20 years ago that was stunning.
Thanks for making me look!
Chris
ps: in the English language Wikipedia, it's under "HVDC".
Neato.
Weren't there also some giant-sized selenium rectifiers at one time?
I would like to turn the conversation back to audio quality, with discussions of 'useful bandwidth' in audio reproduction. Back in the 1940's and '50's, 30Hz to 15KHz was cited as extended high fidelity. It was so, because amplifiers were limited in power, and could not adequately produce lower frequencies, and reproduction sources were not very extended, due to limitations in tape, or vinyl.
With the '60's, partially because it became practical, 20Hz to 20KHz was promoted as 'high fidelity'. This was possible as vinyl reproduction, especially because moving coil cartridges were introduced, better and more extended disc cutters were made, and magnetic tape improved, so even for home use, 20-20KHz nominal response was practical with least with the electronics of hi fi recording and reproduction equipment.
What DOES NOT often get spoken about is what happens WHEN you reduce audio bandwidth with any rolloff, whether deliberate or inherent.
In 1971, in a book called 'Audio Quality' by G. Slot, bandwidth was mentioned, but the MOST IMPORTANT factor, once you got to perhaps 16KHz, was the RATE OF CHANGE of the falloff, not so much the frequency. So, 6dB/octave, was very subtle, while anything beyond 9dB/octave was problematic. Oh, oh! What have we found?
Well, IF we have a natural or added 6 dB slope rolling off the high frequencies, then perhaps a MINIMUM response of -3dB at 30KHz might be OK for most people, but some sharp ears would find it slightly dark sounding, mostly due to the fact that this also implies a 1dB drop at 15KHz, something that even the most conservative tests, (such as double blind) would show as audible.
However, what happens when we extend the bandwidth to 20KHz, BUT make the rolloff greater than 9dB/octave? Slot's work implies that it will sound BRIGHTER, rather than duller, due to some aspect of how we hear.
Now, much of Slot's research and opinion has been actively ignored, with the introduction of the CD. Since 1980, tests have been made, usually double blind, that appear to say that the steep low pass filters that are necessary to make CD's work are NOT a problem. Could this be the case? Maybe most people can ignore these filters, and others are more sensitive.
Now, after a couple of decades of CD dominance, with much back-patting and 'proofs' by distinguished professors, more extended formats are being brought forth, as it is now more practical and possible to do so. Now, the hi end limit seems to be a 50KHz response or a pretty good 10KHz or less waveform with about a 10uS rise-time. What do you know, who would have thought? '-)
With the '60's, partially because it became practical, 20Hz to 20KHz was promoted as 'high fidelity'. This was possible as vinyl reproduction, especially because moving coil cartridges were introduced, better and more extended disc cutters were made, and magnetic tape improved, so even for home use, 20-20KHz nominal response was practical with least with the electronics of hi fi recording and reproduction equipment.
What DOES NOT often get spoken about is what happens WHEN you reduce audio bandwidth with any rolloff, whether deliberate or inherent.
In 1971, in a book called 'Audio Quality' by G. Slot, bandwidth was mentioned, but the MOST IMPORTANT factor, once you got to perhaps 16KHz, was the RATE OF CHANGE of the falloff, not so much the frequency. So, 6dB/octave, was very subtle, while anything beyond 9dB/octave was problematic. Oh, oh! What have we found?
Well, IF we have a natural or added 6 dB slope rolling off the high frequencies, then perhaps a MINIMUM response of -3dB at 30KHz might be OK for most people, but some sharp ears would find it slightly dark sounding, mostly due to the fact that this also implies a 1dB drop at 15KHz, something that even the most conservative tests, (such as double blind) would show as audible.
However, what happens when we extend the bandwidth to 20KHz, BUT make the rolloff greater than 9dB/octave? Slot's work implies that it will sound BRIGHTER, rather than duller, due to some aspect of how we hear.
Now, much of Slot's research and opinion has been actively ignored, with the introduction of the CD. Since 1980, tests have been made, usually double blind, that appear to say that the steep low pass filters that are necessary to make CD's work are NOT a problem. Could this be the case? Maybe most people can ignore these filters, and others are more sensitive.
Now, after a couple of decades of CD dominance, with much back-patting and 'proofs' by distinguished professors, more extended formats are being brought forth, as it is now more practical and possible to do so. Now, the hi end limit seems to be a 50KHz response or a pretty good 10KHz or less waveform with about a 10uS rise-time. What do you know, who would have thought? '-)
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Well, interesting questions, John. When the CD appeared, with brick wall filters, we discovered something new, as you mention: bandwidth flat up to 20kHz and something 'aggressive' with those added trebles.
But, i hope you will agree, it is not in the signal content, as oversampled DAC reproduce the same signal in a nice way. Just to make your mind, if you do not agree, try to digitally down sample a SA-CD to 44.1/16 then up-sample again. You will hear no difference (I presume), since all signals over 2Kz has been removed.
I believe the reason is, as you mentioned, that the problem of the limited bandwidth outside of the range lies mainly in the way it affect the signals 'inside' the audible bandwidth. I conclude it is a matter of group-delay and slew-rate, and may-be the good (natural) correlation between them.
Again, the real problem, from my point of view, is that audible levels of high frequency distortion are part of virtually every hifi system. It's only when you finally eliminate that as a significant component of playback do you appreciate what's actually happening, and you able to tag any sound you hear immediately as being free of it or not. How do you know? Well, if it sounds like a hifi then it's got it, the problem; if it sounds like the real thing then it hasn't ...
CD doesn't hang back from injecting its own deadly dose of this stuff, hence it's acquired a rather unfortunate reputation ...
Just doing some experiments in up and downsampling between PCM and DSD formats, and there's some interesting things going on. There's no doubt that DSD (in at least one case) "distorts" the waveform, in some ways much worse than MP3, so no wonder they sound "different". It makes sense that DSD sounds better to some, because perhaps it adds "nice" distortion, just like valves often do ...
Frank
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