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#81
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"Bob Cain" It doesn't have one. A band limited circuit has a step response slope that is proportional to amplitude - hence it is theoretically unlimited. A slew rate limited circuit, on the other hand, is limited. Right, so the slew rate requirement for transient inputs can't be estimated by the max slope of steady state, HF sinusoids. ** A complete non sequitur. Bob Cain's speciality. ............. Phil |
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#82
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"Bob Cain" What would you calculate for a D/A system with a very high order reconstruction rolloff at 44.1 kHz? Let's say a brick wall for grins. ** Who cares - the parameter is just so easy to measure in any real case. The max possible slew rate for a CD player output is: 2.pi.21,000.2.8 = 0.37 V/uS Wouldn't even bother a 741. .............. Phil |
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#83
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On Tue, 30 Aug 2005 12:19:12 -0700, Bob Cain
wrote: What is the steepest slope of the response of a baseband limited transfer function to a step function input? Can't remember for sure. It doesn't have one. A band limited circuit has a step response slope that is proportional to amplitude - hence it is theoretically unlimited. A slew rate limited circuit, on the other hand, is limited. Right, so the slew rate requirement for transient inputs can't be estimated by the max slope of steady state, HF sinusoids. Isn't it is higher than the latter would indicate? The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Once this was worked out (Cordell?) appropriately low values of good old THD at, say, 20KHz became the test for slewing distortions. Good fortune, Chris Hornbeck |
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#84
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On Tue, 30 Aug 2005 12:35:34 -0700, Bob Cain
wrote: On second thought and from some quick sketches, I think that the zero crossing slope of a signal at Nyquist (Arny's answer) is greater than any transient slope could be. No time for a real analysis. Anyone? Right-i-o. Chris Hornbeck |
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#85
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On Tue, 30 Aug 2005 13:27:32 GMT, SSJVCmag
wrote: Did you see WHAT DREAMS MAY COME in a THEATER? Jaw dropping stuff in there.. Like 2001, it doesn;t/can;t work on video. Sadly, I missed it; was Robin Williams-phobic at the time. But he's truely great, and I shouldn't have been biased. And again, there's David Lynch... Loved Eraserhead and Dune (probably the only person who did) but couldn't follow much beyond that. Takes all kinds to fill the freeways. You sound like you might enjoy early Nicholas Roeg or *any* Hal Hartley. I luvs me some Hal Hartley. Maybe start with _No Such Thing_ to taste-test. Thanks, as always, Chris Hornbeck |
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#86
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#87
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On Wed, 31 Aug 2005 04:29:10 GMT, SSJVCmag
wrote: The odd things he did throughout TWIN PEAKS deserve a lot of attention... Isn't it fun to be on a thread that everybody else has already long ago killfiled? Let's chat. The Twin Peaks thang happened when I was absorbed with working in a local theater group of folks mostly about a decade younger than me. Took up all of my energy, and was well worth it. Norman, from the group, was a Twin fan, so I tried to appreciate it, but couldn't at the time. He was also a _Das Kabinett des Doktor Caligari_ fan, and cast me as the sleepwalker, and a Kerouac fan, and wrote original riffs on his stuff. If you've seen _Slingblade_ you'll have seen many folks from our company. Maybe, like so many things, I'd appreciate it better now. Suppose I should do a re-examination. What Roeg did to MAN WHO FELL TO EARTH should land him in Movie Director Jail.. Or whatever it'd take to keep him from behind a camera with actors in front. Ouch! Mon, you really, really don't want to be taking movie advice from me. arf! Hal Hartley is Personna Incognito... He's a new york school writer-director kinda guy. His company introduced actors like Martin Donovan and Parker Posey, but their most important asset IMO is Michael Spiller the DP. He's also seen in _The House of Yes_, for example. If you like _No Such Thing_, you might check _The Book of Life_, with Martin Donovan as Jesus, PJ Harvey as Magdalena, and Yo La Tengo as a Salvation Army Band. I hate the cinematography (NOT! Michael Spiller's), but otherwise... Different strokes, eh? Chris Hornbeck |
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#88
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Chris Hornbeck wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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#89
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"Bob Cain" Chris Hornbeck wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. ** D/A converters operating close to the half the sampling frequency at max level outputs a full level square wave which the reconstruction filter then turns into a near perfect sine wave. ........... Phil |
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#90
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On Tue, 30 Aug 2005 22:20:58 -0700, Bob Cain
wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. That natural inclination just raises a (very late night) question: wouldn't a step so close to Nyquist F inherently generate (or, in your world, be somehow be equivalent to) a ringing (sinewave) with its fundamental just below Nyquist F? Or is the energy distribution broader and lower? Too late at night; can't think that good even in daylight. Much thanks, as always, Chris Hornbeck |
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#91
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Chris Hornbeck wrote:
On Tue, 30 Aug 2005 22:20:58 -0700, Bob Cain wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. That natural inclination just raises a (very late night) question: wouldn't a step so close to Nyquist F inherently generate (or, in your world, be somehow be equivalent to) a ringing (sinewave) with its fundamental just below Nyquist F? That's my take on the subject. Most posters who have something to say of relevance on this thread also seem to agree. I believe it's accurate. Graahm |
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#92
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On Wed, 31 Aug 2005 15:56:30 +1000, "Phil Allison"
wrote: ** D/A converters operating close to the half the sampling frequency at max level outputs a full level square wave which the reconstruction filter then turns into a near perfect sine wave. An excellent analogy. No, wait, what's the word? Sorta like "syllogy". ? Useful discussions of A/D/A conversions always revolve around the difficult external bits: bandwidth limiting, dynamic range limiting (yeah, nobody but me accept the term and they insist on "dither") and big out-of-band switching transients from the sample-and-holds. Good fortune, Chris Hornbeck |
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#93
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Phil Allison wrote: "Bob Cain" Chris Hornbeck wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. ** D/A converters operating close to the half the sampling frequency at max level outputs a full level square wave which the reconstruction filter then turns into a near perfect sine wave. Right. At first blush I thought that the extra harmonics in a step would add to create a larger rate of change between the two samples. That was wrong. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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#94
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Chris Hornbeck wrote: On Tue, 30 Aug 2005 22:20:58 -0700, Bob Cain wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. That natural inclination just raises a (very late night) question: wouldn't a step so close to Nyquist F inherently generate (or, in your world, be somehow be equivalent to) a ringing (sinewave) with its fundamental just below Nyquist F? I think you mean a square wave and after you band limit it, as Phil pointed out, yes. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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#95
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#96
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"Phil Allison" wrote in message
"Bob Cain" Chris Hornbeck wrote: The highest slope for a brickwall bandlimited signal occurs near zero crossing for a full scale sinewave at just below F. Yep. I erroneously thought at first that a bandlimited step would be higher. ** D/A converters operating close to the half the sampling frequency at max level outputs a full level square wave which the reconstruction filter then turns into a near perfect sine wave. Under those conditions of test and sample frequenceies, you can't sample anything that would result in digital data that would be substantially different from what you would obtain by sampling a sine wave. The difference between the sine wave and square wave would be erased by the anti-aliasing filter in the ADC, not the reconstruction filter in the DAC. |
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#97
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"Don Pearce" wrote in message .. . On Wed, 31 Aug 2005 01:13:01 +1000, Phil Allison wrote: "Don Pearce" Phil Allison wrote: "Arny Krueger" How does one find that a system has a fault if all the tests you do are constrained from demonstrating that fault? ** This is the exact *dumb***** error Arny the Asshole is besotted with. Amusingly - it is the exact same "error " used constantly by snake oil merchants - the error of applying an unrealistic & unjustified criteria in testing. Any device of any kind will, of course, fail some test - if you make it tough enough. Proves nothing of any value to anyone. It is the *mark* of an good engineer that to devise tests that are indicative of the needed performance in the intended application - not too easy and neither so tough that passing is next to impossible. Fools set up impossible criteria and then pass judgements on how badly the test subjects all fail. Fools. So clearly the ultrasonic stability of an amplifier is a matter of no interest to a design engineer. ** No such idiotic conclusion follows at all from my post. You are a demeted, know nothing ass - Don Pearce. Kindly go **** yourself - again . ** Hey Don - RF and audio are not the same !!! Reflections occur at impedance discontinuities. ** Hey Don - RF and audio are not the same !!! You don't need even a millimetre of cable. ** Hey Don - RF and audio are not the same !!! Any time an impedance changes, power is scattered ** Hey Don - RF and audio are not the same !!! - some goes forwards into the load, some goes backwards into the source. ** Hey Don - RF and audio are not the same !!! The bigger the discontinuity (rom 300 to 100000 ohms, for instance) the more of the available power is scattered backwards. ** Hey Don - RF and audio are not the same !!! That is the basis of Scattering Parameters ** Hey Don - RF and audio are not the same !!! - a standard method of specifying matching, terminating and reflecting. ** Hey Don - RF and audio are not the same !!! Pearce Consulting http://www.pearce.uk.com = a bloody RF web site !!! Don Pearce !! YOU are one, PITA scatterbrained ****ing IDIOT !!!! ............. Phil .......... Phil Well, that one certainly expolded with far more ordnance than I put in. What went bang up your end, Phil? d Don, Don't take Phil too seriously. He's having a bit of an "episode" lately. A quick check over at aus.hi-fi will reveal 99% of the regulars reckon he's headed for a brain meltdown. Clearly Phil knows nothing about impedance mismatch and its effects. He's probably aware that if there is an impedance mismatch it is accompanied by a power loss (probably more by observation than by understanding how it occurs). He just has no idea what happens to the reflected power. His misunderstanding is only further reinforced by the fact that he repeatedly refers to the problem being only related to RF throughout his rantings. Cheers, Alan |
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#98
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"Alan Rutlidge" wrote
in message Don't take Phil too seriously. He's having a bit of an "episode" lately. A quick check over at aus.hi-fi will reveal 99% of the regulars reckon he's headed for a brain meltdown. Headed? Arrived! Clearly Phil knows nothing about impedance mismatch and its effects. Nonsense. He's probably aware that if there is an impedance mismatch it is accompanied by a power loss (probably more by observation than by understanding how it occurs). No doubt. He just has no idea what happens to the reflected power. Nonsense. His misunderstanding is only further reinforced by the fact that he repeatedly refers to the problem being only related to RF throughout his rantings. In the real world it is very much a RF problem. These days if we want to send audio any significant distance (i.e., dozens of miles), we don't send it as audio. It takes signficant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. |
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#99
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"Alan Rutlidge" "Don Pearce" ** How ****ing hilarious !! A desperate, Aussie Arse Bandit tries to alert a desperate, geriatric Pommy Charlatan about being outed as a ****wit !! Keep watching next week folks, for more fun. ......... Phil |
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#101
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On 8/31/05 5:37 AM, in article , "Joe
Kotroczo" wrote: On 30/08/05 15:27, in article , "SSJVCmag" wrote: (...) The 1946 Cocteau original sets a standard for both beauty and technical trickery still seldom approached. (...) Gilliam is the only director that even TRIES for this level of art-in-production. Peter Greenaway? Who? Tell me... |
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#102
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SSJVCmag wrote:
On 8/31/05 5:37 AM, in article , "Joe Kotroczo" wrote: On 30/08/05 15:27, in article , "SSJVCmag" wrote: (...) The 1946 Cocteau original sets a standard for both beauty and technical trickery still seldom approached. (...) Gilliam is the only director that even TRIES for this level of art-in-production. Peter Greenaway? Who? Tell me... Yes. Watch Zed and Two Noughts. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#103
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On 8/31/05 5:37 AM, in article , "Joe Kotroczo" wrote: Peter Greenaway? On 8/31/05 11:01 AM, in article , "SSJVCmag" wrote: Who? Tell me... Just did a little online reading about him...I have homework to do! Great more time I don;t think I have to be carved out of the audio and video drama projects that need herding... Thanks bunches! |
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#104
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On 31/08/05 17:07, in article , "Scott Dorsey"
wrote: (...) The 1946 Cocteau original sets a standard for both beauty and technical trickery still seldom approached. (...) Gilliam is the only director that even TRIES for this level of art-in-production. Peter Greenaway? Who? http://www.imdb.com/name/nm0000425/?...8cG49MHxrdz0xf HE9Z3JlZW5hd2F5fGZ0PTF8bXg9MjB8bG09NTAwfGNvPTF8aHR tbD0xfG5tPTE_;fc=1;ft=32;f m=1 Tell me... Yes. Watch Zed and Two Noughts. Or "Drowning by numbers". -- Joe Kotroczo |
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#105
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The discussion somehow seems to have veered off to the slew-rate
requirements of sampled systems. An interesting topic and relevant to what we do, but the OP asked about slew rates and *mic pre* performance. So we're back to the question: what's the maximum rise-rate of a signal coming from a microphone? What does a mic pre need to put up with? Peace, Paul |
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#106
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Paul Stamler wrote: The discussion somehow seems to have veered off to the slew-rate requirements of sampled systems. An interesting topic and relevant to what we do, but the OP asked about slew rates and *mic pre* performance. So we're back to the question: what's the maximum rise-rate of a signal coming from a microphone? What does a mic pre need to put up with? A good question too. Time for a new thread ? Graham |
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#107
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On Wed, 31 Aug 2005 15:00:57 GMT, SSJVCmag
wrote: I'm considering building a standalone 'sub' based around the left over original K-48. There's an article i want you to see, but it's not on the internet; mail ya a copy tomorrow. You might like it. Always the best, Chris Hornbeck |
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#108
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On Wed, 31 Aug 2005 17:28:57 +0200, Joe Kotroczo
wrote: Yes. Watch Zed and Two Noughts. Or "Drowning by numbers". _The Cook, the Thief, his Wife and her Lover_ got pretty good recognition and deserved it. Chris Hornbeck |
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#109
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#110
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"Paul Stamler" The discussion somehow seems to have veered off to the slew-rate requirements of sampled systems. An interesting topic and relevant to what we do, but the OP asked about slew rates and *mic pre* performance. So we're back to the question: what's the maximum rise-rate of a signal coming from a microphone? What does a mic pre need to put up with? ** Long as the mic pre can output a full level sine at 10kHz it will be free of slew limiting with any natural sound picked up by a normal microphone. If it can do full level out to 20 kHz then it has a nice safety margin. So ( using SR = 2.pi.f.Vp ) a slew rate of 1 to 2 V/uS is the needed spec. The popular IC op-amps are rated at around 10 V/uS. Tube mic pre-amp circuits are NOT likely to exhibit slew limiting since the transformers limit high frequency bandwidth and so hide the effect. .......... Phil |
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#111
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"Arny Krueger" wrote in message ... "Alan Rutlidge" wrote in message Don't take Phil too seriously. He's having a bit of an "episode" lately. A quick check over at aus.hi-fi will reveal 99% of the regulars reckon he's headed for a brain meltdown. Headed? Arrived! Clearly Phil knows nothing about impedance mismatch and its effects. Nonsense. So by that comment can one deduce you know what Phil is thinking? He's probably aware that if there is an impedance mismatch it is accompanied by a power loss (probably more by observation than by understanding how it occurs). No doubt. He just has no idea what happens to the reflected power. Nonsense. So once again, by that comment you know what Phil is thinking? You must be more talented that most would give you credit for.  However just in case the above is not true, perhaps you can enlighten the group as to what happens to that energy which is not fully absorbed due to impedance mismatch? His misunderstanding is only further reinforced by the fact that he repeatedly refers to the problem being only related to RF throughout his rantings. In the real world it is very much a RF problem. No disagreement there Arny. But impedance mismatch and its effects at lower frequencies are not superfulous. The local power company will tell you another story and (in your country) the propagated frequency is a mere 60Hz. (no where near RF) These days if we want to send audio any significant distance (i.e., dozens of miles), we don't send it as audio. Agreed, however the laws of physics don't change simply because you lower the distance. It takes signficant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). Cheers, Alan |
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#112
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"Alan Rutlidge" "Arny Krueger" It takes significant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). ** ROTFLMAO !!!! Does this Rutmaniac, ****ing idiot actually teach such monumental **BULL****** to IT industry trainees ???? Only the dullest teenagers would fall for such utter ****e !!! FYI Telecommunications data is digital ( not audio) and travels to places like India via optical fibre and geo-stationery satellites - not thousands of miles of bloody co-ax !! What a complete MORON !!!! ........... Phil |
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#113
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On Thu, 1 Sep 2005 17:25:01 +1000, Phil Allison wrote:
"Alan Rutlidge" "Arny Krueger" It takes significant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). ** ROTFLMAO !!!! Does this Rutmaniac, ****ing idiot actually teach such monumental **BULL****** to IT industry trainees ???? Only the dullest teenagers would fall for such utter ****e !!! FYI Telecommunications data is digital ( not audio) and travels to places like India via optical fibre and geo-stationery satellites - not thousands of miles of bloody co-ax !! What a complete MORON !!!! .......... Phil So Phil. It is digital right up to the phone at the far end, is it? That phone doesn't have a hybrid transformer, does it? That transformer doesn't have a limited sidetone spec, does it? The match of phone to line is perfect is it? There is no signal reflection from that phone, is there? That reflected power isn't digitised by the codec is it? That digitised signal isn't audible at the sending end as an echo is it? And the fact that these signals might use satellites or optical fibre somehow magically makes all these reflected signals disappear, does it? Only only planet Phil does the world work this way. d |
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#114
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MESSAGE BY PHIL (LUNATIC, VULGAR, TROLL) ALLISON
RE-POSTED TO APPROPRIATE NEWSGROUP On Thu, 1 Sep 2005 17:25:01 +1000, "Phil Allison" wrote: "Alan Rutlidge" "Arny Krueger" It takes significant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). ** ROTFLMAO !!!! Does this Rutmaniac, ****ing idiot actually teach such monumental **BULL****** to IT industry trainees ???? Only the dullest teenagers would fall for such utter ****e !!! FYI Telecommunications data is digital ( not audio) and travels to places like India via optical fibre and geo-stationery satellites - not thousands of miles of bloody co-ax !! What a complete MORON !!!! .......... Phil |
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#115
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"Don Pearce" ** Snip ****ing idiot questions. Only only planet Phil does the world work this way. ** Err - the way the Don said. ........... Phil |
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#116
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"Harry Houdini" wrote in message ... Trying to get a handle on this Slew Rate spec you often see published for higher-end mic pre's. Please correct me if I'm wrong, but from what I've read, it seems that a preamp with higher slew rate is more likely to capture transients better and hopefully render a more detailed soundstage. Is this true? Why not do the calculations yourself? Work out the maximum peak-to-peak voltage of the pre-amp output, and the maximum frequency you want to capture. Multiply the two to get the required slew rate in volts per second; divide by a million to get the required slew rate in volts per microsecond. So, suppose the max output is 3 volts RMS. That's about 8 volts peak-to-peak. And support the highest frequency is 1,000,000 HZ (!). So, the required slew rate is 8 volts per microsecond. Tim .. .. |
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#117
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"Don Pearce" wrote in message .. . On Thu, 1 Sep 2005 17:25:01 +1000, Phil Allison wrote: "Alan Rutlidge" "Arny Krueger" It takes significant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). ** ROTFLMAO !!!! Does this Rutmaniac, ****ing idiot actually teach such monumental **BULL****** to IT industry trainees ???? Only the dullest teenagers would fall for such utter ****e !!! FYI Telecommunications data is digital ( not audio) and travels to places like India via optical fibre and geo-stationery satellites - not thousands of miles of bloody co-ax !! What a complete MORON !!!! .......... Phil So Phil. It is digital right up to the phone at the far end, is it? That phone doesn't have a hybrid transformer, does it? That transformer doesn't have a limited sidetone spec, does it? The match of phone to line is perfect is it? There is no signal reflection from that phone, is there? That reflected power isn't digitised by the codec is it? That digitised signal isn't audible at the sending end as an echo is it? And the fact that these signals might use satellites or optical fibre somehow magically makes all these reflected signals disappear, does it? Only only planet Phil does the world work this way. d Don, Fair go mate.(wink) You don't honestly thinks a toaster repairman needs to know much about impedance mismatch do you? :P Oh, and it looks as if I've been elevated from wire tugging status to Information Technologist virtually overnight. Phil could never get hislies straight - err no pun intended.. You know, one of these days he'sactually gonna get something right about me. When that happens I'll duck out and by a lottery ticket. Cheers, Alan |
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#118
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"Tim Martin" Why not do the calculations yourself? ** Indeed - a very good idea. Work out the maximum peak-to-peak voltage of the pre-amp output, and the maximum frequency you want to capture. Multiply the two to get the required slew rate in volts per second; divide by a million to get the required slew rate in volts per microsecond. So, suppose the max output is 3 volts RMS. That's about 8 volts peak-to-peak. And support the highest frequency is 1,000,000 HZ (!). So, the required slew rate is 8 volts per microsecond. ** For a sine wave: SR = 2.pi.Vp.F So SR = 26.6 v/uS For a 8 volts p-p triangle wave (ie slew limited sine wave) SR = 4.Vp.F = 16 v/uS ( When it comes to numbers, never trust other's cooking ) ........... Phil |
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#119
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"Alan Rutlidge" Phil Allison ** ROTFLMAO !!!! Does this Rutmaniac, ****ing idiot actually teach such monumental **BULL****** to IT industry trainees ???? Only the dullest teenagers would fall for such utter ****e !!! Oh, and it looks as if I've been elevated from wire tugging status to Information Technologist virtually overnight. ** A ****wit, wire tugger is all you are - Arse Bandit. Falsely impersonating an IT instructor is what you do. Chasing under aged boys around Thailand notwithstanding. You know, one of these days he's actually gonna get something right about me. ** Been doing just that for a very long time. No surprise that a congenital LAIR & a criminal Arse Bandit would never agree. ........... Phil |
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#120
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"Alan Rutlidge" wrote
in message "Arny Krueger" wrote in message ... "Alan Rutlidge" wrote in message Don't take Phil too seriously. He's having a bit of an "episode" lately. A quick check over at aus.hi-fi will reveal 99% of the regulars reckon he's headed for a brain meltdown. Headed? Arrived! Clearly Phil knows nothing about impedance mismatch and its effects. Nonsense. So by that comment can one deduce you know what Phil is thinking? I've probably got more experience with Phil than most, so I know what he once knew. He's probably aware that if there is an impedance mismatch it is accompanied by a power loss (probably more by observation than by understanding how it occurs). No doubt. He just has no idea what happens to the reflected power. Nonsense. So once again, by that comment you know what Phil is thinking? No, I know what he has known. You must be more talented that most would give you credit for. It's about years of experience with Phil. However just in case the above is not true, perhaps you can enlighten the group as to what happens to that energy which is not fully absorbed due to impedance mismatch? I object to the use of words he "fully absorbed due to impedance mismatch". In fact no energy is absorbed by an impedance mismatch. An impedance mismatch reallocates energy which should be absorbed someplace else. His misunderstanding is only further reinforced by the fact that he repeatedly refers to the problem being only related to RF throughout his rantings. In the real world it is very much a RF problem. No disagreement there Arny. But impedance mismatch and its effects at lower frequencies are not superfulous. The local power company will tell you another story and (in your country) the propagated frequency is a mere 60Hz. (no where near RF) Yeah, but the transmission lines are a tad long by normal audio production standards. These days if we want to send audio any significant distance (i.e., dozens of miles), we don't send it as audio. Agreed, however the laws of physics don't change simply because you lower the distance. Agreed. But those same laws of physics say that audio over reasonable distances isn't a problem, and in the real world it isn't. It takes signficant distances for audio electrical signals to demonstrate things like reflections and standing waves. For most practical purposes, they never happen because by the time the audio goes that far in the modern world, its probably already been digitized. Digitising an audio signal does not eliminate propagation delay if the signal is transmitted over a long distance. Of course not. And the higher frequencies make things like impedance matching much more important. To demonstrate this in combination with the problem of impedance mismatch - make an international telephone call to a third world country like India. The echo you hear is usually 100% attributable to poor impedance mismatch at the other end of the line. And guess what? It's all occurring at audio frequencies (300Hz to 3400Hz). Been there done that, different location - namely Army in Germany during the late 60s. |
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