CRT monitor for PC processes up to 150MHz video bandwidths. Is it "low frequency"? :-(
Low and high frequency to a first order is a function trace length divided by the wavelength of the highest frequency present.
If the video bandwidth is say 150Mhz (say 1.5m at 0.6 Vf) then to avoid needing to treat things as transmission lines, features should be shorter then about 15cm.
Thus the cable in this case is a transmission line, and will be terminated at a buffer on the board with a 75 ohm input impedance, however, paticularly if series terminated at the source, a few cm of connector and track between the end of the cable and the video buffer do not particularly need to be an accurate 75 ohms.
Note that something like a 150Mhz pixel clock will have an edge rate in the low Ghz, and so will have much tighter constraints then a 150Mhz video bandwidth analogue signal will.
For a pcb track to be 'very low impedance' it needs to be short compared to the wavelength so that it can be considered as a lumped constant network, if it is not short compared to the wavelength then it must be considered a transmission line and those are seldom 'very low impedance', at least not if you want to fit a sane number on a board of reasonable density.
This is transmission lines 101 and Terman, Langford smith, and any communications systems undergrad text covers it.
Regards, Dan.
If the video bandwidth is say 150Mhz (say 1.5m at 0.6 Vf) then to avoid needing to treat things as transmission lines, features should be shorter then about 15cm.
Thus the cable in this case is a transmission line, and will be terminated at a buffer on the board with a 75 ohm input impedance, however, paticularly if series terminated at the source, a few cm of connector and track between the end of the cable and the video buffer do not particularly need to be an accurate 75 ohms.
Note that something like a 150Mhz pixel clock will have an edge rate in the low Ghz, and so will have much tighter constraints then a 150Mhz video bandwidth analogue signal will.
For a pcb track to be 'very low impedance' it needs to be short compared to the wavelength so that it can be considered as a lumped constant network, if it is not short compared to the wavelength then it must be considered a transmission line and those are seldom 'very low impedance', at least not if you want to fit a sane number on a board of reasonable density.
This is transmission lines 101 and Terman, Langford smith, and any communications systems undergrad text covers it.
Regards, Dan.
I have provided numerous links to the likes of Howard Johnson, Eric Bogatin etc., on this and other threads where we have discussed these things, as well as others such as Dmills and DF96 to name a couple, yet these links to further information seem to be ignored? Is this because they would take the magic out of playing with this stuff, and instead use engineering practices to either get things right or realise there are more critical things to worry about in audio reproduction?
What I was wanting to mean is that the name "digital cable" is wrong. Digital nothing, analog nothing.
You can build a reasonably good linear audio amplifier using a typical "digital inverter" CD4069, 74HC04 simply providing DC feedback via a high value resistor from output to input and configuring it as an analog amplifier, and taking input and output AC coupled. I tried them for a electret mic amp and it is surprising. I saw them in an old National Semiconductors blue CMOS book.
As a counterpart, an opamp can be used in "digital mode" using some positive feedback and placing it as a hysteretic amplifier.
Again, digital nothing, analog nothing. Simply a cable‼
You can build a reasonably good linear audio amplifier using a typical "digital inverter" CD4069, 74HC04 simply providing DC feedback via a high value resistor from output to input and configuring it as an analog amplifier, and taking input and output AC coupled. I tried them for a electret mic amp and it is surprising. I saw them in an old National Semiconductors blue CMOS book.
As a counterpart, an opamp can be used in "digital mode" using some positive feedback and placing it as a hysteretic amplifier.
Again, digital nothing, analog nothing. Simply a cable‼
Well DF96 being that I'm not technically-oriented. Much of this article was beyond my scope of understanding. Still I try to read, learn and understand what I can. So yes, I did understand there's noting "magical" about using a 1.5M digital wire. If I understood what Steve was saying; a 1.5M wire will work best the majority of the time not because it's a magic number, but rather because much of today's digital gear is not being built to stringent enough tolerances! Thus using a 1.5M wire is an easy fix to many of the problems these loose tolerances cause. Or did I misunderstand that too?
Thetubeguy1954 (Tom Scata)
The 1.5m (not 1.5M) cable assumes:
1. Steve's idea is correct - I'm not sure it is.
2. A particular cable velocity factor - depends on the cable.
3. A particular signal rise time - depends on the electronic design details and what, if any, steps have been taken to deal with EMC issues.
Thus a 1.5m cable does not necessarily 'fix' anything, even if his idea is correct which I believe is not the case. You can safely ignore that article. I suspected you did not understand it; thanks for confirming this.
1. Steve's idea is correct - I'm not sure it is.
2. A particular cable velocity factor - depends on the cable.
3. A particular signal rise time - depends on the electronic design details and what, if any, steps have been taken to deal with EMC issues.
Thus a 1.5m cable does not necessarily 'fix' anything, even if his idea is correct which I believe is not the case. You can safely ignore that article. I suspected you did not understand it; thanks for confirming this.
Hi AmpUtator! Now that sounds like an outstanding deal. Especially with the DH Labs having a silver-coated center conductor too.
I know many in the specs & measurements camp will think I'm foolish. But I'm looking at the Oyaide FTVS-510 5N Silver Coaxial Cable. The conducting center wire is: 1.05mm 5N (99.9995%) pure silver. The insulation is: FEP skin layer & foamed polyethylene. The shield is comprised of copper foil & silver plating braided copper. The outer sheat is: UV coating polyurethane and it has an impedance of 75Ω. It's capacitance is: 56.5 nF/Km. The attenuation is: 23.1 dB/Km. With a resistance of 21Ω/Km and a diameter of 8.0mm.
My main reason for wanting to purchase the Oyaide FTVS-510 5N Silver Coaxial Cable is it's usage of 5N pure silver as the center conductor wire.
That was very important to me. I know for a fact that I can detect audible differences between copper & a silver ICs when they're inserted between my amp & my transport. But in that position the wires are carrying analogue signals. I want personal experience using both silver & copper coax ICs to see if using different metal as a conductor affects the sound audibly when they're carrying a digital signal. And to gain that personal experience I simply MUST listen for myself and see if I can also detect any audible differences between a silver coax wire & a copper coax wire when they're placed between my transport & DAC!
The only downside to this experiment is the Oyaide FTVS-510 5N Silver Coaxial Cable cost $90. So if anyone knows where I can purchase a solid silver center conductor coax wire cheaper for my experiment. Please let me know, ok?
Thetubeguy1954 (Tom Scata)
What is a "digital cable", one which when there is a 1 in somewhere place the cable exists and when 0 doesn't? In any case, a "digital cable" in which form is different from an analog one?
That's shorthand for a cable that is optimized for digital audio signals.
One major cable manufacture makes more than 40 different RG-6 cables.
Some are optimized for:
Sunlight resistance.
Fire Safety.
Being buried in dirt.
Low cost.
Hanging from pole to pole.
Flexibility.
Cable TV channel signals.
Long analog audio cables.
Oh yes some are optimized for digital audio
Hi Tom,
If you want a lower price silver cored cable try the Audioquest VSD-5 from the Ebay..
http://www.ebay.com/itm/Audioquest-...les_Adapters&hash=item53eff2c126#ht_491wt_646
Quite good sounding as well... but I still prefer the Oyaide a bit more.
If you want a lower price silver cored cable try the Audioquest VSD-5 from the Ebay..
http://www.ebay.com/itm/Audioquest-...les_Adapters&hash=item53eff2c126#ht_491wt_646
Quite good sounding as well... but I still prefer the Oyaide a bit more.
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How would a silver conductor make any difference over a copper conductor carrying digital signals? I would be interested in any mechanisms that may be at play here, as I am puzzled and can not think of or simulate any difference between the two metals (apart from a tiny difference in resistivity and its inverse conductance).
Further to the article regarding the cable lengths, why does he change the units used for length between paragraphs.
Also why do the some prefer to quote and use an obviously flawed and audiophile based article instead of doing real research into the problem and look at the many scholarly articles presented on the web by real experts in this field, and get an understanding into the real issues. And more importantly how (if there is a problem, and it is a BIG IF) how to solve them scientifically and not have to resort to applied magic.
http://www.ddpp.com/DDPP4student/Supplementary_sections/Zo.pdf
Further to the article regarding the cable lengths, why does he change the units used for length between paragraphs.
Also why do the some prefer to quote and use an obviously flawed and audiophile based article instead of doing real research into the problem and look at the many scholarly articles presented on the web by real experts in this field, and get an understanding into the real issues. And more importantly how (if there is a problem, and it is a BIG IF) how to solve them scientifically and not have to resort to applied magic.
http://www.ddpp.com/DDPP4student/Supplementary_sections/Zo.pdf
Tom, google how coaxial cable works. It is not the way how analog signals from source to preamp transmited. And important not only center conductor with lowerst possible resistance, but cable construction, termination = how it is good as transmission line, what maximum bandwidth it allows, rathen then materials itself.
In selection of top-performing coax cable for SPDIF you probably can find, that cables in range 100...500$ can sound different, but you hardly select which one is better. If you compare 5$ cable vs >100$ cable you definitely find that 100$ cable is better.
In 100-500$ range: there are a lot of marketing
Does not mean then 500$ cable guarantee best performance. If you searching ultimate cable for you system and it is the last what you cab improve there - loan and try them at home.
And coincidentally, you just happen to sell this stuff. It is fortunate for you that most audiophiles are ignorant of basic transmission theory and signal integrity and that they have no desire to gather any expertise in that area (this despite the efforts of those with actual expertise trying to carefully explain things, and including references).
Anything more than about $10 is for psychology, not actual sound.
Anything more than about $10 is for psychology, not actual sound.
Or a crazier idea: look at the analog output. After all, that's the only part that actually matters. I mean, seriously, this stuff is like trying to affect a car's 1/4 mile time by playing with exotic materials for the gas cap. If you want to convince yourself that the gas cap indeed has nothing to do with it, measure the 1/4 mile time.
Eye pattern is a good way to see how much "safety margin" you have - but in most cases it will just show that you have enough and the cable works. As SY stated, the only real test is to measure the end result.
Not questioning your statement, just curious about how you know that for a fact....
BTW,
Much thanks for the info. Starting with the Audioquest-VSD-5 definitely seems like the way I should go ---FOR NOW! My reasons for choosing to purchase the Audioquest-VSD-5 first are quite logical...
- This has opened a completely new area of audio for me. Previously I only used a CD player. So I've never had the opportunity to test myself on an audio system I'm intimately familiar with.
- I need to determine if I can detect audible differences between copper and silver wires inserted between a transport & DAC. As easily as I can when copper & silver wires are carrying analogue signals between my DAC & integrated amp.
- Since I have no idea if I can or cannot detect audible differences ---{if there are any}--- in IC wires of different metallurgical make-up when they're carrying digital signals. Why would I spend BIG bucks on silver ICs until I know the answer to that question?
Thetubeguy1954 (Tom Scata)
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