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In Reply to: RE: Are shielded cables declasse? posted by robfoto@sbcglobal.net on May 30, 2008 at 21:50:32
To extract every bit of detail (pun intended) from a well-recorded Redbook CD, you need cables that are both shielded and damped. Shields reduce noise, but can inject their own artifacts if they are not damped against electromagnetic resonance.
I've only recently begun to understand how tricky this is, so I recommend avoiding shielded cables in most cases.
Braiding is also tricky, and can make things muddy if done incorrectly. Simple twisted-pair of good wire will preserve most of the fidelity in most cases.
Yes, the Monster cables may be damaging your signal. If your preamp has sufficient drive, you need shielding even less at its output.
Follow Ups:
I have not found shielded cables to outperform well constructed unshielded cables. I too find a reduction in dynamics and air with shielded designs...
HowdyPardon my ramble, but bear with me:
I have way too much gain in my system in that I can turn it up about 30dB louder than too loud, however this allows me to hear the noise earlier in my system pretty well if I pause my sources or (carefully) use a track with extremely low levels. When I turn my system to full volume and invite my wife or daughter to listen right at the tweeters I have just a minute amount of white noise so I'm guessing that my unshielded cables are doing great at reducing the noise pickup in my system. (I have in the past had much more colored noise under these circumstances and have explicitly addressed the issues so uncovered.)
Every type of shield I've used (from very small amounts of ESR paper to cables with a little graphite to cables with more, to explicitly shielded cables to coax for speaker wire, etc.) all mess at least with the macro and micro dynamics of the music and with the overall coherence if not also explicitly rolling of the highs loosing air, etc.
Don't get me wrong: I know that there are a lot of systems which are quite sensitive to RFI, EMI, that are microphonic in various places (including their cables) and that almost everyone of your posts is correct when talking about those systems.
However there are also systems that are better designed which are less sensitive to these forms of interference, still are resolving and detailed and yet are very engaging. Hence I think that at times you overgeneralize.
I have no qualms saying my system is one such system because I can hear differences in cables, mechanical isolation, power cords, etc. as well as that I've visited many other people's houses, shows, etc. and can comfortably say that with the exception of one other inmate's system (and then only sometimes) mine has the most resolution I've heard.
This is in part why I've invited you over on the past (tho I know that most people don't have the time or inclination to visit a pig in a poke system :) One reason is that it's always fun to have visitors (and to visit others) and another is that it's always fun to see how other paths lead to systems that are just as enjoyable as our own.
I'm not claiming my system is perfect, far from it. But most of your posts (tho correct for many systems I've encountered) are so far off of the mark for a few systems I've encountered that I have to speak up now and then :)
-Ted
RF noise is not directly audible, even by a teenager :). It affects the audio signal through intermodulation, so it is silent when the signal is zero. A small amount of it adds apparent sparkle and a sense of air, as well as enhanced punch on plucked strings and struck cymbals. However, it obscures the microdynamics that give Ella Fitzgerald, for example, her characteristic vocal texture, or allow the differences between cymbal tones to be savored. Someone (such as me) familiar with a well-tweaked setup incorporates these system behaviors into a notion of the baseline performance. The only way to know they are there is to hear the system with them removed. What I'm trying to get across is that your system may be better than you can possibly imagine.
One component of the RF noise environment is the spectrum of tones produced by resonant objects in the audio system. These objects may be cables and power cords as well as parts of the speaker crossover networks or wiring. One particular type of resonant object comprises the shields on shielded cables and cords. While they may function to reduce audio band noise, they act to increase the RF noise environment by resonating unless measures have been taken to damp them.
This is why many folks with refined systems do not find shielded cables useful. They do not have strong sources of audio band noise, so the only action of the shields is to degrade the signal. I'm not going to go into the details of what it takes to properly damp shields because a lot of the information is proprietary to others.
Unshielded and undamped cables act as transmitting and receiving antennas for RF noise. An audio system using them could achieve complete Redbook resolution if the connected equipment were sufficiently insensitive to the RF noise, including the resonant tones, present on the cables. I don't think any such equipment exists, but the trend in behavior reported in published reviews of ultra-expensive equipment suggests to me that designers are working in that direction.
I appreciate your invitation to hear your system. I don't travel much, but would let you know if circumstances lead me to the Seattle area.
HowdyPerhaps I misunderstood you post.
I saw: "To extract every bit of detail (pun intended) from a well-recorded Redbook CD, you need cables that are both shielded and damped." which seemed pretty unambiguous.
But perhaps you meant it to be read with your subject: "Only for lower-resolution systems to extract every bit of detail (pun intended) from a well-recorded Redbook CD, you need cables that are both shielded and damped."
Anyway, yes, I understand the distinction you are making between RF noise and audio band noise and I also understand a lot of the many ways they interact in practical systems. However I still stand by my statement that there are well designed systems that aren't nearly so twitchy as apparently many posters here are subject too.
In fact one might state: "if you can't hear how a shield deleteriously affects your audio your system isn't very revealing" I know that this isn't really true in general but it's at least as true for many systems I know as my reading of your first post.
-Ted
P.S. Perhaps if I get down your way I visit you, Bart and/or some of your friends.
Most commercial CDs have less than the maximum resolution allowed by the format. A few reveal increasing recorded details with improvements in noise reduction techniques in highly resolving systems. One of these techniques involves how the cable shields are damped. Incorrectly damped shields will harm the signal, and do more proportional harm in highly resolving systems than in more modest systems.
The problem is that these improvements are subtle and easily confounded with the basic tonal balance. As I wrote above, some degree of RF noise pollution sounds like added sparkle, air, and punch. Removing it makes the system sound dull. The additional true detail only becomes apparent after prolonged listening. If the system's tonal balance had been selected based on some amount of RF noise, the system will remain dull with the noise removed. Rebalance may be expensive, as it may require new speakers, etc.
I realize there are pleasing and highly resolving systems that use unshielded cables. My assertion is that they could be even more resolving (and more pleasing, if such resolution is to the taste of the listener) if the cables were properly shielded and damped. Simply adding shields without attention to the damping will not, in my understanding of the issues, guarantee increased satisfaction, and will likely decrease satisfaction. We nearly agree on your comment, "if you can't hear how a shield deleteriously affects your audio your system isn't very revealing," but I would only add 'an undamped' to the word 'shield.'
Let's see: damping involves the introduction of lossiness. In a mechanical system, that would call for a shock absorber. In an electrical system, resistance would be needed. But how to introduce resistance into a shield? Interrupt the shield every few inches and solder a resistor from one section to the next?
Hmm, maybe not. How about a resistor between shield and center conductor every few inches. It would load down the source, though. Okay, resistors between shield ground and chassis ground? With a third wire to carry the chassis ground?
The extracted energy is dissipated and converted to heat.
Ohmic resistance is involved, but not necessarily resistors.
Further details are proprietary to others and not mine to share.
Hmm, mayba a conductive, but lossy, carbon-impregnated shield?
Hey, how about carbon nanotubes? Just a wild guess, but it sounds classy!
Howdy
Some carbon shields may work (I don't know), but some certainly take the dynamics out of the music.
-Ted
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Removing it makes the system sound dull. The additional true detail only becomes apparent after prolonged listening.
I find that one can hear more detail at lower levels with a well shielded system. You don't have to crank them. Everyone (especially the Hornies) talk about dynamic range, but usually refer to the loud end. Exploring the bottom of the range can be equally satisfying to me.
rw
The details are at the lower end of the dynamic scale. My visual analogy is that improving the lower-end dynamics is like turning up the lights at the back of the stage.
HowdyThat's what I thought you meant. And to beat a dead horse I disagree at least in the context of some systems. In fact I really don't think you can improve my system with any kind of cable shielding... There simply isn't any of the sound of RF artifacts that you describe here or any of your other posts, yet I get amazing amounts of detail without fatigue. I have spent a lot of time making sure that I don't have any fatiguing symptoms since my system is on 24/7 and playing sound probably 20 hours/day on average. (Now that I'm married I don't sleep in front of it anymore, but I used to :)
Don't get me wrong I'm not trying to generalize my experience and say that properly built shielded cables don't exist, but in my experience they appear to be as rare as systems that don't need them are in your experience :)
I tend avoid any changes to my system that mess with the tonal balance, it both sounds right and measures well (at least with a crude 1/3 measurement. Someday I'll either write or borrow a good spectrum analyzer for measuring my room more accurately, but it's fine for now and I have higher priority work to do.)
Perhaps you haven't looked at my profile to see what speakers and other equipment I have as well as you might have missed my room treatments... With amps flat to 200kHz, speakers flat to 40kHz (or is it 50kHz?), and silver speaker wires and interconnects some might think my system would be bright or etched, but far from it. It's appropriately smooth top to bottom.
Believe me I can hear/measure the effects of RF in my room. (Tho my scope only goes to 200MHz I've been measuring things enough to have a pretty good idea what's happening up to there...) In other situations (my older office system or in the store where I bought a lot of my components) I could easily hear when people's cell phones were receiving a message before they plinged, etc. and could tell when people were downloading on the computers in the next office... In my old house I had to move components around to avoid the interference from my old Sony Wega: it had horrible fields about 6" directly under it rendering the top shelf Tivo/video/UPS land, not audio land. Different Tivos are built quite differently, some have horrible ground loop issues and others are clean as a whistle. Some have noisy disk drives, others are quiet. The fans are all over the map.
It used to matter what time of the day I played my system, but that's long behind me, it's clear, clean and engaging any time of day or night. These kinds of fixes (find a problem, measure it, do some research if necessary, design a fix, measure that, iterate) for various problems have left me with confidence that I'm not (in general) chasing my tail and that (also in general) I have a good idea what's going on in my system. I have explicitly not addressed some known issues because I don't like any fix that's avaiable, but these are more like room issues...
I'm rambling so I'll stop. I just had to engage you on this topic at least once :)
-Ted
do not yet exist to my knowledge.
I should have made that clear at the beginning to avoid some misunderstanding.
The ones I know about are still under development, and may never get to the point where the designer is happy with them. What I've heard along the way, though, is what motivated my bald assertion regarding resolution and shielding.
I'm glad you are happy with the performance of your system, but I don't agree that it is entirely free of RF noise artifacts. I have too much experience with confounding the subtle effects of RF noise with system balance.
Howdy
Ah..
Well I'd like your personal assessment here sometime, but I know that's impractical.
Still presuming I'm still subject to some degree of RFI, my experience is clear that any shielding whatsoever has clear effects on the audio band so till I hear with my ears otherwise it's clear to me that shielding throws the baby out with the bathwater: any positive effects (which I doubt in my system) are clearly overwhelmed by the negative effects.
Does your associate need a discreet beta tester? :)
-Ted
:(
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