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In Reply to: RE: The distinction is between RF noise and audio band noise. posted by Ted Smith on June 01, 2008 at 20:14:00
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.'
Follow Ups:
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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