How essential is shielding?

The DNM reson IC configuration strongly resemble 300 ohm twin lead antenna wires. Wouldn't surprise me if they can act like antenna and pick up certain RF noise emitted by the amps perhaps. The nise exists with amps on and pre-amp off and resembles multipath noise one often picks up with FM stereo tuners. Probably not EM the more I think about it, though the buzz in the phono step up rig I eliminated with mu-metal was.

Mapman - who knows? It is a little like ghost chasing. I'm in this business (designing electronics) for a very long time (32 years) finding something strange every single day.

I once had problems with noise in my phono system so I ended up bringing my table to the dealership. At the dealer, the noise problem did not occur, but, the dealer noted that the phonocable was unshielded. He had a cable that was supposedly identical, except that it was shielded (both made by Kimber). It turned out that the shield cable solved the noise problem. I asked the dealer why he sold me the table with the unshielded cable, and we ended up doing a comparison. The unshielded cable sounded better--more open on top, and greater ease in hearing subtle detail. He said he always starts with the unshielded cable and only goes to shielded when noise intrudes.

"It is worth to mention that EMI pickup of lower frequencies such as approx 500kHz generated by many class D amps can be picked-up as direct connection thru capacitance (important to keep wires apart or right angle) and not thru the electromagnetic pickup"

I wonder if this accounts for the intermittent low level high pitched whine I get on occasion with DNM Reson ICs from ARC tube pre-amp to BC ref1000ms? The pitch seems to change with exact location/orientation of the ICs. Not sure if position of the two ICs relative to each other is the determining factor or not.

I switched in a pair of MIT ICs with network boxes the other day and that appears to have eliminated the noise issue for now. I'm waiting to see if it continues in that the issue has come and gone mysteriously in the past for no clear reason.

What are your thoughts on (Synergistic´s) active shielded cables?

Hasse - I owned Synergistic's top-of-the-line Apex interconnects for a few months. At least for me, Synergistic's active shielding worked as advertised. With the Apex cables in the system, backgrounds became spooky quiet.

I didn't keep them because, in my system, they didn't have a natural tonal balance. Of course, YMMV.

Bryon

Hasse, Active shielding means placing buffered common mode signal back on the shield thus reducing capacitance and therefore pickup. It is technique widely used in low level amps like EKG amps but Synergistic's definition is different. They just claim putting battery on the shield. Battery with high voltage is used by Audioquest to polarize dielectric (dipoles) and make it sound the best even if not used for a while (no break-in). Synergestic is a little vague on this.

"What are your thoughts on (Synergistic´s) active shielded cables?"

Very high tech and very expensive.

I'd have to hear them to make any value judgement.

Personally, I prefer an effective shielding approach that is not active, like mu metal, which I already use to good effect to shield my phono step-up device and ICs from external noise inducing EM fields.

FWIW my Audioquest CV6 speaker wires use a similar but lower tech and cost active approach with their DBS devices. These speaker wires are very good but I have not been able to determine how much DBS has to do with it.

Of course, low level ICs and speaker wires are two different beasts as well to start with.

What are your thoughts on (Synergistic´s) active shielded cables?

I have found it can make a difference in noise levels in some cases and not in others.

You have to experiment to determine.

Orientation and position relative to other wires with current passing through or powered devices with transformers that emit EM fields matters a lot.

Capacitance of many typical Belden cables run in order of 25pF per foot while the best interconnects go as low as 3.5pF/ft thanks to use of expensive dielectrics (foam Teflon) and special geometries (oversized tubes). Cable with no shield eliminates hot-to-shield capacitance but hot to return wire capacitance exists and most likely is increased because unshielded wires tend to be twisted pairs. Twisting two wires exposes them to EMI evenly, working effectively as a shield (both for radiating and receiving) but unfortunately increases wire to wire capacitance.

Shielding itself is a very complicated business. For instance, shield made of non magnetic material does not protect against EMI (it cannot) but induced high frequency interference travels on the outside of the cable - a shield, because of skin effect. Add multiple shields + shield's inductance + twisting + additional returns and you'll get something nobody can understand. If it sounds good in your system go for it and don't worry about the science. Noise pick-up is system, and not the cable, dependent - all components participate.

It is worth to mention that EMI pickup of lower frequencies such as approx 500kHz generated by many class D amps can be picked-up as direct connection thru capacitance (important to keep wires apart or right angle) and not thru the electromagnetic pickup. It is because of lenght of the wires that would have to be hundreds of feet long to be any antenna for transmitting or receiving. Antenna works quite well at 1/4 wavelength but drops rapidly below that becoming practically ineffective below 1/10 of wavelength.

As for balanced being remedy - it works but problem starts at high frequencies where noise gets thru transformer capacitance (if used) or instrumentation amplifier (if used instead of transformer) rectification effect (uneven slew rates going up and down cause extraction of the modulation of the signal)

...the Speltz is a tightly wound small gauge wire with a no-see-um negative wire running through. Being as the two carriers are at an almost right angle to each other, I think they would be more influenced by external electromagnetic forces rather than self contaminating.

Hi Muralman - I wasn't trying to say anything about the design of the Anticable I/Cs, or their vulnerability to internal/external noise. Sorry if that was unclear.

I was trying to say that, like you, I have some shielded cables (digital interconnects, power cables) and some unshielded cables (analog interconnects, speaker cables), and that this arrangement, at least in my case, results in a system that is more or less dead quiet. So I was trying to suggest that shielding some cables, but not others, might be an effective way to reduce inter-cable contamination (e.g., power cables to interconnects, or vice versa), without having to shield everything.

Bryon

Bryon, as you know, the Speltz is a tightly wound small gauge wire with a no-see-um negative wire running through. Being as the two carriers are at an almost right angle to each other, I think they would be more influenced by external electromagnetic forces rather than self contaminating. What do you think?

My SCs are purposely run separate from each other.

No, I don't think any such generalizations can be made, Bryon. Many shielded interconnects having low or very low capacitance are available from Cardas, Nordost, and Blue Jeans, among others. Unshielded interconnects with similarly low capacitance are available from Kimber and Nordost, among others.

That's what I figured, Al. Otherwise life would be too simple.

How to know if a cable is shielded.
Well, usually you can just LOOK at a picture of the cable. Most interconnects that are shielded are coaxial, a smooth round cross section. Most non-shieded are just wires, usually woven or twisted together.

Elizabeth - Although this is often true, like with the Kimber PBJ you mentioned, it's worth noting that some unshielded interconnects still have sleeving, and so don't have the appearance of bare wires. Morrow cables are an example.

All of my power cables are fully shielded with shield grounded. That is absolutely necessary for the amps I am using. All other wires are completely bereft of any insulation save for 2 ml.

Muralman - Having some cables shielded but not others seems to me to be a good compromise, since, for any 2 cables that are close enough to potentially contaminate each other, it seems like only one of them would need to be shielded to prevent it. My system has a similar arrangement, but I arrived at it more or less by accident.

Bryon

Are there any generalizations about the typical effects of shielding on cable capacitance? Does shielding increase capacitance?

No, I don't think any such generalizations can be made, Bryon. Many shielded interconnects having low or very low capacitance are available from Cardas, Nordost, and Blue Jeans, among others. Unshielded interconnects with similarly low capacitance are available from Kimber and Nordost, among others.

The reason I cited those particular examples, btw, is that they come to mind as manufacturers who provide complete specs. It's unfortunate that a lot of other manufacturers don't do that.

I should add, btw, that my statements about the importance of capacitance pertain only to interconnects, not to speaker cables, where it is generally an unimportant parameter. Inductance can be important in a speaker cable. If it is high it can sometimes limit upper treble extension to a perceptible degree, especially with speakers whose impedance at high frequencies is low (electrostatics being notable examples).

Best regards,
-- Al

All of my power cables are fully shielded with shield grounded. That is absolutely necessary for the amps I am using. All other wires are completely bereft of any insulation save for 2 ml.

I make my own SCs, and they are very thin 12 gauge ribbons. Stranded and round solid just don't sound right.

Al - In my last post, I should have wrote: Does shielding INCREASE capacitance?

Bryon

How about a list of non-shielded cables?

...how would you isolate the general characteristics directly due to shielding, or lack thereof?

Tholt - I agree with you that the best way to know this would be to have two cables of identical design, except one shielded and the other unshielded. An even better experiment would be to have several pairs of cables of varying designs, each pair consisting of a shielded and an unshielded version. That would be a good way to determine if "openness" were a typical characteristic of unshielded cables.

Having said that, I arrived at this (admittedly tentative) conclusion through a different route: I owned a number of unshielded cables. Other than the fact that they were all unshielded, the cables varied in design (copper/silver, stranded/solid core, single wire/multiple runs, different terminations, etc.). Because the absence of shielding was the only design feature they all seemed to have in common, I was inclined to conclude that their common characteristic of "openness" was attributable to the absence of shielding. But I recognize that this conclusion could easily be wrong.

I tend to think of "openness" as correlating with upper treble extension. For a line level interface, what would maximize upper treble extension (or at least minimize any degradation of it) would be low cable capacitance...

Al - In light of this, are there any generalizations about the typical effects of shielding on cable capacitance? Does shielding diminish capacitance?

And I should add that, while the characteristic of "openness" is partly a matter of high frequency extension, I feel like there's more to it. I don't exactly know how to describe what the "more to it" is, except to say that the sound of "openness" is also a matter of PRaT and imaging. I wish I could be more precise about it - I recognize that "openness" is a metaphor, and a rather vague one at that.

Bryon

My system hisses when I use thick speaker cables. They actually create noise.

A heretical idea - how much of the "openness" of unshielded cables could be mimicked using tone controls/EQ? An identical cable, but with shielding and a high frequency shelf boost of .5dB from around 9kHz and up. I don't know the answer and I'm just wondering.

What I'm trying to say is that I believe that useful generalizations can often be made about the typical characteristics of a particular design approach, even in the absence of carefully controlled experiments.

True, but how would you isolate the general characteristics directly due to shielding, or lack thereof? Cable type, gauge, single/stranded, connectors, solder etc. all are part of the sound of a cable. I assume (could be wrong) that shielding wouldn't be as influential to the sound as some of the aforementioned components.

I once used 47 Lab Stratos cable: 26 gauge single copper wire in plastic tubing, about as naked and unshielded as it gets. I liked it. Thinking back, I suppose it had a certain open quality to it. The 47 Lab motto of "only the simplest can accommodate the most complex" is epitomized with the Stratos cable (certainly sans shielding). But I can't help but think that the cable itself had more to do with the overall sound than it's (lack of) wrapper. Would it sound significantly more 'muffled' if it were shielded? Maybe. Actually, It would be a great cable to experiment with, going back to my first paragraph. One tiny copper wire: to shield or not to shield.

I tend to think of "openness" as correlating with upper treble extension. For a line level interface, what would maximize upper treble extension (or at least minimize any degradation of it) would be low cable capacitance (meaning low capacitance per unit length and/or minimal length), and also low output impedance of the component that drives the cable.

Just a thought to keep in mind.

Best regards,
-- Al

One would need 2 identical cables, the only difference being shielded vs non, in order to make a reasonable comparison.

Hi Tholt - This is a good point, and I agree that comparing two cables that differed only in the presence/absence of shielding would be an informative test. But I don't know that it's the only possible source of information about the typical characteristics of unshielded designs.

It seems to me that, for any category of component, whether it be cables, amps, speakers, or whatever, there are at least some generalizations to be made about the typical characteristics of a particular design approach. Hence the countless generalizations that are routinely made about SET amps, electrostatic speakers, passive preamps, or whatever. Many of those generalizations are the subject of some controversy, and nearly all of them have various exceptions, but that does not diminish the value of those generalizations as heuristics for sharing and developing communal knowledge. What I'm trying to say is that I believe that useful generalizations can often be made about the typical characteristics of a particular design approach, even in the absence of carefully controlled experiments.

Of course, I could be wrong about "openness" being a typical characteristic of unshielded cables. It would be interesting to hear from other folks who use them, to see if they have noticed something similar.

Bryon

it's a wonderful day...have three fingers of good liquor and listen to your favorite album.

Tholt: Your point is valid and in my case, I made the assumption that it was the shielding, but I could be wrong.

I had a conversation about power cords with Chris Hoff at BPT and his theory is that if you don't have any high register nasties or buzzing then shielding is a form of filtering and detrimental to the sonics. His power cord comes with or without shielding, so this would be a good cord to experiment as Tholt's "reasonable comparison" theory suggests.

Devil's advocate: Given that a system is dead quiet with unshielded cables, how are any of you comparing shielded and unshielded cables, and know that the 'openness' that was mentioned (or any other sonic difference) is due specifically to an absence of shielding? One would need 2 identical cables, the only difference being shielded vs non, in order to make a reasonable comparison.

The answer is that you would also be breaking the signal return path.

I thought so, but it was unclear to me what the audible results would be, which the rest of your answer describes very nicely. Thanks, Al.

While the hazards of using unshielded interconnects make sense to me (particularly when they are unbalanced), my experience has been that I like the sound of unshielded interconnects. I'm currently using unshielded interconnects from Morrow, but I have also used ones from Kimber and Anticables. Like other listeners, I have experienced an "openness" with unshielded designs that is appealing to me. I'm not saying you can't get that with shielded designs, but I haven't had much luck finding it, except for a $2k+ pair of Synergistic cables that I owned for a while.

I'm not suggesting that unshielded cables sound inherently better than shielded ones. Just that I've had a easier time finding the sound I was looking for with unshielded designs, at least among more affordable cables. This could, of course, be an artifact of a small sample size.

And, FWIW, I have also experienced a similar improvement in "openness" going from a heavily shielded PC to a lightly shielded PC on my preamp, as reported by Lokie.

Bryon

Here's the stupid question: ... What would happen if you "simply [broke] the chassis to chassis shield connection" in an effort to eliminate interchassis ground current?

Hi Bryon,

That isn't a stupid question. The answer is that you would also be breaking the signal return path. Keep in mind that electricity only flows if there is a complete circuit, from source to destination and back.

If you were to break that return path in the interconnect cable, and both components had 3-prong power plugs, the return path that would be taken would be through the ac safety ground wiring of the power cords, and whatever additional safety ground wiring would be necessary to reach a ground point that is common to both components. That would result in noise problems.

If either or both of the components had a 2-prong power plug, and no other ground path existed in the system between the components, then the destination component would see a "floating" input voltage (i.e., one that is not referenced to its own ground). That would result in uncontrolled behavior, and very conceivably in full-power noise levels that could damage the speakers.

Best regards,
-- Al

What do you guys mean by "dead quiet"?

Niacin - I mean (1) With the system turned on and no music playing, with the preamp volume in the maximum position I ever make use of, no noise is audible at the listening position; and (2) With the system playing music at my average listening volumes, with a good recording, during moments of silence between passages, the system sounds indistinguishable from being off.

4est and Elizabeth - You make a good point about shielding being more important in some environments than others. I've just been wondering if those environments are not as ubiquitous as manufacturers of exclusively shielded cables would lead us to believe, which brings me to...

Lokie - That Cardas video was exactly one of the examples I had in mind of a manufacturer advocating the exclusive use of shielded designs.

Al - Thanks for your excellent input. I looked at the linked paper, and I have a stupid question. Here's a passage from the paper:

To eliminate hum, we must effectively eliminate interchassis ground current. We could eliminate it by simply breaking the chassis to chassis shield connection. Of course, this alone would not solve our problem.

Here's the stupid question: Why? What would happen if you "simply [broke] the chassis to chassis shield connection" in an effort to eliminate interchassis ground current?

Thanks,
Bryon

Almarg states the reality of cable choice. Location is paramount. I do use the Speltz ICs because they keep up with all the improvements I otherwise make to my system.

A comment on the Cardas video linked to above. I don't disagree with anything that was said, but I would point out that the main reason for the dramatic changes in the waveform displayed on the oscilloscope as the cable was moved about is that the other end of the cable was not connected to anything. If it had been connected to the output of a component, the output impedance of the component, being vastly lower than the only impedance that was present in the setup (the input impedance of the scope), would have made it a completely different story.

Regards,
-- Al

I just replaced a shielded PC with a non-shielded one on my preamp and the difference was dramatically positive. I'll be trying non-shielded on the mono blocks next and hoping to hear more improvement.

Cardas has a youtube discussion on this topic stating otherwise:

http://www.youtube.com/watch?v=9uhobsHs-_o

My theory is that if you stay below a certain price point (lets just say $500) then you just have to experiment with both typologies and pick your poison. As you get over say $1000 and up you start getting the best of both worlds. Of course there's plenty of snake oil that needs to be avoided but there are some real science behind a few of the higher end cables.

Hi Bryon,

My opinion is that the case for shielding is strongest when it comes to unbalanced interconnects, both line level and phono level.

In the case of unbalanced line level interconnects, signal return currents flow in common with extraneous inter-chassis noise currents which will be present to some degree due to ground-loop effects, as explained in this paper. Since the receiving component cannot distinguish between signal and noise that may be present at its input, the voltages corresponding to those extraneous currents in the return conductor must be minimized. That means minimizing the impedance of that connection path, which in turn will be accomplished by a quality shield, but not necessarily by unshielded configurations. And certainly not by a cable configuration in which the return conductor is a simple piece of wire, which will have substantial impedance at high frequencies due to its inductance, and perhaps also higher impedance at low frequencies due to higher resistance.

As explained in the reference, an important factor in all of that is stray capacitance in the power transformer of each component. Which means that the magnitude of this effect will be system-dependent and unpredictable.

Shielding will also, as others have said, reduce noise pickup caused by rfi/emi effects, which is particularly important in the case of unbalanced interfaces due to their poor common mode noise rejection capability, and in the case of phono level interconnects due to the low signal levels that are involved.

That said, it's always been a mystery to me how, in particular, Anti-Cables unbalanced interconnects, which use a coiled piece of wire as the return conductor, apparently perform very well for many users.

All of the foregoing considerations are pretty much inapplicable to balanced interfaces, as you will realize, and so I would expect shielding to be less important for balanced interconnects.

And I would expect it to be unimportant for speaker cables, with the inter-chassis noise current consideration being inapplicable to a passive speaker, and because sensitivity to emi/rfi effects is lessened by the low impedances and relatively high signal levels that are involved. Although I do recall one thread from some time ago in which an rfi problem was resolved by changing the speaker cables.

Best regards, and happy new year!

-- Al

A lot depends on your surroundings. I used to live near a small 5 watt AM transmitter from a local religious college. Shielded interconnects, especially for phono, were required unless you wanted a lesson along with your music.

What do you guys mean by "dead quiet"? Does that mean an absence of hum?

I agree with all the above 111%. speaker, I.C., and power cables all have none to minimum shielding. I feel that it can constrict sound and dampen the dynamics of my system. Those garden hoses are also hard on the component IEC connections with their heavy weight and routing problems.

The importance of [insert any term] is sometimes exaggerated.

The above statement is so true, especially in high-end audio.

I share your experience. Both the interconnects and my speaker cables are guarded against shorts only. My system is dead quiet. Cable makers just like to spout off for personal gain.