Active Shielding for Cables - Does it Make an Audible Change

smk5r · « **on:** 8 May 2006, 02:28 am »

Before I drop some money on this, I'd really appreciate hearing peoples experiences/thoughts/recommendations on active shielding for interconnects, power cords and/or speaker cables.

Mucho gusto.

smk5r

Jon L · « **Reply #1 on:** 8 May 2006, 04:51 am »

Quote from: smk5r

Before I drop some money on this, I'd really appreciate hearing peoples experiences/thoughts/recommendations on active shielding for interconnects, power cords and/or speaker cables.

Mucho gusto.

smk5r

There's no question "active shielding" makes an audible difference, but whether YOU will like the difference will depend on your tastes, system-matching, how well it's implemented, etc.

There's no active-shield magic wand that will automatically make your sytem better to you. For example, in certain system configurations, I actually prefer the sound with active shield turned off. Then there are situations when active shield saves the day. So as always, you need to listen to it before laying down your hard-earned money...

Ethan Winer · « **Reply #2 on:** 8 May 2006, 02:22 pm »

> Before I drop some money on this <

That's definitely the correct order of events.

> I'd really appreciate hearing peoples experiences/thoughts/recommendations on active shielding for interconnects, power cords and/or speaker cables. <

In a million years I wouldn't be able to think of one thing that "active" shielding could possibly improve. If you ask these vendors for evidence they use flower prose. But if you ask them for science - what exactly is improved and by how much? - you get silence.

There are four major categories of audio parameters that define everything we hear:

* Frequency response
* Distortion
* Signal to noise ratio
* Time-based errors (wow, flutter, ringing)

I'd love to know which of these four parameters active shielding would affect.

--Ethan

John Casler · « **Reply #3 on:** 8 May 2006, 09:35 pm »

Not speaking "for or against" the topic, but simply interjecting "question/information" that I admittedly know less about than those "in the know".

I am under the impression that when electric current travels through a metal, it produces "RFI" and "EMI" (Radio Frequency Interference and ElectroMagnetic Interference) These supposedly "radiate" with various behavior and propensity depending on frequency and strength of the electrical impulse, as well as some other elements and factors.

Both of these are called "interference" because I assume they, in some way interfere with the signal carried by wiring, or they can create their own distortions from that signal.

I am under the impression, that each and every wire that is carrying current, both produces and receives these forms of interference, both from themselves and other wire carrying signal close enough to broadcast to them.

I am also under the impression that the sheilding performs the "function" of sheilding the wire from both transmitting and receiving these forms of interferences as well as developing a specific type of electrical charge themselves that has a tendency to assist in this function, or in some way ameliorate its harm.

So while I can't say that the "active" cables or their active dielectrics "DO" this, I get the impression that sheilding is supposed to do this, active or not.

I think the other concept is that if a wiring is "producing or transmitting" EMI/RFI, that certain kinds of sheilding reduce reflection of these tranmissions, or nullify them as they are "reflected back" onto the wire that produced them.

Now I cannot tell you how I got these impressions, since I haven't read of them in this much detail, however it sounds interesting

Maybe someone "who knows" can offer clarity.

CornellAlum · « **Reply #4 on:** 8 May 2006, 09:51 pm »

I have read that it is possible to actively shield any cable simply by cutting through the outer sheath and actively biasing the shield with a battery. I don't know if I believe it or not, but that's what I read on AA.

Ethan Winer · « **Reply #5 on:** 9 May 2006, 04:41 pm »

John & Cornell,

> I am under the impression that when electric current travels through a metal, it produces "RFI" and "EMI" <

Yes, there's no question that some amount of shielding is important with wires that carry low level, high impedance signals. At issue is whether a proposed new type of shielding offers any audible improvement over traditional methods. I submit that what has worked well for 100 years is all that's needed. If an alternate type of shielding really were better, the improvement could easily be measured and known. I have yet to see any evidence of this.

--Ethan

Jon L · « **Reply #6 on:** 9 May 2006, 04:55 pm »

Here's a good explanation of "active shielding," which is somewhat of a misnomer.

http://www.audioasylum.com/audio/cables/messages/4450.html

Most implementations of "active shielding" on the market today are really DBS (Dielectric Biasing System), i.e. Audioquest, Synergistic, Aural Thrills, etc. By putting a voltage bias on the shield, you are polarizing the dielectric in one direction, kind of like "breaking in" the cable really, really well all the time. It's really not like you are generating a Star-Trek force shield around the cable to block RFI/EMI...

Sonic effects are also similar to unbroken-in cable vs. well-broken in cable IME, i.e. smoother, more coherent, effortless, liquid, better imaging, etc.

markC · « **Reply #7 on:** 10 May 2006, 02:30 am »

The 4 catagories that Ethan has mentioned , IMO, have WAY more impact on your system than active shielding could. I feel that the afore mentioned areas should be persued long before active shielding. If everything in your kit is close to perfect -then go ahead.

Ethan Winer · « **Reply #8 on:** 10 May 2006, 04:34 pm »

Jon:

> Sonic effects are also similar to unbroken-in cable vs. well-broken in cable IME, i.e. smoother, more coherent, effortless, liquid, better imaging, etc. <

If that really were true, the "improvement" could easily be measured. Again, I have yet to see any evidence of that.

Mark:

> The 4 catagories that Ethan has mentioned , IMO, have WAY more impact on your system than active shielding could. <

My point is that those four categories encompass everything about audio. Not just what is important.

--Ethan

markC · « **Reply #9 on:** 10 May 2006, 09:31 pm »

Yes, Ethan. Perhaps what I should have said was that there are other factors to be concerned about first that will effect the 4 catagories to a greater degree than active shielding.

John Casler · « **Reply #10 on:** 10 May 2006, 09:47 pm »

Quote from: Ethan Winer

My point is that those four categories encompass everything about audio. Not just what is important.

--Ethan

Which one of your 4 categories tells us the SPL?

Dan Banquer · « **Reply #11 on:** 11 May 2006, 12:49 am »

O.K. I'm confused here. Can someone explain to me what active shielding and spl levels have to do with one another?

d.b.

John Casler · « **Reply #12 on:** 11 May 2006, 01:17 am »

Quote from: Dan Banquer

O.K. I'm confused here. Can someone explain to me what active shielding and spl levels have to do with one another?
d.b.

Hi Dan,

My fault, it was an "off topic" question, regarding Ethan's assertion that:

Quote

There are four major categories of audio parameters that define everything we hear:

* Frequency response
* Distortion
* Signal to noise ratio
* Time-based errors (wow, flutter, ringing)

I simply wondered which of that list included SPL, since it certainly affects "everything" we hear.

Ethan Winer · « **Reply #13 on:** 11 May 2006, 04:47 pm »

John,

> Which one of your 4 categories tells us the SPL? <

The volume control!

Wise guy...

--Ethan

John Casler · « **Reply #14 on:** 11 May 2006, 05:15 pm »

Quote from: Ethan Winer

John,

> Which one of your 4 categories tells us the SPL? <

The volume control!

Wise guy...

--Ethan

Sorry Ethan,

You know I'm simply being a "wise guy"