Cables

Hi,

> My thought is why don't we make cable shields from magnetic
> metals?!

Various practicalities? I for one would not fancy installing cables shielded with 3mm Mu-Metal (a nickel/iron alloy which in the stated thickness will give maybe 60-70db attenuation of a 50Hz magnetic field....).

Ciao T

 

I'd agree with 3DSONICS in everything he has said....
I've been building cables for the best part of 25 years and can hear many differences but not swapping a symetrical cable round. Even psudoblanced cable are hard to differenciate the when swapped. I don't bother with shielding on my cable but rely on either tight twisting or seperation. Normally if your getting EMI/RFI you've problems else where that need sorting first.

Oh and as 3D states can you make your statments less confrontational its starting to grate on my nerves. You'll probabley get more replies too.

 

Ferrite?

Hi.

Anyone who has anything to say in the subject of Ferrites on Cables? What is the effect and how to apply them.

Anders

 

Hi,

Yes.

They stop the cable from being an efficienient aerial for EM Waves with wavelength corresponding to integer multiples and fractions of the cables length, assuming they have been suitably selected.

Commonly they are available as "clip on" items for computer cables to reduce radiated EMI.

Another trick one may use is to add a "shorted turn" or two around the ferrite core (using copper foil). This turns the ferrite core into a transformer at high frequencies which will result in any fields traveling in the cable above certain frequencies to be induced in the "shorted turn" secondary, which will efficiently convert the magnetic HF energy into heat.

Due to the large number of variables involved the effects of ferrites on cables and sound are hard to predict and range from zero to profound. Often moving a ferrite along the length of the cable can work to "tune" the rejection of RF by placing the ferrite in a "peak" node of the waveform.

I usually suggest to keep a box full of them and to be empirical. Be prepared also to find that ferrites make things worth and in such cases remove them.

In closing, contrary to the normal "dumbed down" view of how interconnections in cases of mains powered, interconnected equipment (audio or not), the subject is very complex, mainly due to the use of unbalanced interfaces (both interconnects and speakers but also mains) and conflicts between electrical safety compliance, EMC directive compliance, Power Line distortion compliance and requirements for undisturbed signal transmission (similar problems exist in other branches of electronics concerned with measuring accuratly things for process control and other purposes).

Using transformercoupled, floating balanced interconnections such as are still standard in studio's would do much to reduce the problem complexity and to reduce the potential for cable related sonic changes.

A good read in the context is Bill Whitlock - Subtleties count in wide dynamic range analog interfaces - EDN 1998 Issue 12 June 4th.

Another good read is by my buddy Pete, (thinly) disguised as "review" of a cable it is actually an excellent primer on the basics and concepts, for a really freaky view of the subject I suggest anything on noise in audio gear by the late John "Buddah" Camille, mainly in Valve/Cybervalve and some crculating papers in the UltraFi Underground (sorry, no links, I might have a copy somewhere I can post in my technical discussion group on yahoo).

Ciao T

 

Hi.

Thanks T for your reply. Found an interesting article on ferrites that seems accurate to me, http://www.ce-mag.com/archive/02/11/may.html . My conclusions of this cable debate are these. 1. To reduce magnetically induced hum the best solution is to have the signal and ground wires in either a hard twist or maybe even better a tight 4-strander braid. 2. To reduce electrostatic (capacitive) coupling are ferrites probably a better solution than shielding if the source and load impedance is low while shielding probably works better then ferrites if the source and load impedance is high. This subject is definitely not my backyard so I hope I have got it right. If I have understood this subject right shielding should have a much better effect in my Guitar cable where the pickups have an impedance of 7 kOhm and the amplifiers input has 1 MOhm impedance then in my interconnects. When it comes to power cable, loudspeaker cables and interconnects it seems to be worth a try with a hard braid and ferrites. Plesae correct me if I'm wrong.

Anders

 

How do you know that you can "tune" the rejection of RF by placing the ferrite in a "peak" node of the waveform ?


The wavelength would be too small to be affected by any changes in position of the ferrite.

you meant antinode didnt you ?

 

Hi,

Yup, completely right. Also, your guitar pickup has astrong inductive component, which will increase the impedance towards higher frequencies and strongly so.

So, in a 5m guitar cable or even a very long microphone cable electrostatic screens make a lot of sense, but in a 1m Interconnect between a modern CD-Player and and amplifier it makes little sense.

I would suggest to leave screens off in most cases, it reduces the capacitance and does not interfere with the signal field in the actual conductor.... If you need a screen use one but ideally only then.

Ciao T

 

Hi,

Basic RF theory.

Are you SURE?

A 144MHz wave (2m Ham Radio Band) has a wavelength of 2m. So placing a ferrite on a 2m Mains Cable (for example) will have no significant effect if the ferrite is placed at 1m length (antinode) but (assuming the ferrite is effective in the range) it will if placed at 25cm and 75cm (nodes or as I colloquially use - peak - node, in other words a point at the length of a monople aerial where current is at maximum.

Nope, Node, in that parlance. Placing a ferrite in the antinode will do very little, no currentflow.

As I usually suggest little experiments, take a portable FM radio and a ferrite sleeve effective to > 100MHz. Extend the aerial fully and slide the ferritre along the length of the aerial, you will noytice several points where the reception is strongly disrupted and others where it is not....

A long conductor does not stop being an aerial just because we call it a speaker cable or an interconnect or the like, the conductor actually does not know what we call it, it merely obeys the physical laws that apply to this continuum and plane.

Please consider to word your statements less controversially, your wording grates and tends to push me towards giving a sarcastic and snappy reply you may not appreciate.

We have a saying in germany, the way you shout into the woods that is how the echo comes back.

Ciao T

 

Well... I might just get some ferrites to put on my mains cables now!

I know I asked this before but.. what sort of negative effects can a screen have in an audio interconnect? You say they are not much help and have explained why, but I have not seen much reason NOT to use one if the user has the choice of either.

Basically I'm wondering if I should swap out my triple screened cable between pre and power amps for a non-screened tightly twisted balanced connection. My current connection is single-ended but I don't hear much difference between screened balanced and screened single-ended so any difference would have to come from the removal of the screen, twisting and perhaps addition of ferrite?

I considered going 22K gold solid-core but it does work out too much for two 4m runs when its balanced. A 1m interconnect isnt too much though. Anybody have experience of solid gold interconnects? How do they sound different to solid silver?

 

how did you work that out ?

Please show me.

We've already said sorry and made up, so now we are both free to express our opinions freely.

I will not take any offense to your snappy responses.

 

the term node is used widelt to describe the minimum point of current, so that is why I said antinode.

 

Johnny, just out of interest are you foreign? It’s just something about your grammatical structure that makes me think you might be?

 

Hi,

That is where I use them, on ALL mains cables.

Again, this heavily depends on conditions. Easy ones are related to piezo and triboelectrical effects in the insulation, increased capacitance and possible signal dependent (acoustic coupling) capacitance, then we have eddy current signal loss (which may be linear, nonlinear with frequency or otherwise nonlinear).

Note that I am not either pro- or anti- screens or indeed with any specific cable feature. Any possible design has uses and occasions where there is no benefit and occasions where disbenefits accrue.

I particular took exception to Johnny's claim that the presence or absence of a screen determine the quality and usefullness as interconnect or not. It doesnt.

The answer is: "Be empirical". In this day and age empiricism is widely sneered at and usually people in so-called scientific circles reject empiricism and demand first acomprehensive theory and the experimental proof and dislike empirical data that runs counter to their pet theories.

So, make two cables identical in all particulars but one set screened and the other not and have a listen, preferably blind, but as you do a bit of recording you can probably trust your hearing reasonably well in situations where there you have no stake or interest (except for finding out which is better for your use) and hence have no strong expactation of the outcome (which acts as randomising factor in blind testing and prejudices sighted tests unduly).

Ciao T

 

but the ferrite only works for certain frequencies so how will that help with shielding ?

 

Ferrite / coil ?

Hi.

What happens with bass response if put a couple of ferrite rings on my loudspeaker cable and turn the cable two rounds in each ring? Will they become coils that makes me loose bass or is this effect neglectable?

Anders

 

No No your not free to revert to snappy responces [read arogent for snappy]. I don't know which forums you have used but on this one we like to be treated with a little respect. A previously pointed out you will get a lot more from the forum if your pleasent. Why do you need to be confrontational...

I have to say the your on the point of making click the ignore box, if enough people do that your going to be left hi and dry.

 

Hi,

Typhically ferrites will have a maximum impedance at a given frequency, below that the impedance falls the same as any inductor and above that it becomes prorgessively less effective. All this can be obtained from the manufatcurers datasheets.

Also, PLEASE NOTE that I am not recommending "ferrites as screening". In fact I do not recommend anything at all to anyone, except to try things out for themselves. If RFI is encountered it is recommended to try ferrites, on screened or unscreened cables.

Past that I merely point out that traditional electrostatic screens are largely ineffective at screening out any electromagnetically coupled disturbances untill the wavelength becomes very short and that any electrostatically coupled disturbances in modern systems are very low in level, at least in the audio range.

So nothing has changed and I must say I find your style of debating in a public forum EXTREMELY deplorable. I tend to agree with Zanash, your approach grates with the general sensibilities I am used to here in the UK and in Europe.

You appear arrogant to a degree much more than I usually do, rude and unpleasant, due to the writing style you evidence. This may not be your intention, PLEASE try changing that.

Ciao T

 

Hi,

You will create a bit more of inductance, not all that much.

The effect in the audio range is negligable (a german company, HMS, has their horrendously expensive top of the range speaker cable completely clad into ferrites, end to end and still measures rulerflat in the audio range). Past that, "coils" do not make you "loose bass", they actually suppress high frequencies, dependent on their value (as said, ferrites usually do nothing anywhere near the audio range).

I will also repeat, the "clip on" ferrites which are available for Computers are very inexpensive and added/removed in seconds. So PLEASE be empirical and try it. That will tell and teach you more about what is going down than twenty pages of discussion.

Ciao T

 

(as said, ferrites usually do nothing anywhere near the audio range).

It depends on what you define as the audio range thorsten.
In any case, are you able to substantiate your claim ? or more importantly, are you going to ?

Why do you say that b&w speakers are distorted and sound awful. I have heard other amateurs make derogatory remarks about b&w, but please consider the amount of r&d that goes into the designs. Amateur hobbyists simply do not have the tools and equipment at their disposal, to create curved shapes etc. or the same level of research and development.

I had a discussion with Mr Dickie about loudspeaker design and there is no doubt in my mind that he is a world class designer. He desgned the flagship nautilus model . Have you even read the design papers on the nautilus ?

I must hasten to add that arrogance is something one acquires over many years, through experience.

 

Hi,

First, I define the traditional audio range the same way as anyone else, that is 20Hz-20kHz. I also allow for an extended range that reaches out to 50kHz where audible difference may be observed, though no perception of steady state tones is possible.

Yes, the added inductance (by adding a clip on ferrite) is small enough to make no observable difference in the traditional and extended audio range. We are usually in the nH at best single number uH range, negigable compared to the inductance present in the speaker cable.

I do not say that at all. I merely observe that B&W Speakers have very high distortion levels (well above average for HiFi Speakers) and high levels of thermal compression (again compared to average).

I do not say they sound awful. In the absolute sense they do not sound as all, as "sound" implies the presence of an observer whose perception will interact.

In a more or less absolute sense we can observe that the more or less objective performance of many B&W speakers is of a certain nature. I do so.

It seems to have done little to improve the objective performance of the speakers produced. Bose too place large amounts of money into R&D and more into marketing.

I fail to see the relevance. Is anything inherently better because it has a curved shape? Is anything inherently better because the company does a lot of R&D?

Or is it inherently better because it observably performs better?

He may very well be. That does not change the way in which many of the companies products perform.

As it so happens, yes. And?

May I ask if you read any of the notes on Audio and Speakers which I have written?

May I ask if you actually have looked at the measured performance B&W Speakers, especially in respect to distortion and compression?

Anyway, what has B&W to do with a discussion of cables?

Ciao T

PS, watching "The prince of Darkness", nicely creepy