New Posts New Posts RSS Feed - Interconnect BS vs Science
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Welcome to the Graham Slee Audio Products Owners Club

 

Open to all owners plus those contemplating the purchase of a Graham Slee audio product wishing to use our loaner program: join here
Subscribe to our newsletter here (Rules on posting can be found here)


Interconnect BS vs Science

 Post Reply Post Reply Page  123 18>
Author
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 14804
Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Topic: Interconnect BS vs Science
    Posted: 05 Mar 2022 at 5:24pm
Pre-warning: this is a rant.

There are all kinds of shields:

Medieval
Viking
Roman
Riot shields
Face shields
etc

But here I'm wanting to talk about cable shields.

Again, the word "shield" might provoke thoughts of armour provided by heavy rubber or plastics, or braids made of non-metallic or metallic materials. But mostly, these are mechanical shields.

I have even read of interconnect cables that use metallic shields which aren't used in any electrical sense - not connected. It must be that those who make them either don't understand interference, or physics, or they perhaps think that interference might add some sound-effect.

Then, there are those who think twisted pairs are effective against interference, and yes, it is true, they are, but only where the send and receive circuits are geared to interference cancellation - e.g. telephone wires - plus narrow band filtering. OK if you want a telephone sound...

But when it comes to connecting single sided inputs and outputs, a proper electrical shield is a must, but a lot of cable makers don't understand why.

This picture shows why at least 100% shielding in required.


The shield or screen (not to be mistaken by this next image)...


...holds the grounds of both send and receive equipment at the same potential. The signal is referenced to ground, and by holding the grounds at the same potential, then one doesn't electrically "wiggle" differently to the other, and the signal sees no change - and no interference.

You see, you're travelling at 67,000 mph and rotating at 1,000 mph at the same time right now, but seeing everything else within the atmosphere of planet earth is doing likewise, we don't notice, and that's how low impedance shields work.

Remove the shield (or screen - means the same thing) and replace it with a wire, as such making it the equivalent of a bell wire pair, and most of the "arrows" (inteference) lands on the signal, and also on the return wire - which was the shield, but isn't anymore - and both ends "wiggle."

But from say a CD player perhaps you don't hear any interference, and that's down to signal to noise ratios. Now phone somebody on a DECT phone and put it right up to the bell wire pair, and you'll understand signal to noise ratios.

I admit you can get some surreal sounds using bell-wire equivalent interconnects between a high level source and amp, but is surreal better or just surreal? Actually, it's just being silly, with added hubris, which causes money to change hands. I have heard the cranky responses, like "you could feel the electrons in the air listening last night". What about the music?!

A phono stage differs greatly from a CD player. A CD player output amplifier produces unity gain or perhaps a little more, but it's source - the DAC chip - is low impedance. A phono stage amplifier produces gain of around 100 with a high impedance input (MM) or gain of around 1000 for moving coil.

Capacitance and mutual inductance couple any interference introduced into the output back to the input, and where negative feedback loops are fast in high quality stages, the interference, which is at radio frequencies, gets an easy ride to the phono stage input. There being no narrow band filtering, so that you get a wide frequency response, then the interference is amplified along with the signal. The next thing you know, there is an email complaining that our phono stage has gone noisy!

Play with fire and you get burned.

But these interconnects are so well publicised. They're in a language allien to engineers, but somehow communicate great things to the average customer. The reason for this is zilch education from the glossy magazines - they, through their ignorance are also taken in. Of course they're ignorant - real measurement went out the window in the 1970's - replaced by wine tasting.

OK, there are magazines that more recently bought and boast about audio analysers, but in my opinion, it's all the gear and no idea! I've heard all the BS from some reviewers claiming how they designed semiconductors for the multi-nationals, so why are they now working for £50 a page?

I recently read about carbon fibre shielding and had to laugh in disgust. How resistive is carbon fibre? It is so resistive that they started making HT leads for petrol engines using it as the HT conductor, to reduce interference with car radios (1970s). They make resistors out of carbon - carbon is resistive - and so much so that it is useless at shielding out interference - you may as well use plastic braid!

Now, shall we go back to school and remember what the science teacher said: "there is no such thing as an insulator - just poor conductors". Then again perhaps the teacher was too interested in politics...

Shiny metals - metals that can be polished - are good conductors and make good shields: copper, steel, aluminium.

Poor conductors are wood, plastics, carbon fibres, cotton, teflon, air and a vacuum (to name a few). They will conduct electricity given sufficient potential. Air does exactly that - ever heard of lightning?

None of the above have any use in shielding.

Some think that laying or knitting a ground conductor next to a signal conductor shields the signal conductor. OK, perhaps in its shadow, but interference is from all angles. It was once explained to me over a beer, that using silver foils with one at right angles to another, afforded sufficient shielding. My expletive filled response almost got me kicked out of the bar! That was 20 years ago - the BS has been around quite some time.

What's more, is the accusation that "other" cable makers are copycats - that they're not innovative. There is a reason for people like me using properly low-impedance shielded coax - if that's what's meant by copycat. It's because it works - has always worked - and will always work.

By the way, we now have to have it made at great expense in 10km (6 mile) minimum orders. If only the BS worked, it would be much more profitable.


Edited by Graham Slee - 05 Mar 2022 at 6:12pm
Not simple enough for Google-Bot to understand...
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 14804
Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 5:57pm
A few years ago I developed a hypothesis about the best places to put tubular ferrites on interconnects. These are our Lautus cables.

Around the time of their launch I was approached by a UK distributor of a knitted interconnect for support in a court case brought about by the advertising watchdog - the ASA. I refused because I disagreed with the claims made about it. I refused because the claims made no sense in physics, and I apologetically said so.

Not long after that an anonymous university lecturer put in a complaint to the AES about my explanation of my hypothesis. I had no choice but to remove it.

I had claimed that the USB version had a ferrite placed at the anti-node of a frequency considered to be a cause of interference.

This was related to the velocity factor - which exists - but was rubbished, and so any explanation as to where the anti-nodes occur, was discounted as fantasy. At the time I had Cherry Clough assisting me with EMC (I was paying for their services), but even explaining to the ASA that I was using their own consultant used in their court case, it made no difference to the ASA. Talk about hypocrisy!

Cables have a science all of their own, but it's real science, and not the BS many are taken in by.

As such, I have decided to give away the hypothesis surrounding the Lautus USB cable for anybody to criticise. It might take me some time to gather the proof of the physics involved, but in doing so I wish to demonstrate the difference between BS cable claims and real physics.

Before closing this post, I will show you a quote from an aviation cable manufacturer, which completely rubbishes the ASA accusations:

"The delay from one end of a cable to the other is inversely proportional to the VOP: the lower the VOP %, the longer the delay.

This can be important in relative signal timing for navigation systems, for example. Delay is independent of frequency. In effect, it is the defining factor of the electrical length of a wire or cable."

The salient point being "Delay is independent of frequency".

Not simple enough for Google-Bot to understand...
Back to Top
CageyH View Drop Down
Senior Member
Senior Member
Avatar

Joined: 30 Apr 2012
Location: Toulouse, Franc
Status: Offline
Points: 1489
Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 7:05pm
On the subject of interconnects, what are your thoughts on the connectors being made out of something better than gold plated brass? Does it/can it make an audible difference if a pure copper connector is fitted?

My next question, I have seen people talk about PC-OCC and PC-CCC copper cables. Do they make a difference compared to some good quality OFC, or is the construction of the cable more beneficial than the material it has been made from?

Electrically, they probably measure the same, but can they be audibly different?
Kevin
European loan coordinator, based near Toulouse, France.
Back to Top
Ash View Drop Down
Senior Member
Senior Member
Avatar

Joined: 18 Mar 2013
Location: Dorset
Status: Offline
Points: 4127
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ash Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 7:54pm
VOP % = Velocity of Propagation, given as a percentage of the speed of light?
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 14804
Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 8:26pm
It was 1978 by the time I got around to studying digital logic, thanks to the Elektor Digibook (South Yorkshire lads weren't supposed to be educated). One thing I recall above all the truth tables and logic functions, was a thing called propagation. Even though logic chips were becoming faster (and smaller - Moore's law), if one leg of a control input had more stages than another, the result would sometimes not be as predicted. A "glitch" would occur, because one trigger would reach a gate before the other. Therefore, each leg must consist of the same number of processes, and that could take some ingenuity to comply with.

This wasn't much different to wave propagation speed which was part of my RSGB VHF licence exam cramming, which I was also trying to fit in. In the event, I didn't take the exam. You see, I was also holding down a full time job in AV.

Much later, in fact only 19 years ago, working on Nottingham University's newly acquired Boots building - installing the stage PA system in its lecture theatre, I found myself having to help the visual side of the install.

There was a 60 metre RGB cable going from a podium to a roof mounted projector, and the picture was ghosted badly. The semi-pro DVD player, even though supposed to be able to drive the cable, wasn't doing well. In my toolbox I had some clip-on ferrites, and thought it would be worth a try placing them on the cable - the ends of the cable I could reach. It didn't work, and I was about to give up, when I wondered if moving them a little way along the cable would make any difference. After a lot of mucking about, the picture sharpened and the ghosting had gone.
Not simple enough for Google-Bot to understand...
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 14804
Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 8:32pm
Originally posted by CageyH CageyH wrote:

On the subject of interconnects, what are your thoughts on the connectors being made out of something better than gold plated brass? Does it/can it make an audible difference if a pure copper connector is fitted?

My next question, I have seen people talk about PC-OCC and PC-CCC copper cables. Do they make a difference compared to some good quality OFC, or is the construction of the cable more beneficial than the material it has been made from?

Electrically, they probably measure the same, but can they be audibly different?

I'm usually told I'm wrong, so I don't like commenting on conductance issues like this. But silver is a far superior conductor than copper, and I at least, can tell the difference blindfold when a copper interconnect is replaced by a silver one. Therefore perhaps the people are right?

I don't care what purity, quality, coating or alloy they use. If it isn't shielded sufficiently and uses a "slow" dielectric, then how the hell can they tell?   
Not simple enough for Google-Bot to understand...
Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 14804
Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2022 at 8:34pm
Originally posted by Ash Ash wrote:

VOP % = Velocity of Propagation, given as a percentage of the speed of light?

I believe so. You can always check for the correct wording https://en.wikipedia.org/wiki/Velocity_factor
Not simple enough for Google-Bot to understand...
Back to Top
 Post Reply Post Reply Page  123 18>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.063 seconds.