UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Reply
 
Thread Tools
Old 20th Mar 2019, 1:05 pm   #501
GrimJosef
Dekatron
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 3,118
Default Re: Audiophoolery?

Quote:
Originally Posted by Radio Wrangler View Post
A surprising number of people say Faraday cage or Faraday screen whenever they are thinking of screening in general.

But as Faraday screens are special ones designed to let magnetic fields straight through, it's a bit like always prefixing the word 'Tyre' with the modifier 'Flat'.

David
It's not authoritative, I realise, but there's no mention of electric shielding in the absence of magnetic shielding here https://en.wikipedia.org/wiki/Faraday_cage.

You'll know of course that, except when they are constant, the electric and magnetic parts of the EM field are inseparable (curl E = -dB/dt, curl H = Jf + dD/dt). Anything which affects one will have at least some effect on the other. The magnitude of that effect is less at lower frequencies, but it is still there, even down in the audio range.

Cheers,

GJ
__________________
http://www.ampregen.com
GrimJosef is offline   Reply With Quote
Old 20th Mar 2019, 4:58 pm   #502
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 4,656
Default Re: Audiophoolery?

That coal bunker in post #80 looks like a "posh" version of the photo I showed in post#18.
I would love to get hold of one and test the black stuff to find out if it really is indeed coal.
Refugee is offline   Reply With Quote
Old 21st Mar 2019, 12:37 am   #503
Silvered_Mica
Pentode
 
Silvered_Mica's Avatar
 
Join Date: Aug 2003
Location: Halesowen, West Midlands, UK
Posts: 100
Default Re: Audiophoolery?

Blue arctic cable with gold connectors, they dont look as good as the toaster leads but they
cost more so they must be better
__________________
Trust Me, It's a Magic Iron (∩ ͡ ͜ʖ ͡)⊃━☆゚. * ・ 。゚, 📻📺🦔📡
Silvered_Mica is offline   Reply With Quote
Old 21st Mar 2019, 1:56 am   #504
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 3,829
Default Re: Audiophoolery?

The blue outer makes then look like arctic, but they do have silver conductors, and only 18pF/Metre capacitance! A bit of an overkill for audio methinks.
emeritus is offline   Reply With Quote
Old 21st Mar 2019, 5:08 am   #505
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 15,201
Default Re: Audiophoolery?

It looks like wikipedia reflects common usage rather than

Faraday invented his screen to demonstrate magnetic coupling between two coils was not capacitive as some others had suggested. The whole point was that it segregated electric and magnetic fields.

While Maxwell's equations show that you cannot, for alternating fields, affect one without affecting the other, it is quite possible to have a significant imbalance in the relative strengths of the two components in the near field of an object.

It is possible to make E-field and H-field probes which measure each component individually.

It is possible to generate one field disproportionately more strongly than the other, at least in the near-field.

An electromagnetic wave-pair comes winging along in free space, many lambda from its source. The two waves are in equilibrium, each inducing into the other, settled at 377 volts per metre for every ampere per metre.

It hits a Faraday shield which shunts the electric field component. On the far side of the shield, there is very little electric field wave, but the magnetic wave continues unabated. As the magnetic wave moves further beyond the shield, it induces a growing electric wave accompanying it, and that wave strts inducing back into the magnetic wave until the pair balance in equilibrium with 377 (V/m)/(A/m)

On the input side of the shield the shunted electric wave is reflected with phase reversal, and as the electric wave travels, it similarly induces a magnetic wave and they too eventually in the far field of the screen settle as an equilibrium pair

Seen in the far-field, Faraday screens don't look like screens at all. In the close field they do something useful, principally to electric field components.

A lot of the things we do are in the near field.

If you're building a sensitive receiver, then you want a proper screening box to put it in, not a Faraday screen.

If you're building a transformer, a Faraday screen between windings may be rather desirable to block capacitive coupling of rubbish on the mains, but you don't want a magnetic screen, that would ruin the transformer operation.

It is very advantageous to have separate names for general and field-specific screens.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 21st Mar 2019, 7:56 am   #506
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,452
Default Re: Audiophoolery?

"Blue arctic cable with gold connectors," I love reading the blurb these purveyors of pricey gewgaws come out with, it's like the spiel you get in posh restaurants. Who writes this twaddle? Maybe they've brought back Shelley, Keats And Joyce from the dead and have them slaving away in a cellar writing adjective laden odes to over priced bibelots.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is online now   Reply With Quote
Old 21st Mar 2019, 8:34 am   #507
Electronpusher0
Octode
 
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 1,006
Default Re: Audiophoolery?

Quote:
Originally Posted by Refugee View Post
That coal bunker in post #80 looks like a "posh" version of the photo I showed in post#18.
I would love to get hold of one and test the black stuff to find out if it really is indeed coal.
More importantly I would love to get hold of one of these "earth" boxes and test its performance.
Several versions are offered by different manufacturers but they all seem to consist of an insulated, generally wooden, box with an electrical connector, usually a binding post, to attach a wire and some form of metal strip / wire / mesh inside to make contact with the in fill.
The infill is of various materials, coal has been suggested as one.

We all love to snip and joke about these and true, the claims made as to how they work are hilarious and are not supported by any known scientific theory. They should be totally useless.

BUT has anyone actually, objectively, tested one, both electrically and by listening?

Peter
Electronpusher0 is offline   Reply With Quote
Old 21st Mar 2019, 10:45 am   #508
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 9,676
Default Re: Audiophoolery?

Quote:
BUT has anyone actually, objectively, tested one, both electrically and by listening?
For a first approximation a bag of coal with a spike in it should suffice in an ABX test and measurement.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 21st Mar 2019, 10:51 am   #509
GrimJosef
Dekatron
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 3,118
Default Re: Audiophoolery?

Quote:
Originally Posted by Radio Wrangler View Post
...

While Maxwell's equations show that you cannot, for alternating fields, affect one without affecting the other, it is quite possible to have a significant imbalance in the relative strengths of the two components in the near field of an object. ...
Yes, this is exactly right.

Quote:
Seen in the far-field, Faraday screens don't look like screens at all. In the close field they do something useful, principally to electric field components.
Even in the far-field they look like screens in the amplitude sense. As you say, there's a back-reflected wave outside the box and conservation of energy says it's taken its power from the incoming wave, leaving less to propagate beyond the screen.

Quote:
A lot of the things we do are in the near field.
When I was building these I was concerned with GHz radio waves and 10-100 nanosecond pulses and the screened rooms were quite large (~10m scale) so I wasn't always in the near-field. But the cage shown on that vibration table certainly would have been NF inside. We lined the room with copper foil but we never thought the idea of using mumetal as well, or even a cheaper high-permability material, was realistic. I don't know if anyone does. Given that the building contained a particle accelerator I know that they used non-magnetic steel to reinforce the concrete though !

Quote:
If you're building a sensitive receiver, then you want a proper screening box to put it in, not a Faraday screen.
Presumably that does have something to redirect the magnetic field too (shame there are no free monopoles to short it out ).

Cheers,

GJ
__________________
http://www.ampregen.com
GrimJosef is offline   Reply With Quote
Old 21st Mar 2019, 11:42 am   #510
mark2collection
Hexode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 368
Default Re: Audiophoolery?

All this talk of Faraday cages now makes me realise why my aunties Budgie could hit those high notes!

Not only was it grounded, it was in a way, shielded from outside interference. The sandpaper in the bottom of the cage must have acted much like one of the oak boxes, also mentioned earlier.

You'd of thought cuttlefish must have some impact on enclosure resonance.

Mark
__________________
Slowly turning the 'to-do', into 'ta-dah'
mark2collection is offline   Reply With Quote
Old 21st Mar 2019, 3:34 pm   #511
AC/HL
Moderator
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 8,866
Default Re: Audiophoolery?

Quote:
Originally Posted by Electronpusher0 View Post
BUT has anyone actually, objectively, tested one, both electrically and by listening?
And would they admit to it. Surely the whole point of the sort of apparatus discussed in this thread is that no testing is required or possible, just faith.
__________________
Bill, BVWS member
AC/HL is offline   Reply With Quote
Old 21st Mar 2019, 4:00 pm   #512
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 15,201
Default Re: Audiophoolery?

It's impossible to do that test without being affected by it and also affecting the outcome.

Anyone who has stumped up 13 grand for a badly made box of black grit and a few metal strips is not going to admit it was a waste of money.

No-one who's laid out so much brass can remain impartial. Heisenberg!

Any test done with a DIY version , however similar will just get decried by the believers as invalid because it wasn't a real one.

Take a wire outside (PME permitting!) and drive a nice copper coated steel rod into your garden, and use the whole planet!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 21st Mar 2019, 4:02 pm   #513
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 9,676
Default Re: Audiophoolery?

Even if there was a zero result "they" would say it's non conclusive "my ears are better than any other measuring device". What larks!

To (miss) quote Flanders and Swan "I never listen to music much, it's the high fidelity".

Mind you a glass (or two) of good scotch and "The Planets" sounds marvellous on my engineering based HiFi, try and measure (a good measure, two fingers is about right) that!
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 22nd Mar 2019, 1:48 pm   #514
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 4,597
Default Re: Audiophoolery?

I visit another forum that's dedicated to hifi. It wouldn't be fair to name it. Being sold on there are some second hand mains leads, varying in price from 90 to 120. I mean, the current travels through fuses that are a few thou thick, so what use are 'big' cables?!! The difference in impedance between thick cables and normal ones is the square root of sod all. And in any case, combined with the mains ring main, it all makes no difference whatsoever, and certainly not to the sound. The mind boggles at the level of snake oil being consumed.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 22nd Mar 2019, 9:32 pm   #515
Silvered_Mica
Pentode
 
Silvered_Mica's Avatar
 
Join Date: Aug 2003
Location: Halesowen, West Midlands, UK
Posts: 100
Default Re: Audiophoolery?

Surely a second hand one would be worth more as it's already been "burned in"

"Do you want to save your N.O.S. tubes from further wear?" Then you need a cable cooker.
I would love to put my scope on this thing and find out what it's really doing if anything.
__________________
Trust Me, It's a Magic Iron (∩ ͡ ͜ʖ ͡)⊃━☆゚. * ・ 。゚, 📻📺🦔📡
Silvered_Mica is offline   Reply With Quote
Old 22nd Mar 2019, 9:56 pm   #516
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,613
Default Re: Audiophoolery?

A thought just occurred to me: How is being a hi-fi bore any different from being a real ale drinker? To anybody "outside the circle", beer is just beer and music just sounds like music.

But then, a pint of real ale doesn't cost any more (sometimes less!) than a pint of cold fizzy water with flavourings and ethanol (Your bias may be showing a little here -- Ed.), and there is a difference you can taste. When it comes to expense, ticking off beers on a chart is not in the same league as spending 100 on a few metres of fancy cable .....
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline   Reply With Quote
Old 22nd Mar 2019, 10:30 pm   #517
yesnaby
Octode
 
yesnaby's Avatar
 
Join Date: Jul 2005
Location: Newport, Gwent, UK.
Posts: 1,567
Default Re: Audiophoolery?

The 'cable cooker' takes the biscuit. Careful you don't 'overcook' it though (the FAQ are hilarious).
yesnaby is offline   Reply With Quote
Old 22nd Mar 2019, 11:05 pm   #518
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 9,676
Default Re: Audiophoolery?

My cables are so old I think they are "broken in" already. As to beers, they do have different tastes (all lovely) but the evidence is gone, yum yum.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 22nd Mar 2019, 11:36 pm   #519
vidjoman
Nonode
 
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 2,527
Default Re: Audiophoolery?

My speaker cables are now about 50+ years old. perhaps that's why the music I listen to is old as well - takes all that time to travel along the cable - but sounds just as good as it did back then.
vidjoman is offline   Reply With Quote
Old 23rd Mar 2019, 12:04 am   #520
Craig Sawyers
Nonode
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 2,743
Default Re: Audiophoolery?

Quote:
Originally Posted by Silvered_Mica View Post
Blue arctic cable with gold connectors, they dont look as good as the toaster leads but they
cost more so they must be better
Interestingly, the Indian guy called Ajay Shirke that owns Siltech and Crystal Cable also owns SME and Garrard. His company is called Cadence Audio https://cadenceaudio.com/what-we-do/cadence-companies/ . I did not realise that he also owns Spendor.

Craig
Craig Sawyers is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 7:00 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.