"Dave Plowman (News)" wrote in
message
In article ,
Arny Krueger wrote:
Agreed. If anybody doing practical audio know about
interference with signal lines, its the car audio guys.
This is the context from which I draw some of this
wisdom about the slender benefits of shielding.

Lighting circuits fed from thyristor dimmers in a TV
studio take some beating...

Meaning what?

I know that they put out wonderful collections of high harmonics of the
power line, if that is what you mean.

"Eeyore" wrote in
message
Petert wrote:

I understand that the optical connectors are known as
TOS Link - correct?

TOS Link is only really designed for short runs. The
fibre has relatively high attenuation and the bandwidth
of the transmitters and receivers is barely adequate for
the job, although it may have improved a bit in recent
years. I just checked with my studio installer friend and
he said 10m is the max using the very best quality parts.


And are there dongles available to interface between
these fibre connectors and SC/PC or LC connectors?

God knows.

For good long digital optical links you need low loss
(probably glass rather than plastic) fibre. Dunno if you
can get that with a TOS Link termination. Some heroes
actually fit better optical connectors (typically screw
thread) on their kit for exactly this reason.

The problem with quality optical is the cost of termination.

Are there advantages to be gained in using optical vice
coax?

Absence of grounding problems, but those aren't serious problems in the
digital domain, anyhow.

Is Cat5 or Cat6 used in audio?

Yes.

I will be installing
structured cabling for computing - is it worth
installing extra runs for audio etc?

Proper parts for interfacing quality audio over CAT-5 are readily available.

Do you understand balanced audio signals ?

So-called audio baluns for running audio over structured wiring exploit the
benefits of balanced audio signals.

In article , tony sayer

wrote:




OTOH - a co-axial line **inherently rejects** all such interference.


Can you explain in your own words..well perhaps tone it down a bit;, how
thats so?..

Two distinctions worth noting in this context is as follows.

1) At audio frequencies (as distinct from RF) the significant problem is
likely to be couping of signals. Not 'radiation' in the sense that - in
free space, the cable would launch power away in all directions. This means
the behaviour of cables may change when something else is near to them.

2) That the ability of something like co-ax to shield relies on symmetry
and - for radiation - the screen having a thickness somewhat greater than
the skin depth for the conductor and frequency.

Hence at low frequencies, when you have something else near a co-ax. It
isn't always certain that no signals can be coupled onto or off the co-ax.
Nearby objects can break the symmetry, and couple to any external fields.
This can be enhanced with 'sparce' braiding which has gaps in the weave of
the shield. It only acts as a cage when any object that can couple to
evenescent/leakage fields is sufficently far from the braid.

The behaviour for non-radiation coupling will also depend on the types of
fields (E/H ratio), etc. Also on grounding arrangements if not ideal since
usual coax use nominally presumes perfectly *unbalanced* operation.

Fortunately for domestic purposes, decent coax will work well enough for
people to avoid problems, despite the above.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Phil Allison" wrote in message
...


Balancing is crucial to rejecting magnetic interference,


** It has no effect at all on a mic line - you utter moron.

That's why all pro microphones are balanced I suppose?

twisting the wires is just a way of ensuring good balance by making the
two conductors as equal as possible in terms of their position within the
magnetic field and with respect to ground.


** A un-twisted pair mic line is a ** loop receiver** - it picks up
external magnetic ( ie AC hum ) fields just beautifully and feeds them to
the pre-amp input in differential mode.

Same as the wanted signal from the mic.

*My* point I think. The un-twisted pair is *not* balanced with respect to
the
magnetic field.

Co-ax does not reject magnetic interference.


** Fraid it does and very well too.

I realise this is not a very well known fact, so you had better go look it
up.

Generally, it outperforms twisted pair cable in this respect.

So explain why unbalanced connections made using co-ax cause hum loops?

Never head of "quad core" mic cable ?

Look that up too - while you are back in hell.

You mean "star quad"?, it's a time-honoured way of creating a cable that has
a better
balance than ordinary twisted pair. How does it advance your argument?


Balancing is also effective against capacitively coupled interference and
RF pick-up.


** Good shielding defeats both of them.

Balancing has no effect on RF injection or the demodulation of same.

On the contrary, since the RF pick-up is common-mode a balanced input
rejects it, assuming that the CMRR is still good at the RF frequency. If
not use a filter. Good shielding is certainly an effective way of reducing
RF pick-up, but it's not the only way and it's expensive.

Where RF is a major problem a low-pass filter between the line and the
receiving amplifier may be necessary, as it would be with a co-axial
line.

** RF energy will not enter a well shielded co-ax cable from the
utside - it just travels along the screen and should then disappear to
ground at the input socket.

RF is flowing in the screen, which is one of the signal conductors of co-ax.
So there will be some signal injection.

Same goes for a well screened mic cable.

You really don't know a single thing do you ?.

It seems as though I know a fair bit more than you do.

That's why you dish out all that crap advice you do.

The proof of the pudding is in the eating, and this particular pudding
(balanced audio on unshielded twisted pair cable) has been on the menu of
the broadcasting industry as long as that industry has existed.

David.

In article ,
Phil Allison wrote:
I do happen to work in broadcast audio.


** I suppose someone has to mop out the dunnies and clean up all the
spew and ****.

Might as well be a congenital retard like Dave.

I'm told you do that for free - with your tongue.

--
*A conscience is what hurts when all your other parts feel so good *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Phil Allison wrote:

"Dave Plowman (Nutcase)
Phil Allison

** It sure does with any unbalanced audio line - good shielding is
crucial.

It is also crucial to balanced lines, in relation to capacitively
injected noise and strong RF transmissions.

Pet, ever heard of star quad?


** Do read the whole thread - ****wit.

Only an amateur refers to it as 'quad core'


It is the best balanced cable for
interference rejection and is pretty universal for pro mic circuits.

** ********.

I forgot you lived in a third world country. Never mind - it can be
imported. Just save up your social security checks. And try it.


And has a rudimentary lapped screen

** ********.

Keep on making a fool of yourself.


** Nonsense.

Fact is, balancing has NO effect on magnetic field interference to a
line - it is only the TWISTING of the signal carrying pair has any
benefit in this regard.

That's not totally so either.


** Go read why " star quad " is better - ****WIT.

It is all to do with the additional twisting !!!

Then why not just twist a pair a bit tighter?



...... Phil

See it's taking you longer and longer to remember your name.

--
*Can atheists get insurance for acts of God? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Arny Krueger wrote:
"Dave Plowman (News)" wrote in
message
In article ,
Arny Krueger wrote:
Agreed. If anybody doing practical audio know about
interference with signal lines, its the car audio guys.
This is the context from which I draw some of this
wisdom about the slender benefits of shielding.

Lighting circuits fed from thyristor dimmers in a TV
studio take some beating...

Meaning what?

Interference. Far worse than in the average car.

I know that they put out wonderful collections of high harmonics of the
power line, if that is what you mean.

They were a real problem in practice.

--
*How many roads must a man travel down before he admits he is lost? *

Dave Plowman London SW
To e-mail, change noise into sound.

"David Tosser
"Phil Allison"

Balancing is crucial to rejecting magnetic interference,

** It has no effect at all on a mic line - you utter moron.

That's why all pro microphones are balanced I suppose?


** It is way all balanced lines use *twisted* signal conductors - ****wit.

Cos balancing alone does not reject magnet field interference.


twisting the wires is just a way of ensuring good balance by making the
two conductors as equal as possible in terms of their position within
the
magnetic field and with respect to ground.


** A un-twisted pair mic line is a ** loop receiver** - it picks up
external magnetic ( ie AC hum ) fields just beautifully and feeds them to
the pre-amp input in differential mode.

Same as the wanted signal from the mic.

*My* point I think. The un-twisted pair is *not* balanced with respect to
the magnetic field.

** Complete drivel.

Twisting the signal conductors and balancing are quite separate matters.


Co-ax does not reject magnetic interference.


** Fraid it does and very well too.

I realise this is not a very well known fact, so you had better go look
it
up.

Generally, it outperforms twisted pair cable in this respect.

So explain why unbalanced connections made using co-ax cause hum loops?


** So you have no idea these are separate phenomena ?



Never head of "quad core" mic cable ?

Look that up too - while you are back in hell.

You mean "star quad"?, it's a time-honoured way of creating a cable that
has a better balance than ordinary twisted pair.

** The twisting is more elaborate to reduce loop area and magnetic field
injection.

Would still be effective even if the cable was used unbalanced.



Balancing is also effective against capacitively coupled interference
and
RF pick-up.


** Good shielding defeats both of them.

Balancing has no effect on RF injection or the demodulation of same.

On the contrary,


** God you are a utter, know nothing ****wit.


since the RF pick-up is common-mode a balanced input
rejects it, assuming that the CMRR is still good at the RF frequency.

** False assumption.

CMRR falls off at high audio frequencies and is gone at RF .


Good shielding is certainly an effective way of reducing
RF pick-up, but it's not the only way and it's expensive.


** Nonsense - its comes free with all co-axial and mic cable.

Only penny pinching TOTAL ****IWTS try to use cat 5 for domestic audio.


Where RF is a major problem a low-pass filter between the line and the
receiving amplifier may be necessary, as it would be with a co-axial
line.

** RF energy will not enter a well shielded co-ax cable from the
outside - it just travels along the screen and should then disappear to
ground at the input socket.

Same goes for a well screened mic cable.

You really don't know a single thing do you ?.

It seems as though I know a fair bit more than you do.


** Shame that is only in your demented, autistic imagination.

Cos every single thing you have said is WRONG.


That's why you dish out all that crap advice you do.

The proof of the pudding is in the eating, and this particular pudding
(balanced audio on unshielded twisted pair cable) has been on the menu of
the broadcasting industry as long as that industry has existed.


** Got nothing to do with attempting use unshielded cat 5 for audio strung
around a house.




...... Phil

"Dave Plowman (Nutcase)
Phil Allison

** It sure does with any unbalanced audio line - good shielding is
crucial.

It is also crucial to balanced lines, in relation to capacitively
injected noise and strong RF transmissions.

Pet, ever heard of star quad?


** Do read the whole thread - ****wit.


It is the best balanced cable for
interference rejection and is pretty universal for pro mic circuits.

** ********.

I forgot you lived in a third world country.

** You are nothing but ****ing LIAR.



And has a rudimentary lapped screen

** ********.

Keep on making a fool of yourself.

** You are nothing but a ****ing LIAR.



** Nonsense.

Fact is, balancing has NO effect on magnetic field interference to a
line - it is only the TWISTING of the signal carrying pair has any
benefit in this regard.

That's not totally so either.


** Go read why " star quad " is better - ****WIT.

It is all to do with the additional twisting !!!

Then why not just twist a pair a bit tighter?


** Go look it up

- you dumb as dog **** ARSEHOLE !!!!




...... Phil

"Arny Krueger"

Are there advantages to be gained in using optical vice
coax?

Absence of grounding problems,

** The OP thinks optical = analogue.

You must learn to read all of a thread for CONTEXT before butting in.


Proper parts for interfacing quality audio over CAT-5 are readily
available.


** Are they ? Bet they are not cheap.

Hardly economic for short runs around a house.

Silly to risk RF and impulse noise injection when shielded cable is readily
available.

Even shielded cat 5.



So-called audio baluns for running audio over structured wiring exploit
the benefits of balanced audio signals.


** Arny always loves to ALLUDE to his store of secret knowledge.

It allows him to PONTIFICATE endlessly and nauseatingly.

But if you ever get to see his " store " - you'll find the cupboard is
bare.




....... Phil