"Eeyore" wrote in message
...


Serge Auckland wrote:

The only part of domestic equipment that would benefit from balanced
connection IS the phono cartridge, so that at least should be connected
with
XLRs. For everything else, crappy phonos is OK, if you don't have to
change
connections frequently.

That shows a STAGGERING lack of knowledge of the realities of audio and
the
environment in which it operates.

Notably with modern equipment it is totally untrue of those using
switch-mode
PSUs which invariably inject leakage currents at mains frequencies and
harmonics
into audio connections ( regardless of whether the unit is Class I -
earthed )
or Class II - double insulated ). i.e. 2 or 3 pole mains connector.

Even an unbalanced wire badly routed WILL pick up hum where the balanced
one
won't ( to the linit of the common-mode rejection ration of the
equipment ). I
came across an extraordinary example of this last year where a system
upgrade
had been installed by an idiot.

I would elaborate now but you could do worse than go to Jensen
Transformer's
site and download Bill Whitlock's paper on the use of balanced
connections.

Graham


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Maybe I have lead a sheltered life since I moved to the country.... :-) My
experience is otherwise, that decent equipment doesn't hum or pick up RF if
half-decent screened cable is used. I do accept that I've had some trouble
with SOME switched-mode powered equipment which was cured by the use of an
isolating transformer. I assumed that was an isolated example.

S.



--
http://audiopages.googlepages.com

In article ,
Serge Auckland wrote:
Maybe I have lead a sheltered life since I moved to the country.... :-)
My experience is otherwise, that decent equipment doesn't hum or pick
up RF if half-decent screened cable is used. I do accept that I've had
some trouble with SOME switched-mode powered equipment which was cured
by the use of an isolating transformer. I assumed that was an isolated
example.

Indeed. I've got a pretty big installation here with some stuff in one
part of the room - TV, PVR, satellite receiver - and the main audio stuff
at another. All interconnected unbalanced. It's also linked to sound and
vision in the kitchen so I can have the same thing playing etc while
wandering between the two. And no problems whatsoever with hum. It would
be a poor piece of design which has high levels of nasties on an audio
ground.

--
*I didn't fight my way to the top of the food chain to be a vegetarian.

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

"Dave Plowman (News)" wrote:

Serge Auckland wrote:
Maybe I have lead a sheltered life since I moved to the country.... :-)
My experience is otherwise, that decent equipment doesn't hum or pick
up RF if half-decent screened cable is used. I do accept that I've had
some trouble with SOME switched-mode powered equipment which was cured
by the use of an isolating transformer. I assumed that was an isolated
example.

Indeed. I've got a pretty big installation here with some stuff in one
part of the room - TV, PVR, satellite receiver - and the main audio stuff
at another. All interconnected unbalanced. It's also linked to sound and
vision in the kitchen so I can have the same thing playing etc while
wandering between the two. And no problems whatsoever with hum. It would
be a poor piece of design which has high levels of nasties on an audio
ground.

Try measuring one. Cable screen to mains earth either on AC voltage or low
current. It may surprise you. Mind you, if it's ALL Class II equipment the
return path to ground doesn't exist so you may get away with it.

Graham


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due to the hugely increased level of spam please make the obvious adjustment
to my email address

In article ,
Eeyore wrote:
Indeed. I've got a pretty big installation here with some stuff in one
part of the room - TV, PVR, satellite receiver - and the main audio
stuff at another. All interconnected unbalanced. It's also linked to
sound and vision in the kitchen so I can have the same thing playing
etc while wandering between the two. And no problems whatsoever with
hum. It would be a poor piece of design which has high levels of
nasties on an audio ground.

Try measuring one. Cable screen to mains earth either on AC voltage or
low current. It may surprise you. Mind you, if it's ALL Class II
equipment the return path to ground doesn't exist so you may get away
with it.

I obviously have. The only earthed component is the AV amp. Otherwise I'd
have hum ;-)

--
*There are two kinds of pedestrians... the quick and the dead.

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

Serge Auckland wrote:

Maybe I have lead a sheltered life since I moved to the country.... :-) My
experience is otherwise, that decent equipment doesn't hum or pick up RF if
half-decent screened cable is used. I do accept that I've had some trouble
with SOME switched-mode powered equipment which was cured by the use of an
isolating transformer. I assumed that was an isolated example.

On the contrary, it's increasing daily and is all the more reason to go
balanced since you don't share the screen ( and any associated earth leakage
currents ) with signal return. I've even modelled typical equipment using SMPS
supplies and a very experienced colleague of mine got a shock at how much
voltage there is on the screen of much unterminated equipment these days.
Laptops PCs are a case in note. When it's earthed to its destination it
produces a ground current in the input stage, the effect of which depends on
quality of the EMC design of the receiving equipment. Namely ALL screens should
be terminated to CHASSIS. The very reverse of how it was once done.

Graham


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