10 metres audio cable going into PC = too long?
 

On Tue, 18 Apr 2006 23:49:28 -0700, David Nebenzahl
wrote:

Don Pearce spake thus:

On Tue, 18 Apr 2006 23:32:56 -0700, David Nebenzahl
wrote:

Eiron spake thus:

David Nebenzahl wrote:

mc spake thus:

I gather that you are in the UK (hence "ring" wiring structure, which
I like, instead of the American daisychain) and that everything is
in the same room. It should work fine.

So how does house wiring work in the UK? Is there more than one
grounding ("earthing") point? And how is this better?

(Here, the Merkin practice is to ground the "service panel"--the box
where the big wires come into the house--to a single ground rod, with
everything running downstream from that.)

By the way, this brings up a strange experience I had recently doing
some wiring. I was working for a guy who owns two houses right next to
each other, and he wanted to run a cable TV connection from one house
to the other. I was about to connect the cable in the attic of the
house that was the source of the signal when I got a little tingle.
After grabbing a VOM, it turned out that there was about a 20 volt
difference between the two cable grounds.

Mc doesn't understand ground loops. You can get them between two boxes
plugged into the same double socket.

Your tingle was because your equipment is not grounded, and is perfectly
normal.

No, my tingle was because I was holding two cables strung between two
different houses, each grounded at its end. Doesn't seem normal at all
to me.

Most likely the two houses weren't on the same phase of the three
phase supply to the street. Their two grounds could have been doing
very different things voltage-wise. You should always have an
isolation transformer in a connection like this.

I seriously doubt that, because then the potential would have been more
like 120 volts, right? I think that's grasping at straws: so far as I
know, PG&E (local electricity dealer) doesn't even supply 3-phase to
residential customers. In fact, not even in come commercial districts. I
owned a small business in Berkeley (print shop) until last year, and I
remember the previous owner telling me about all the headaches he had in
having PG&E put in a 3-phase converter (in an underground vault below
the sidewalk outside). So I know that utility lines don't usually carry
3-phase power, except to large industrial customers.

Why would it be 120V? The voltage would depend on how stiff the ground
is round your way. As for three phase supply, no, individual domestic
properties generally don't get that, but streets certainly do - that
is the efficient way to deliver power.

Could be different where you are,of course.

d

--
Pearce Consulting
http://www.pearce.uk.com

10 metres audio cable going into PC = too long?
 

On Tue, 18 Apr 2006 23:49:28 -0700, David Nebenzahl
wrote:

I seriously doubt that, because then the potential would have been more
like 120 volts, right? I think that's grasping at straws: so far as I
know, PG&E (local electricity dealer) doesn't even supply 3-phase to
residential customers. In fact, not even in come commercial districts. I
owned a small business in Berkeley (print shop) until last year, and I
remember the previous owner telling me about all the headaches he had in
having PG&E put in a 3-phase converter (in an underground vault below
the sidewalk outside). So I know that utility lines don't usually carry
3-phase power, except to large industrial customers.

There'll probably be 3 phases in the street. houses, or groups of
houses will be allocated a single phase.

10 metres audio cable going into PC = too long?
 

I
I seriously doubt that, because then the potential would have been more
like 120 volts, right? I think that's grasping at straws: so far as I
know, PG&E (local electricity dealer) doesn't even supply 3-phase to
residential customers. In fact, not even in come commercial districts. I
owned a small business in Berkeley (print shop) until last year, and I
remember the previous owner telling me about all the headaches he had in
having PG&E put in a 3-phase converter (in an underground vault below
the sidewalk outside). So I know that utility lines don't usually carry
3-phase power, except to large industrial customers.



What they tend to do is supply the area with a three phase line at
around 11Kv and transform that down and then supply house number one
with phase one, house two with phase two, three with phase three, four
with phase one, five with phase two, house six with phase three and so
on. Its called load balancing between the phases...
--
Tony Sayer

10 metres audio cable going into PC = too long?
 

"David Nebenzahl" wrote ...
No, my tingle was because I was holding two cables strung between two
different houses, each grounded at its end. Doesn't seem normal at all
to me.

If they were each properly "grounded", you would NOT
have seen any voltage differential. BY DEFINITION.

(Or else the two houses were on differen planets. :-)

10 metres audio cable going into PC = too long?
 

"Laurence Payne" wrote...
There'll probably be 3 phases in the street. houses, or
groups of houses will be allocated a single phase.

Not in the parts of the USA where I have lived (up and down
the west coast). They break up the 3 phases back at the main
road and supply only one of the phases to each street (or 2-3
streets depending on the load) It is not economical to run all
3 phases along residential (or even small business) areas.

10 metres audio cable going into PC = too long?
 

"Richard Crowley" wrote in message
...
"David Nebenzahl" wrote ...
No, my tingle was because I was holding two cables strung between two
different houses, each grounded at its end. Doesn't seem normal at all to
me.

If they were each properly "grounded", you would NOT
have seen any voltage differential. BY DEFINITION.

I would almost bet that at least one of them wasn't really grounded (to the
earth).

Second choice is that high voltage is being conducted directly into the
earth from some kind of unintended connection. A bad thing.

10 metres audio cable going into PC = too long?
 

"David Nebenzahl" wrote in message
.com...
mc spake thus:

I gather that you are in the UK (hence "ring" wiring structure, which
I like, instead of the American daisychain) and that everything is
in the same room. It should work fine.

So how does house wiring work in the UK? Is there more than one grounding
("earthing") point? And how is this better?

As I understand it, the British ring system is to wire the outlets in a room
in a ring so that each of them has two parallel paths to the point where
power enters the room. As a result, a single high-resistance connection
anywhere in the ring will have almost no effect. That should do a more
reliable job of tying together all the ground connections for the different
pieces of equipment.

10 metres audio cable going into PC = too long?
 

"Eiron" wrote in message
...

Mc doesn't understand ground loops. You can get them between two boxes
plugged into the same double socket.

Two boxes with 3-wire plugs?

Could you elaborate? I thought a ground loop was due to difference in
potential of the ground connections of 2 different pieces of equipment.

10 metres audio cable going into PC = too long?
 

On Wed, 19 Apr 2006 07:26:25 -0700, "Richard Crowley"
wrote:

"Laurence Payne" wrote...
There'll probably be 3 phases in the street. houses, or
groups of houses will be allocated a single phase.

Not in the parts of the USA where I have lived (up and down
the west coast). They break up the 3 phases back at the main
road and supply only one of the phases to each street (or 2-3
streets depending on the load) It is not economical to run all
3 phases along residential (or even small business) areas.

So what do they do when somebody asks for three phase supply? Even a
reasonably small business here in the UK might well do that if their
power needs are significant. The power companies here actually prefer
to supply businesses that way, particularly if they are also careful
about their power factor correction.

Or are zoning laws in the States such that it is not possible to set
up a business in an otherwise residential area?

d

--
Pearce Consulting
http://www.pearce.uk.com

10 metres audio cable going into PC = too long?
 

On Wed, 19 Apr 2006 10:33:13 -0400, "mc"
wrote:


"David Nebenzahl" wrote in message
s.com...
mc spake thus:

I gather that you are in the UK (hence "ring" wiring structure, which
I like, instead of the American daisychain) and that everything is
in the same room. It should work fine.

So how does house wiring work in the UK? Is there more than one grounding
("earthing") point? And how is this better?

As I understand it, the British ring system is to wire the outlets in a room
in a ring so that each of them has two parallel paths to the point where
power enters the room. As a result, a single high-resistance connection
anywhere in the ring will have almost no effect. That should do a more
reliable job of tying together all the ground connections for the different
pieces of equipment.


Almost right. The ring actually goes right back to the breaker box,
which is always located where the power enters the house. But the
effect is the same.

d

--
Pearce Consulting
http://www.pearce.uk.com