ground-loop problems

[Dave Plowman (News)]

In article <%MsYl.18766$jZ1.14026@flpi144.ffdc.sbc.com>,
David <someone@somewhere.com> wrote:

If there are indeed three phases, would not the phase to
phase voltage be 220v times sqrt(3) = 381v?

Voltage in the UK is still 240v - although the tolerance has been altered
to bring it into line with Europe so is quoted as 230v.

3 phase distribution boards are normally marked 'danger 415v'

Dunno where I got the 440 from. ;-)

--
*Warning: Dates in Calendar are closer than they appear.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[isw]

In article <506a53c000dave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <%MsYl.18766$jZ1.14026@flpi144.ffdc.sbc.com>,
David <someone@somewhere.com> wrote:
If there are indeed three phases, would not the phase to
phase voltage be 220v times sqrt(3) = 381v?


Voltage in the UK is still 240v - although the tolerance has been altered
to bring it into line with Europe so is quoted as 230v.

3 phase distribution boards are normally marked 'danger 415v'

Dunno where I got the 440 from. ;-)

In the US, whether it's 440V or 480V depends on whether the three-phase
transformer is "delta" or "wye" connected. Same for 220/240 and 110/120.

Isaac

 

[Dave Plowman (News)]

In article <slrnh3dpn2.lnb.aznomad.3@ip70-176-155-130.ph.ph.cox.net>,
AZ Nomad <aznomad.3@PremoveOBthisOX.COM> wrote:

Fault condition - you could have 220v between two surfaces. And silly
because there's no need.

No you wouldn't. You'd have 0 V between two chassis connected to the
ground. Having one device with it's ground connected to the hot is
rare. Having two such devices plugged in different outlets
yet within arm's grasp of each other is fantasy.

Sadly such things can happen. Rare maybe, but why take the risk when it's
avoidable?

--
*It was recently discovered that research causes cancer in rats*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <h16o91$rs6$1@reader1.panix.com>,
David Lesher <wb8foz@panix.com> wrote:

Why would you want 'three or four' 20 amp circuits in a 'family' room?

Why would anyone drive down the wrong side of the road, or use Whitworth
threads? It's not usual for a large room to have multiple circuits. If we
had a 7500 watt scheme, one would do, I suspect.

Is there a limit to the number of outlets on one circuit?

--
*Why do the two "sanction"s (noun and verb) mean opposites?*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[AZ Nomad]

On Tue, 16 Jun 2009 10:23:31 +0100, Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <slrnh3dpn2.lnb.aznomad.3@ip70-176-155-130.ph.ph.cox.net>,
AZ Nomad <aznomad.3@PremoveOBthisOX.COM> wrote:
Fault condition - you could have 220v between two surfaces. And silly
because there's no need.

No you wouldn't. You'd have 0 V between two chassis connected to the
ground. Having one device with it's ground connected to the hot is
rare. Having two such devices plugged in different outlets
yet within arm's grasp of each other is fantasy.

Sadly such things can happen.
Name one single case.

Rare maybe, but why take the risk when it's
avoidable?
Why run power into your house at all if you are unwilling even to risk

wiring problems that border on fantasy?

 

[Dave Plowman (News)]

In article <slrnh3f9vi.jp5.aznomad.3@ip70-176-155-130.ph.ph.cox.net>,
AZ Nomad <aznomad.3@PremoveOBthisOX.COM> wrote:

On Tue, 16 Jun 2009 10:23:31 +0100, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnh3dpn2.lnb.aznomad.3@ip70-176-155-130.ph.ph.cox.net>,
AZ Nomad <aznomad.3@PremoveOBthisOX.COM> wrote:
Fault condition - you could have 220v between two surfaces. And silly
because there's no need.

No you wouldn't. You'd have 0 V between two chassis connected to the
ground. Having one device with it's ground connected to the hot is
rare. Having two such devices plugged in different outlets
yet within arm's grasp of each other is fantasy.

Sadly such things can happen.

Name one single case.

How would I be able to if it happened in the US?

Rare maybe, but why take the risk when it's
avoidable?

Why run power into your house at all if you are unwilling even to risk
wiring problems that border on fantasy?

Thought you still have some two pin appliances - so no safety earth and
the plug can be reversed. Are you really saying you can't imagine a
scenario where two faults resulted in the possibility of touching two
phases? Of course if everything is protected by RCBOs etc it wouldn't much
matter. But I got the impression some older installations weren't.

--
*I like cats, too. Let's exchange recipes.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[David Lesher]

"Dave Plowman (News)" <dave@davenoise.co.uk> writes:

Why would you want 'three or four' 20 amp circuits in a 'family' room?

Why would anyone drive down the wrong side of the road, or use Whitworth
threads? It's not usual for a large room to have multiple circuits. If we
had a 7500 watt scheme, one would do, I suspect.

Is there a limit to the number of outlets on one circuit?

I don't know, but likely. Many building codes require outlets every
'n' feet, not crossing a doorway. A friend had a vestibule between the
house and garage:

<---7 ft -->
--=====-----
| |
x x
| |
--x--------

where x are doors, and === is a sliding door. To meet the
code, he had 5 outlets in the space. There's no furniture
but lots of places to plug in anything....


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[Michael A. Terrell]

David Nebenzahl wrote:

On 6/15/2009 12:13 PM Michael A. Terrell spake thus:

The US philosophy is to only trip breaker in a fault condition and
that means extra capacity.

So what is the UK philosophy in this regard?

Who knows? One Brit makes one claim, and another calls him a liar.


--
You can't have a sense of humor, if you have no sense!

 

[Eeyore]

William Sommerwerck wrote:

I'd like to thank everyone who took the time to respond to my question. I
was particularly appreciative of those that told me about noise & grounding
problems I've never even heard of.

I'm not quite ready to put everything on one circuit. So I'm going to call
both Parasound and Pioneer to see what insights, if any, they have to offer.

Again, thank you-all for your help.

PS: As for balanced cables being an OTT solution for home installations... I
have five power amps, four of which sit next to the speakers they drive.
Given the distances, and the fact that the amps draw significant current,
and some are on different circuits, it would not be a good idea to use
unbalanced cables.

I could tell you a thing or two about that as well. Balanced connections are
VERY advisable especially with the rise in use of SMPSs with their associated
ground leakage currents and the general increase in EMI pollution in the aether.

Graham


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

 

[William Sommerwerck]

"Eeyore" <rabbitsfriendsandrelations@notcoldmail.com> wrote in message
news:4A4B2EB0.9D9F3AD5@notcoldmail.com...

William Sommerwerck wrote:

I'd like to thank everyone who took the time to respond to my question. I
was particularly appreciative of those that told me about noise &
grounding
problems I've never even heard of.
I'm not quite ready to put everything on one circuit. So I'm going to
call
both Parasound and Pioneer to see what insights, if any, they have to
offer.
Again, thank you-all for your help.
PS: As for balanced cables being an OTT solution for home
installations...
I have five power amps, four of which sit next to the speakers they
drive.
Given the distances, and the fact that the amps draw significant current,
and some are on different circuits, it would not be a good idea to use
unbalanced cables.

I could tell you a thing or two about that as well. Balanced connections
are VERY advisable especially with the rise in use of SMPSs with their
associated ground leakage currents and the general increase in EMI
pollution in the aether.

I've done some research, and have been unable to find anything "definitive"
about "grounding and its discontents".

I did ask the sous-manager of the Bellevue Magnolia, and was told that
Magnolia did not require balanced cabling in home-theater systems -- it was
the customer's choice. He didn't say how often they had problems with ground
loops, buzzing, etc. The implication was that such problems were
sufficiently rare that there was no need for Magnolia to insist on balanced
lines.

I found the explanations given in this group about how unbalanced lines were
inherently okay, and there was no reason one should ever have problems with
ground loops, to be incomprehensible. (To me, anyway.)

I don't believe explanations until I actually understand them. For example,
it took me 50 years (yes!!!) to understand why inductor saturation causes a
loss of inductance. I'd never seen an explanation that went beyond "It is
intuitively obvious, of course..."

Ditto for ground loops. I finally figured it out a few years ago. Briefly...
Voltages are potential /differences/, not absolutes. When you connect an
unbalanced output to an unbalanced input, the latter "sees" the voltage
difference between the output line and ground of the "sending" device. If
the AC grounds of the two devices are not at the same potential, the input
will see this difference superimposed on the signal -- et viola! -- hum.

"It stands to reason" that, even if two devices are on the same power line,
the farther apart they are, and the greater the difference in the current
they draw, the greater the likelihood there will be a significant difference
in the AC potentials of their chassis.

----------

I cannot find a cable isolation transformer suitable for digital-delivery
systems. (Parts Express sells one, but says it isn't suitable for digital,
which at least one buyer confirmed.) I put one together from two baluns, but
haven't tested it yet.

Oddly, Comcast has not such device, free or even for sale. They say that
customers either don't have problems, or don't complain about them.

 

[AZ Nomad]

On Wed, 1 Jul 2009 07:10:31 -0700, William Sommerwerck <grizzledgeezer@comcast.net> wrote:

I cannot find a cable isolation transformer suitable for digital-delivery
systems. (Parts Express sells one, but says it isn't suitable for digital,
which at least one buyer confirmed.) I put one together from two baluns, but
haven't tested it yet.

Oddly, Comcast has not such device, free or even for sale. They say that
customers either don't have problems, or don't complain about them.

Use an optical cable.

 

[William Sommerwerck]

"AZ Nomad" <aznomad.3@PremoveOBthisOX.COM> wrote in message
news:slrnh4msku.sl9.aznomad.3@ip70-176-155-130.ph.ph.cox.net...

On Wed, 1 Jul 2009 07:10:31 -0700, William Sommerwerck
grizzledgeezer@comcast.net> wrote:

I cannot find a cable isolation transformer suitable for digital-delivery
systems. (Parts Express sells one, but says it isn't suitable for
digital,
which at least one buyer confirmed.) I put one together from two baluns,
but haven't tested it yet.

Oddly, Comcast has not such device, free or even for sale. It says
customers either don't have problems, or don't complain about them.

Use an optical cable.

Oh? How? The system uses coax.

Does someone make an RF/optical, optical/RF converter?

 

[AZ Nomad]

On Wed, 1 Jul 2009 07:50:11 -0700, William Sommerwerck <grizzledgeezer@comcast.net> wrote:

"AZ Nomad" <aznomad.3@PremoveOBthisOX.COM> wrote in message
news:slrnh4msku.sl9.aznomad.3@ip70-176-155-130.ph.ph.cox.net...
On Wed, 1 Jul 2009 07:10:31 -0700, William Sommerwerck
grizzledgeezer@comcast.net> wrote:

I cannot find a cable isolation transformer suitable for digital-delivery
systems. (Parts Express sells one, but says it isn't suitable for
digital,
which at least one buyer confirmed.) I put one together from two baluns,
but haven't tested it yet.

Oddly, Comcast has not such device, free or even for sale. It says
customers either don't have problems, or don't complain about them.

Use an optical cable.

Oh? How? The system uses coax.

Does someone make an RF/optical, optical/RF converter?

Yes. google is your friend.

 

[Dave Plowman (News)]

In article <h2fqvg$vjf$1@news.eternal-september.org>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

"Eeyore" <rabbitsfriendsandrelations@notcoldmail.com> wrote in message
news:4A4B2EB0.9D9F3AD5@notcoldmail.com...
William Sommerwerck wrote:

I'd like to thank everyone who took the time to respond to my
question. I was particularly appreciative of those that told me about
noise &
grounding
problems I've never even heard of. I'm not quite ready to put
everything on one circuit. So I'm going to
call
both Parasound and Pioneer to see what insights, if any, they have to
offer.
Again, thank you-all for your help. PS: As for balanced cables being
an OTT solution for home
installations...
I have five power amps, four of which sit next to the speakers they
drive.
Given the distances, and the fact that the amps draw significant
current, and some are on different circuits, it would not be a good
idea to use unbalanced cables.

I could tell you a thing or two about that as well. Balanced
connections are VERY advisable especially with the rise in use of
SMPSs with their associated ground leakage currents and the general
increase in EMI pollution in the aether.

I've done some research, and have been unable to find anything
"definitive" about "grounding and its discontents".

I did ask the sous-manager of the Bellevue Magnolia, and was told that
Magnolia did not require balanced cabling in home-theater systems -- it
was the customer's choice. He didn't say how often they had problems
with ground loops, buzzing, etc. The implication was that such problems
were sufficiently rare that there was no need for Magnolia to insist on
balanced lines.

Err, either they're fitted with balanced connectors or they're not. To
modify an unbalanced unit isn't a trivial matter. Involves either using
expensive transformers at either end of the line or incorporating new
electronics. You don't just buy a new cable. ;-)

I found the explanations given in this group about how unbalanced lines
were inherently okay, and there was no reason one should ever have
problems with ground loops, to be incomprehensible. (To me, anyway.)

It's really quite simple. With unbalanced you mustn't have a second
connection to ground *anywhere*. Which means only one of the bits of
equipment must have the mains ground connected - since with most the mains
ground will be connected to the signal ground. Also applies to video and
aerial connections.

I don't believe explanations until I actually understand them. For
example, it took me 50 years (yes!!!) to understand why inductor
saturation causes a loss of inductance. I'd never seen an explanation
that went beyond "It is intuitively obvious, of course..."

Ditto for ground loops. I finally figured it out a few years ago.
Briefly... Voltages are potential /differences/, not absolutes. When you
connect an unbalanced output to an unbalanced input, the latter "sees"
the voltage difference between the output line and ground of the
"sending" device. If the AC grounds of the two devices are not at the
same potential, the input will see this difference superimposed on the
signal -- et viola! -- hum.

"It stands to reason" that, even if two devices are on the same power
line, the farther apart they are, and the greater the difference in the
current they draw, the greater the likelihood there will be a
significant difference in the AC potentials of their chassis.

----------

I cannot find a cable isolation transformer suitable for
digital-delivery systems. (Parts Express sells one, but says it isn't
suitable for digital, which at least one buyer confirmed.) I put one
together from two baluns, but haven't tested it yet.

Oddly, Comcast has not such device, free or even for sale. They say that
customers either don't have problems, or don't complain about them.

In the UK pretty well all audio etc equipment sold is class II insulated
so doesn't need a safety ground. But may have one for other reasons.
Lift all of them apart from the one on the AV amp. You'll not then have a
ground loop problem.

--
*If you don't pay your exorcist you get repossessed.*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[William Sommerwerck]

I did ask the sous-manager of the Bellevue Magnolia, and was told that
Magnolia did not require balanced cabling in home-theater systems -- it
was the customer's choice. He didn't say how often they had problems
with ground loops, buzzing, etc. The implication was that such problems
were sufficiently rare that there was no need for Magnolia to insist on
balanced lines.

Er, either they're fitted with balanced connectors or they're not. To
modify an unbalanced unit isn't a trivial matter. Involves either using
expensive transformers at either end of the line or incorporating new
electronics. You don't just buy a new cable. ;-)

Sure you do. Almost all "good" home-cinema (as well as middle-to-high-end
audio) equipment has both balanced and unbalanced ins and outs. (My
Parasound controller does. I use the unbalanced outputs to feed a Pioneer
quadrascope.)

 

[William Sommerwerck]

I've Googled, and as far as I can tell, there is no commercially available
device that converts cable-TV RF signals to optical, then back again. What
would be the point of such a device, when an isolation transformer would be
much, much cheaper?

On the other hand, there are hundreds of products that convert TOSlink to
coax and back again.

 

[Michael A. Terrell]

William Sommerwerck wrote:

I've Googled, and as far as I can tell, there is no commercially available
device that converts cable-TV RF signals to optical, then back again. What
would be the point of such a device, when an isolation transformer would be
much, much cheaper?

There is no reason. You can use a six hole Amidon core and make a
1:1 isolation transformer. Bytemark used to sell a lot of Amidon cores
and beads at hamfests, but their website has been gutted. I can't find
my Amidon Databook right now, but I'll see if I can locate it this
weekend.

You may find a suitable core in a junk two way 75 ohm TV splitter. The
Amidon website is useless, but the style would be like their
FB-61-5111-2.5, although type 64 core material would probably be better
than type 61. You can open a diecast splitter by shoving a sharp awl or
small screwdriver through the aluminum in one corner and peel the thin
aluminum back away from the conductive epoxy. If you can't find one, I
might still have some left from they 75 ohm return loss bridges I used
to build. They are out in the shop, and its still raining around here,
so it will be a day or two before I can check for you.

On the other hand, there are hundreds of products that convert TOSlink to
coax and back again.

--
You can't have a sense of humor, if you have no sense!

 

[William Sommerwerck]

I've Googled, and as far as I can tell, there is no commercially
available
device that converts cable-TV RF signals to optical, then back again.
What
would be the point of such a device, when an isolation transformer would
be
much, much cheaper?

There is no reason. You can use a six hole Amidon core and make a
1:1 isolation transformer. Bytemark used to sell a lot of Amidon cores
and beads at hamfests, but their website has been gutted. I can't find
my Amidon Databook right now, but I'll see if I can locate it this
weekend.

You may find a suitable core in a junk two way 75 ohm TV splitter. The
Amidon website is useless, but the style would be like their
FB-61-5111-2.5, although type 64 core material would probably be better
than type 61. You can open a diecast splitter by shoving a sharp awl or
small screwdriver through the aluminum in one corner and peel the thin
aluminum back away from the conductive epoxy. If you can't find one, I
might still have some left from they 75 ohm return loss bridges I used
to build. They are out in the shop, and it's still raining around here,
so it will be a day or two before I can check for you.

Thank you for your suggestions and kind offer. I'd appreciate your looking.

When I was putting together this device *, I opened the balun with a F plug
on one end and two screws (for the twinlead) on the other. ** The thought of
"rolling my own" crossed my mind. The whole thing verges on the trivial, the
"hard" part being firmly and stably attaching the F jack.

Two obvious questions...

1. Any particular type of wire if I want to get to 1GHz or beyond? (One
would think litz wire would be appropriate and needed.) Or can I just
cannibalize what's there?

2. Ditto for the number of turns. Same or less than the number in the
existing unit?


* I actually invented it 25 years ago, to resolve the same problem, but
that's another story.

** The other balun has a F jack on one end, twinlead with terminations on
the other end.

 

[Dave Plowman (News)]

In article <h2g34j$527$1@news.eternal-september.org>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

Er, either they're fitted with balanced connectors or they're not. To
modify an unbalanced unit isn't a trivial matter. Involves either using
expensive transformers at either end of the line or incorporating new
electronics. You don't just buy a new cable. ;-)

Sure you do. Almost all "good" home-cinema (as well as middle-to-high-end
audio) equipment has both balanced and unbalanced ins and outs. (My
Parasound controller does. I use the unbalanced outputs to feed a Pioneer
quadrascope.)

Total overkill. Balanced audio is only needed for very long runs or in
very hostile environments - not found in the home. Are your aerial and
video connections balanced?

--
*Income tax service - We‘ve got what it takes to take what you've got.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

William Sommerwerck wrote:

I've Googled, and as far as I can tell, there is no commercially
available
device that converts cable-TV RF signals to optical, then back again.
What
would be the point of such a device, when an isolation transformer would
be
much, much cheaper?

There is no reason. You can use a six hole Amidon core and make a
1:1 isolation transformer. Bytemark used to sell a lot of Amidon cores
and beads at hamfests, but their website has been gutted. I can't find
my Amidon Databook right now, but I'll see if I can locate it this
weekend.

You may find a suitable core in a junk two way 75 ohm TV splitter. The
Amidon website is useless, but the style would be like their
FB-61-5111-2.5, although type 64 core material would probably be better
than type 61. You can open a diecast splitter by shoving a sharp awl or
small screwdriver through the aluminum in one corner and peel the thin
aluminum back away from the conductive epoxy. If you can't find one, I
might still have some left from they 75 ohm return loss bridges I used
to build. They are out in the shop, and it's still raining around here,
so it will be a day or two before I can check for you.

Thank you for your suggestions and kind offer. I'd appreciate your looking.

When I was putting together this device *, I opened the balun with a F plug
on one end and two screws (for the twinlead) on the other. ** The thought of
"rolling my own" crossed my mind. The whole thing verges on the trivial, the
"hard" part being firmly and stably attaching the F jack.

Two obvious questions...

1. Any particular type of wire if I want to get to 1GHz or beyond? (One
would think litz wire would be appropriate and needed.) Or can I just
cannibalize what's there?

They use 36 to 40 AWG solid well past 1 GHz

2. Ditto for the number of turns. Same or less than the number in the
existing unit?

For best isolation I would use equal turns, a single wire for each side,
passing through three holes., each.

* I actually invented it 25 years ago, to resolve the same problem, but
that's another story.

** The other balun has a F jack on one end, twinlead with terminations on
the other end.

The problem with most baluns is that they wind two 75 Ohm windings as
a center tapped 300 Ohm transformer and feed the 75 Ohm to one winding,
and take the 300 Ohm off both windings and have the center tap grounded,
which provides no grounding. I used to buy fiber washers with a 3/8"
I.D. and a 1/2" O.D. from General Cement to isolate one jack from a
metal box. The other was connected to the box.


http://www.keyelco.com/products/specs/spec42.asp#three still carries
something similar as catalog number 3069 or 3241 The 3069 is 5/8" OD
for the washer part, while the 3241 is 3/4". I would use the 3241, to
give more fiber to compress.

Keystone is carried by a lot of distributors. I don't know if I
have any of the General Cement washers left. My last purchase was over
20 years ago.

<http://www.google.com/search?hl=en&rls=com.microsoft%3Aen-us&q=Keystone+3241+washer&btnG=Search&aq=f&oq=&aqi=>

'Authorized National Catalog Distributors':

Allied Electronics 800-433-5700 http://www.alliedelec.com/
Digi-Key Corp. 800-344-4539 http://www.digikey.com/
Mouser Electronics 800-346-6873 http://www.mouser.com/keystone
Newark InOne 800-463-9275 http://www.newarkinone.com/

or go to:
<http://www.keyelco.com/distributors/search_distributors.asp?Where=Domestic>
to find local wholesalers on a state by state basis.

I just looked at a damaged General Instruments four port tap with a
broken 'F' connector. It was replaced in front of my house the other day
because of an intermittent connection to a neighbor's house.. I see
they are using a smaller core for the transformer Typical center tapped
design, but tiny compared to the old 300 MHz version of the same tap.
It appears to have three intact 1:1 wound cores. If you'll e-mail me
with your street address, I'll pull a couple and mail them to you. Just
separate the center tap, and use those leads as the pair of 'grounds'.

Use a couple short pieces of 'component lead' (AKA tinned steel wire,
salvaged from a small resistor or capacitor) to connect them to the 'F'
connectors.

If I can get to it, I'll send you a small coil of surplus component
lead form the old Sprague capacitor factor in Orlando. I have a 20
pound spool, buried out in the shop somewhere.


--
You can't have a sense of humor, if you have no sense!