Noise radiation

Archived from groups: rec.audio.pro (More info?)

"Patrick Dunford"
> We have a sound desk that picks up buzz from three sources
> 1. Dimmers (very hard to get a single phase dimmer that we can put on
> another phase)
> 2. Data projector
> 3. Power amps
>


** Only requires to be correctly cabled and sited to stop all three.

Do you know what a balanced audio line is ??

How about what a hum loop is ???



BTW

Posting stupid whinges like this is really dumb.

Baaaaaaaaahhhhhhhhhhhh....



............... Phil

Archived from groups: rec.audio.pro (More info?)

"Carey Carlan"
> "Phil Allison"
>
>> Posting stupid whinges like this is really dumb.
>
> Patrick, Phil is our resident troll. Don't be upset by his remarks or
> respond to them.


** Whaaaat ?????

Do you mean to say I have serious competition here from some Kiwi sheep
shagger ????





....... Phil

Archived from groups: rec.audio.pro (More info?)

> BTW
>
> Posting stupid whinges like this is really dumb.
>
> Baaaaaaaaahhhhhhhhhhhh....
>
>
>
> .............. Phil

Phil, I believe posting "Baaaaaaaaahhhhhhhhhhhh" and berating remarks
are as you describe really dumb.

Paul

Archived from groups: rec.audio.pro (More info?)

In article <d98a2574.0410140907.2e61e1cf@posting.google.com> in
rec.audio.pro on 14 Oct 2004 10:07:22 -0700, Your Add Here!
<bluemt@earthlink.net> says...
> In my building there was radio frequency noise (ticking) bleeding into
> the gear (guitar amps especially). I used an AM radio to snoop around
> and found that there was a faulty wall wart in the dry cleaner's place
> next door that was being "broadcast" throughout through the wiring of
> the building. When I removed the 300mA transformar from the wall all
> my problems went away.

How was it faulty?

I'm galled that there is noise apparently coming from the power amps in
this system (big name gear)... either that or there is seriously
something wrong with the earthing in this building.

Archived from groups: rec.audio.pro (More info?)

"Patrick Dunford...
Phil Allison

>> > We have a sound desk that picks up buzz from three sources
>> > 1. Dimmers (very hard to get a single phase dimmer that we can put on
>> > another phase)
>> > 2. Data projector
>> > 3. Power amps
>> >
>>
>> ** Only requires to be correctly cabled and sited to stop all three.
>>
>> Do you know what a balanced audio line is ??
>
> Yes, I converted all the unbalanced lines between bits of gear into
> balanced.

> When we did the tests, there was no audio cabling connected between the
> sound desk and the power amps.


** So how did you hear anything - headphones ???


> As such any noise pickup must have been
> through the mains.


** Not at all - that is a wild assertion.

What makes you say that the power amps were causing the desk to buzz ?

Is the desk located very close to them or AC power cables in the premises.

Is there some big secret about the make and model of this desk ??



............. Phil

Archived from groups: rec.audio.pro (More info?)

Patrick Dunford wrote:

> In article <2t6tcpF1rj938U1@uni-berlin.de> in rec.audio.pro on Thu, 14
> Oct 2004 18:57:58 +1000, Phil Allison <philallison@tpg.com.au> says...
> >
> > "Patrick Dunford"
> > > We have a sound desk that picks up buzz from three sources
> > > 1. Dimmers (very hard to get a single phase dimmer that we can put on
> > > another phase)
> > > 2. Data projector
> > > 3. Power amps
> > >
> >
> >
> > ** Only requires to be correctly cabled and sited to stop all three.
> >
> > Do you know what a balanced audio line is ??
>
> Yes, I converted all the unbalanced lines between bits of gear into
> balanced.
>
> When we did the tests, there was no audio cabling connected between the
> sound desk and the power amps. As such any noise pickup must have been
> through the mains.

Not necessarily. You don't mention the make of console but old Neoteks for
example were sometimes in unscreened ( wooden ) enclosures IIRC. The mode of
transmission could then possibly be RF.

It's very rare for really bad interference to come up the power supply chain,
since voltages are normally well regulated in the console power supply. An
exception *might* be a as a result of very poor quality ground connection.

We really need to know more about the type and configuration of the equipment
before being able to make any informed comment.


Graham

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear"
> Patrick Dunford wrote:
>>
>> I'm galled that there is noise apparently coming from the power amps in
>> this system (big name gear)... either that or there is seriously
>> something wrong with the earthing in this building.
>
> What's the *big name(s)* ? Is there some kind of secret about your
> equipment
> ?


** Beware of anally retentive Kiwi trolls.


BTW The last time I heard a stupid whinge like this one was at the
Intercontinental Hotel in Sydney. It eventually turned out the Allen and
Heath 16 channel desk being maligned was sitting * right on top* of a 3
phase triac dimmer and power amp racks. The noise injection was straight
into the internal ribbon buss cable and thence all the virtual earth summing
stages.

Seems there was just nowhere else to put the damn desk.





............. Phil

Archived from groups: rec.audio.pro (More info?)

In article <416F11FD.549A5A86@hotmail.com> in rec.audio.pro on Fri, 15
Oct 2004 00:55:41 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> says...
> Patrick Dunford wrote:
>
> > In article <2t6tcpF1rj938U1@uni-berlin.de> in rec.audio.pro on Thu, 14
> > Oct 2004 18:57:58 +1000, Phil Allison <philallison@tpg.com.au> says...
> > >
> > > "Patrick Dunford"
> > > > We have a sound desk that picks up buzz from three sources
> > > > 1. Dimmers (very hard to get a single phase dimmer that we can put on
> > > > another phase)
> > > > 2. Data projector
> > > > 3. Power amps
> > > >
> > >
> > >
> > > ** Only requires to be correctly cabled and sited to stop all three.
> > >
> > > Do you know what a balanced audio line is ??
> >
> > Yes, I converted all the unbalanced lines between bits of gear into
> > balanced.
> >
> > When we did the tests, there was no audio cabling connected between the
> > sound desk and the power amps. As such any noise pickup must have been
> > through the mains.
>
> Not necessarily. You don't mention the make of console but old Neoteks for
> example were sometimes in unscreened ( wooden ) enclosures IIRC. The mode of
> transmission could then possibly be RF.
>
> It's very rare for really bad interference to come up the power supply chain,
> since voltages are normally well regulated in the console power supply. An
> exception *might* be a as a result of very poor quality ground connection.
>
> We really need to know more about the type and configuration of the equipment
> before being able to make any informed comment.

The desk is a Soundcraft Live4. Over the years there have been a lot of
noise problems, as a result of this the desk is currently being run off a
mains isolating transformer. The electricians at the time claimed there
was nothing wrong with the earthing of the sound power circuit or
building, and the fact that we could eliminate the problem by running a
long extension cord from the desk to the same plug as the power amps were
plugged into was just a coincidence.

Dimmers I can cope with, as the lamps can be run at full power which
results in no noise from the dimmer units. Most of the noise we were
getting from the projector and other bits of computer gear we eliminated
by running them off non-sound system power outlets and connecting them
all to the sound system with audio transformers. We just bought an Isomax
DM2-2PP for recording with, nice unit, good value.

Archived from groups: rec.audio.pro (More info?)

Patrick Dunford <patrickdunford@nomail.invalid> wrote:
>
>The desk is a Soundcraft Live4. Over the years there have been a lot of
>noise problems, as a result of this the desk is currently being run off a
>mains isolating transformer. The electricians at the time claimed there
>was nothing wrong with the earthing of the sound power circuit or
>building, and the fact that we could eliminate the problem by running a
>long extension cord from the desk to the same plug as the power amps were
>plugged into was just a coincidence.

Sounds to me like you have a ground loop between the desk and the amps,
then. But you say the problem persists even with the amplifiers unplugged
completely and the console used with headphones?

>Dimmers I can cope with, as the lamps can be run at full power which
>results in no noise from the dimmer units. Most of the noise we were
>getting from the projector and other bits of computer gear we eliminated
>by running them off non-sound system power outlets and connecting them
>all to the sound system with audio transformers. We just bought an Isomax
>DM2-2PP for recording with, nice unit, good value.

If you have a ground loop issue, it's best to fix it. THEN get your line
supply cleaned up so there isn't so much radiated noise around. Odds are
you have two separate problems and both need fixing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

Patrick Dunford wrote:

> The desk is a Soundcraft Live4. Over the years there have been a lot of
> noise problems, as a result of this the desk is currently being run off a
> mains isolating transformer.

That's not typical of the performance one would expect from a Live 4.

> The electricians at the time claimed there
> was nothing wrong with the earthing of the sound power circuit or
> building, and the fact that we could eliminate the problem by running a
> long extension cord from the desk to the same plug as the power amps were
> plugged into was just a coincidence.

Ahhh..... you didn't mention that you could eliminate the problem thus.

It pretty much *proves* that you have questionable wiring in your building.

Are your electricians work-shy by any chance ?

> Dimmers I can cope with, as the lamps can be run at full power which
> results in no noise from the dimmer units. Most of the noise we were
> getting from the projector and other bits of computer gear we eliminated
> by running them off non-sound system power outlets and connecting them
> all to the sound system with audio transformers. We just bought an Isomax
> DM2-2PP for recording with, nice unit, good value.

None of this should be necessary.


Graham

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> "Pooh Bear"
> > Patrick Dunford wrote:
>
> >
> >> The electricians at the time claimed there
> >> was nothing wrong with the earthing of the sound power circuit or
> >> building, and the fact that we could eliminate the problem by running a
> >> long extension cord from the desk to the same plug as the power amps were
> >> plugged into was just a coincidence.
> >
> > Ahhh..... you didn't mention that you could eliminate the problem thus.
> >
> > It pretty much *proves* that you have questionable wiring in your
> > building.
>
> ** Hardly - it just demonstrates that the earth conductors in a venue
> can have a small AC voltages imposed by magnetic induction or the fact there
> is more than one attachment point to the neutral.
>
> Remember, NZ like Australia uses the MEN ( multiple earth neutral ) system
> everywhere.

Which ends up sharing the neutral current between the neutral conductor and the
earth conductor.

I knew there was a reason I wasn't keen on it.

In that case maybe a *technical earth* would help ?


Graham

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> "Pooh Bear"
> > Phil Allison wrote:
> >>
> >> ** Hardly - it just demonstrates that the earth conductors in a
> >> venue
> >> can have a small AC voltages imposed by magnetic induction or the fact
> >> there
> >> is more than one attachment point to the neutral.
> >>
> >> Remember, NZ like Australia uses the MEN ( multiple earth neutral )
> >> system
> >> everywhere.
> >
> > Which ends up sharing the neutral current between the neutral conductor
> > and the
> > earth conductor.
>
> ** Not at all - the load current from each appliance returns entirely via
> the neutral wire. But where two fuse boards exist in a venue the earths
> from each will have slightly different AC potentials.

Because they're bonded at that point to the neutral conductor which has a load
related potential. I fail to see how, if there are multiple connections at
different potentials, how there can be *no* current flowing in the earth
conductor(s).


> > I knew there was a reason I wasn't keen on it.
>
> ** Nope - you just invented one like dumb the pommy ass you are.

See above - and btw - we don't get this problem in the UK where the earth is
referred separately back to the sub-station in most instances.


> > In that case maybe a *technical earth* would help ?
>
> ** More trouble and risk than any real benefit - removing ALL the damn
> ground loops from the system is the only fix likely to solve all noises at
> once.

It seems that MEN assures the possibility of ground loop problems.

V = IR and all that. If earths are at different potentials then it is because
there is a current flowing !


Graham

Archived from groups: rec.audio.pro (More info?)

In article <2t8g26F1t5o4mU1@uni-berlin.de> in rec.audio.pro on Fri, 15
Oct 2004 09:22:43 +1000, Phil Allison <philallison@tpg.com.au> says...
>
> "Patrick Dunford...
> Phil Allison
>
> >> > We have a sound desk that picks up buzz from three sources
> >> > 1. Dimmers (very hard to get a single phase dimmer that we can put on
> >> > another phase)
> >> > 2. Data projector
> >> > 3. Power amps
> >> >
> >>
> >> ** Only requires to be correctly cabled and sited to stop all three.
> >>
> >> Do you know what a balanced audio line is ??
> >
> > Yes, I converted all the unbalanced lines between bits of gear into
> > balanced.
>
> > When we did the tests, there was no audio cabling connected between the
> > sound desk and the power amps.
>
>
> ** So how did you hear anything - headphones ???
>
>
> > As such any noise pickup must have been
> > through the mains.
>
>
> ** Not at all - that is a wild assertion.
>
> What makes you say that the power amps were causing the desk to buzz ?
>
> Is the desk located very close to them or AC power cables in the premises.

The desk is roughly 20 metres away from the amps.

As for mains wiring, how is it possible to have any gear not "close" to
the wiring that it is plugged into for power???

Archived from groups: rec.audio.pro (More info?)

"Patrick Dunford"
Phil Allison ...

>> > As such any noise pickup must have been
>> > through the mains.
>>
>>
>> ** Not at all - that is a wild assertion.
>>
>> What makes you say that the power amps were causing the desk to buzz ?
>>
>> Is the desk located very close to them or AC power cables in the
>> premises.
>
> The desk is roughly 20 metres away from the amps.
>
> As for mains wiring, how is it possible to have any gear not "close" to
> the wiring that it is plugged into for power???
>


** Your desk ( Spirit Live 4 ) has a remote PSU feeding only DC current
down the wires - so there is no possibility of noise injection from that.
All your symptoms resemble earth loop injection.

A desk might be placed anywhere, on top of dimmers for example or up
against a wall that has high current AC wiring attached close by or just
inside the wall.




.............. Phil

Archived from groups: rec.audio.pro (More info?)

"Patrick Dunford"

>>
>> ** Exactly how ground loops behave.
>>
>> How dumb.
>
> All of the sound gear is powered off a dedicated feed that has only one
> earth connection at the switchboard.


** Not even slightly related to whether you have ground loops in your
SYSTEM !!

How dumb.



........... Phil

Archived from groups: rec.audio.pro (More info?)

In article <2th3qpF1ve015U1@uni-berlin.de> in rec.audio.pro on Mon, 18
Oct 2004 15:49:15 +1000, Phil Allison <philallison@tpg.com.au> says...
>
> "Patrick Dunford"
>
> >>
> >> ** Exactly how ground loops behave.
> >>
> >> How dumb.
> >
> > All of the sound gear is powered off a dedicated feed that has only one
> > earth connection at the switchboard.
>
>
> ** Not even slightly related to whether you have ground loops in your
> SYSTEM !!
>
> How dumb.


You're a liar, ground looping is related to the common practice of having
gear plugged into different power outlets that each have their own
indivudual earth connection at the switchboard. Due to the way that most
mains wiring is carried out, in which sockets are wired typically two to
a 15A circuit every pair of outlets has its own separate earth wire going
back to the switchboard.

So the fact of the matter is that having only one earth path back to the
switchboard is vitally relevant to the ground loop issue. Everyone knows
that if all your gear is plugged into the same power outlet, even if you
have to use long extension cords, that you will not get a ground loop.

Archived from groups: rec.audio.pro (More info?)

In article <4175CAB2.FC7984EC@hotmail.com> in rec.audio.pro on Wed, 20
Oct 2004 03:17:22 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> says...
>
>
> Phil Allison wrote:
>
> > "Pooh Bear"
> > > Phil Allison wrote:
> >
> > >>
> > >> ** Not at all - the load current from each appliance returns entirely
> > >> via
> > >> the neutral wire. But where two fuse boards exist in a venue the earths
> > >> from each will have slightly different AC potentials.
> > >
> > > Because they're bonded at that point to the neutral conductor which has a
> > > load
> > > related potential. I fail to see how, if there are multiple connections at
> > > different potentials, how there can be *no* current flowing in the earth
> > > conductor(s).
> >
> > ** You have got it ALL wrong.
> >
> > A string of AC outlets should only be connected to the fuse box earth buss
> > once - but sometimes a loop gets formed by accident in large installations
> > like venues.
>
> Yup. I kind of guessed that it *shouldn't* typically happen but multiple supply
> boards will assuredly cause this kind of problem.
>
>
> > The name MEN refers to the fact that the supply neutral is connected to an
> > earth stake ( or cold water pipes in the past ) at every premises in a
> > street.
>
> In which case it would appear to be similar but maybe not quite the same as the
> UK MPE ( multiple protective earthing ) system.
>
> I did a quick google on this at google.co.uk restricted to Uk results and got
> some results referring the the IEE 16th edition regulations if you're
> interested.
>
> http://www.google.co.uk/search?hl= [...] CcountryGB
>
> > >> > In that case maybe a *technical earth* would help ?
> > >>
> > >> ** More trouble and risk than any real benefit - removing ALL the
> > >> damn
> > >> ground loops from the system is the only fix likely to solve all noises
> > >> at
> > >> once.
> > >
> > > It seems that MEN assures the possibility of ground loop problems.
> >
> > ** Nope - they are already assured with any audio system that has multiple
> > connections to the AC supply ground spread over an area. Magnetic induction
> > create currents in such loops and the more the area the worse.
> >
> > Only the biggest dopes do what the OP did and use widely spaced AC outlets
> > for the desk and amp racks thereby creating a MONSTER area earth loop. Such
> > a loop in a live music venue will be riddled with dimmer buzz etc -
> > possibly hundreds of millivolts worth.
>
> Intruigingly I've *never* ever personally experienced anything like these kind
> of problems in all my years ( of old ) of running PA systems for hire. Just
> lucky maybe ?

No, the fact is, having the amps some distance away from the desk is very
common practice - and causes no problems 99.9% of the time.

Archived from groups: rec.audio.pro (More info?)

In article <cl6029$cpe$1@panix2.panix.com> in rec.audio.pro on 20 Oct
2004 11:26:01 -0400, Scott Dorsey <kludge@panix.com> says...

> No, you can still get loops caused by multiple _signal_ grounds as well.
>
> Plugging everything into the same power outlet just reduces the size of
> the loop, it does not eliminate it. You still have multiple ground paths,
> they are just closer together and therefore less apt to get noise induced
> in them.
>
> There is no substitute for a proper grounding scheme where every piece of
> equipment has one and only one ground path to every other piece of equipment.

Or, in other words

Every piece of gear must be connected by balanced connections with the
shield disconnected, or through an audio transformer, especially with
unbalanced connections.

Which the better house systems I have seen design into place - every line
from the desk to the amps has a transformer in it.

But in this case, only the mains earth connection between the pieces of
gear, no audio lines connected at all, hmmmmm...

> There are even occasional problems with internal ground loops generated
> inside a piece of equipment. This is increasingly common, and there is an
> AES paper on the "Pin 1 problem" out there.

It's covered in Jensen Transformer's website application notes I think.