Railway line interference

[Gareth Magennis]

Hi,

just done a gig where there was an unusual problem with a guitar.
There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), which, when put through the PA or
monitors, actually fed back uncontrollably into a continuous tone. It
sounded like some kind of radio transmission, or mobile phone, but it was a
continuous fixed signal.

I've heard something similar before in a building that had a hearing aid
loop fitted and active, so asked the venue manager if he knew of any
transmitting devices in the building. He informed me that they had had this
problem before, and it was the high voltage power lines on the railway above
the venue that was the culprit. (The venue is in the arches beneath the
approach to London Bridge Station).

This got me thinking - the base frequency seemed to be around the "E" above
middle C, (330Hz) with loads of harmonics - no chance of filtering it out,
even though I gave it a go. Probably close to a square wave or a digital
datastream at that frequency.
High voltage lines I presume are DC, so I would guess this would have to be
coming from signals.
But why would signals be powered so high as to cause this kind of (almost
impossible to play) interference?

A bit of Googling shows that some types of train detection circuits use AC
in the audio range
http://en.wikipedia.org/wiki/Track_circuit

but why would it need to be so large as to cause this amount of
interference?

Or is this actually a radio communications thing instead?



Cheers,


Gareth.

[Phil Allison]

"Gareth Magennis"

Post by Gareth Magennis
just done a gig where there was an unusual problem with a guitar.
There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), which, when put through the PA
or monitors, actually fed back uncontrollably into a continuous tone. It
sounded like some kind of radio transmission, or mobile phone, but it was
a continuous fixed signal.
I've heard something similar before in a building that had a hearing aid
loop fitted and active, so asked the venue manager if he knew of any
transmitting devices in the building. He informed me that they had had
this problem before, and it was the high voltage power lines on the
railway above the venue that was the culprit. (The venue is in the arches
beneath the approach to London Bridge Station).
This got me thinking - the base frequency seemed to be around the "E"
above middle C, (330Hz) with loads of harmonics - no chance of filtering
it out, even though I gave it a go. Probably close to a square wave or a
digital datastream at that frequency.
High voltage lines I presume are DC, so I would guess this would have to
be coming from signals.

** It may well be coming from the high voltage DC lines just as you were
informed.

How do you think the DC power is derived ? From batteries ??

Of course it comes from rectifying the AC 3 phase supply.

With full wave rectification, no filtering is needed and the ripple
frequency 6 times the wave frequency - so 300Hz ( plus harmonics) in a 50
Hz system.

http://en.wikipedia.org/wiki/File:3_phase_rectification_2.svg



.... Phil

[Gareth Magennis]

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
just done a gig where there was an unusual problem with a guitar.
There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), which, when put through the PA
or monitors, actually fed back uncontrollably into a continuous tone. It
sounded like some kind of radio transmission, or mobile phone, but it was
a continuous fixed signal.
I've heard something similar before in a building that had a hearing aid
loop fitted and active, so asked the venue manager if he knew of any
transmitting devices in the building. He informed me that they had had
this problem before, and it was the high voltage power lines on the
railway above the venue that was the culprit. (The venue is in the
arches beneath the approach to London Bridge Station).
This got me thinking - the base frequency seemed to be around the "E"
above middle C, (330Hz) with loads of harmonics - no chance of
filtering it out, even though I gave it a go. Probably close to a square
wave or a digital datastream at that frequency.
High voltage lines I presume are DC, so I would guess this would have to
be coming from signals.

** It may well be coming from the high voltage DC lines just as you were
informed.
How do you think the DC power is derived ? From batteries ??
Of course it comes from rectifying the AC 3 phase supply.
With full wave rectification, no filtering is needed and the ripple
frequency 6 times the wave frequency - so 300Hz ( plus harmonics) in a 50
Hz system.
http://en.wikipedia.org/wiki/File:3_phase_rectification_2.svg
.... Phil

I've got a recording of the gig which I will listen to tonight and see if I
can hear it anywhere and post a sample somewhere - I'm pretty sure it was an
"E" though.
(Thats partly why it was so confusing at first, being pretty much in tune
with the guitar).

I've never heard 3 phase "ripple" to my knowledge, but this just didn't
sound like mains, but very much like a radio signal.


Cheers,


Gareth.

[Phil Allison]

"Gareth Magennis"

"Phil Allison"

Post by Phil Allison
** It may well be coming from the high voltage DC lines just as you were
informed.
How do you think the DC power is derived ? From batteries ??
Of course it comes from rectifying the AC 3 phase supply.
With full wave rectification, no filtering is needed and the ripple
frequency 6 times the wave frequency - so 300Hz ( plus harmonics) in a
50 Hz system.
http://en.wikipedia.org/wiki/File:3_phase_rectification_2.svg

I've got a recording of the gig which I will listen to tonight and see if
I can hear it anywhere and post a sample somewhere - I'm pretty sure it
was an "E" though.
(Thats partly why it was so confusing at first, being pretty much in tune
with the guitar).
I've never heard 3 phase "ripple" to my knowledge,

** Frankly, neither have I.

What you heard was highly modified by the guitar PU and the signal
processing following it.

I expect it would sound quite sci-fi and weird.

but this just didn't sound like mains, but very much like a radio signal.

** Bollocks.



... Phil

[Gareth Magennis]

Post by Phil Allison
"Gareth Magennis"

"Phil Allison"

Post by Phil Allison
** It may well be coming from the high voltage DC lines just as you were
informed.
How do you think the DC power is derived ? From batteries ??
Of course it comes from rectifying the AC 3 phase supply.
With full wave rectification, no filtering is needed and the ripple
frequency 6 times the wave frequency - so 300Hz ( plus harmonics) in a
50 Hz system.
http://en.wikipedia.org/wiki/File:3_phase_rectification_2.svg

I've got a recording of the gig which I will listen to tonight and see if
I can hear it anywhere and post a sample somewhere - I'm pretty sure it
was an "E" though.
(Thats partly why it was so confusing at first, being pretty much in tune
with the guitar).
I've never heard 3 phase "ripple" to my knowledge,

** Frankly, neither have I.
What you heard was highly modified by the guitar PU and the signal
processing following it.
I expect it would sound quite sci-fi and weird.

but this just didn't sound like mains, but very much like a radio signal.

** Bollocks.
... Phil

Well you're probably right, he had ten tons of FX going on.
Hope I've captured a sample.


Gareth.

[Arny Krueger]

Post by Gareth Magennis
I've never heard 3 phase "ripple" to my knowledge, but this just didn't
sound like mains, but very much like a radio signal.

The CW radar sets I worked on back in the 60s were powered by 400 Hz 3
phase, and there was 2400 Hz noise all over the place. They screamed!
Substantial amounts of power were involved, and the transformer core
magnetostriction acoustical noise was there, even if the circuitry was
electrically quiet.

[r***@hotmail.com]

Post by Arny Krueger

Post by Gareth Magennis
I've never heard 3 phase "ripple" to my knowledge, but this just didn't
sound like mains, but very much like a radio signal.

The CW radar sets I worked on back in the 60s were powered by 400 Hz 3
phase, and there was 2400 Hz noise all over the place. They screamed!
Substantial amounts of power were involved, and the transformer core
magnetostriction acoustical noise was there, even if the circuitry was
electrically quiet.

Everything on the train is powered by 400 hz, 3phase power, if it's a
passenger train, but that is only ON the train. If the train is
electric it is powered by DC or mains frequency AC. Some lines on the
former Pennsy are STILL 25 Hz, but not many.

Aircraft and submarines are also 400 Hz.

[Phil Allison]

"Gareth Magennis"

(The venue is in the arches beneath the approach to London Bridge
Station).

** This one ?

http://www.arcadia-london.com/



... Phil

[Peter Larsen]

[about railway line interference]

A girlfriend lived (lives) next to the (elevated) main railway line out of
Copenhagen, and yes, railways, locomotives, signalsystems, whatever are RFI
noisy, it took cable fm to get technically good FM reception there, it was
not a sonic improvement due to the cable supplier using as many ad-da steps
as possible and then some, but that's a different tale.

Try to find an AM radio and listen "off station" in the location you
encountered the problem in.

Gareth

Kind regards

Peter Larsen

[Ty Ford]

Post by Peter Larsen

[about railway line interference]

A girlfriend lived (lives) next to the (elevated) main railway line out of
Copenhagen, and yes, railways, locomotives, signalsystems, whatever are RFI
noisy, it took cable fm to get technically good FM reception there, it was
not a sonic improvement due to the cable supplier using as many ad-da steps
as possible and then some, but that's a different tale.
Try to find an AM radio and listen "off station" in the location you
encountered the problem in.

I had a fellow engineer ask about rfi after they put in the Light Rail, train
tracks. He was using dynamic mics, the Sennheiser 421, as I recall.

After years of "no problem", suddenly he had all sorts of rfi. We were not
able to confirm it was signaling that had been added along the electric rail
lines, but I'm guessing that's what it was. The coil in the 421 was acting
like an antenna. He went to a condenser mic and the problem went away.

Regards,

Ty Ford


--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar

[bob urz]

Post by Ty Ford

Post by Peter Larsen

[about railway line interference]

A girlfriend lived (lives) next to the (elevated) main railway line out of
Copenhagen, and yes, railways, locomotives, signalsystems, whatever are RFI
noisy, it took cable fm to get technically good FM reception there, it was
not a sonic improvement due to the cable supplier using as many ad-da steps
as possible and then some, but that's a different tale.
Try to find an AM radio and listen "off station" in the location you
encountered the problem in.

I had a fellow engineer ask about rfi after they put in the Light Rail, train
tracks. He was using dynamic mics, the Sennheiser 421, as I recall.
After years of "no problem", suddenly he had all sorts of rfi. We were not
able to confirm it was signaling that had been added along the electric rail
lines, but I'm guessing that's what it was. The coil in the 421 was acting
like an antenna. He went to a condenser mic and the problem went away.
Regards,
Ty Ford
--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar http://youtu.be/yWaPRHMGhGA

Had a RFI problem in a church once that was strange. Direct boxes and
certain mikes would pick up a hash. I switched out the front end mixers
with little change. A little sleuthing turned out that this noise was
dimmer level dependent. It turned out the feeder for the sanctuary
light dimmers was buried in a slab under the area having issues.
I used a 58 as a witching stick to confirm where it was. Some
condenser mikes, FET direct boxes and different mike placement reduced
the issue

bob

[Ty Ford]

Post by bob urz
Had a RFI problem in a church once that was strange. Direct boxes and
certain mikes would pick up a hash. I switched out the front end mixers
with little change. A little sleuthing turned out that this noise was
dimmer level dependent. It turned out the feeder for the sanctuary
light dimmers was buried in a slab under the area having issues.
I used a 58 as a witching stick to confirm where it was. Some
condenser mikes, FET direct boxes and different mike placement reduced
the issue
bob

HNY Bob,

I had issues with residential dimmers and, yes, anyway but off or all the way
up in those SCR-based dimmers can be quite noisy.

I've been trying Router Motor COntrol boxes from Harbor Freight and find they
do a quieter job.

Regards,

Ty Ford

--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar http://youtu.be/yWaPRHMGhGA

[geoff]

Post by Ty Ford
After years of "no problem", suddenly he had all sorts of rfi. We
were not able to confirm it was signaling that had been added along
the electric rail lines, but I'm guessing that's what it was. The
coil in the 421 was acting like an antenna. He went to a condenser
mic and the problem went away.

Also maybe relevant is that the DC-powered (and AC for that matter) use
EARTH RETURN, so there maybe well be large earth-currents in the vicinity.

geoff

[Gareth Magennis]

Here's a clip of the Interference - almost a perfect "E".


http://kiwi6.com/file/u5i1i5x53g


Gareth.

[Peter Larsen]

Post by Gareth Magennis
Here's a clip of the Interference - almost a perfect "E".
http://kiwi6.com/file/u5i1i5x53g

Hmm .... my physioterapeut has moved their gym to a new room in the same
building and have some fancy dimming installed on fluorescents .... reckon
it has to be some kind of wavechopping.

Post by Gareth Magennis
Gareth

Kind regards

Peter Larsen

[Gareth Magennis]

Post by Peter Larsen

Post by Gareth Magennis
Here's a clip of the Interference - almost a perfect "E".
http://kiwi6.com/file/u5i1i5x53g

Hmm .... my physioterapeut has moved their gym to a new room in the same
building and have some fancy dimming installed on fluorescents .... reckon
it has to be some kind of wavechopping.

Post by Gareth Magennis
Gareth

Kind regards
Peter Larsen

I am starting to wonder if this is in fact a mains borne issue, and the
whole railway line explanation a red herring or possibly a way for the menu
manager to pass the buck.

Taking a scope to the gig is going to be a pain in the arse though.


Cheers,

Gareth.

[Phil Allison]

"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!

Quote:

" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "

So it is EMI * radiated into the air* and received by the coil of the PU.

Then MASSIVELY amplified by all the processing crap that was hanging off it.

Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.



... Phil

[Denny Strauser]

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

Single coil pickups are not the only culprits. Piezo pickups & cheap
pedals can introduce the same interference into the signal, as well as a
poorly grounded send snake.

There is an outdoor amphitheater here in Pittsburgh that constantly had
a problem with a nearby AM/FM radio tower antenna. I've worked with so
many sound engineers that thought they could fix the problem .... but
not one was able to eliminate the radio signal from the sound system.

But, it was fun watching these experts fail.

- Denny

[Phil Allison]

"Denny Strauser "

Post by Denny Strauser

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

Single coil pickups are not the only culprits.

** They **ARE** the only ones in the example in question.

Single coil PUs ARE at least 1000 times more sensitive to ( audio
frequency) magnetic fields than anything else connected to a PA system.

Fuck off to hell !!!!!!!!!

YOU bullshitting, pig ignorant, psycho fuckwit.




.... Phil

[Arkansan Raider]

Why, good morning Phil!

Coffee?

---Jeff

[Denny Strauser]

"Denny Strauser"

Post by Denny Strauser

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

Single coil pickups are not the only culprits.

** They **ARE** the only ones in the example in question.
Single coil PUs ARE at least 1000 times more sensitive to ( audio
frequency) magnetic fields than anything else connected to a PA system.
Fuck off to hell !!!!!!!!!
YOU bullshitting, pig ignorant, psycho fuckwit.
.... Phil

You snipped my post, Phil. Is not this one of your biggest complaints
about this newsgroup? If the readers would step back through this
thread, I'd absolutely love watching Phil to try working his way around
the RFI problem I mentioned (& Phil snipped) in this thread.

- Denny

[Denny Strauser]

Post by Phil Allison
Fuck off to hell !!!!!!!!!
YOU bullshitting, pig ignorant, psycho fuckwit.
.... Phil

I would love to see Phil under a real-life live-sound situation.
The Promoter screaming about why the soundcheck held up doors opening.
The Tour Manager is pissed at the Promoter because the red M&M's weren't
removed.
The Club Owner is pissed, because no one showed up, & he's losing money.
And, as they say ... $HIT runs downhill.
I'd love to see how some would deal with this very real situation.
- Denny

[geoff]

Post by Denny Strauser

Post by Phil Allison
Fuck off to hell !!!!!!!!!
YOU bullshitting, pig ignorant, psycho fuckwit.
.... Phil

I would love to see Phil under a real-life live-sound situation.
The Promoter screaming about why the soundcheck held up doors opening.
The Tour Manager is pissed at the Promoter because the red M&M's
weren't removed.
The Club Owner is pissed, because no one showed up, & he's losing
money. And, as they say ... $HIT runs downhill.
I'd love to see how some would deal with this very real situation.

There would be no problem. He'd have already told the useless (and
doubtlessly assinine, or even assiten) audience to piss off home.

geoff

[geoff]

Post by Denny Strauser
Single coil pickups are not the only culprits. Piezo pickups & cheap
pedals can introduce the same interference into the signal, as well
as a poorly grounded send snake.
There is an outdoor amphitheater here in Pittsburgh that constantly
had a problem with a nearby AM/FM radio tower antenna. I've worked
with so many sound engineers that thought they could fix the problem
.... but not one was able to eliminate the radio signal from the
sound system.

If you a near a electric-traction substation, the rectifiers can produce
mucho crap (though probably a lot better now than yesteryear). Over 25
years ago part of my job was maintaining the remote-control gear for our
local suburban DC train system. REEEAALLLY impressive when a rail unit
started up in the sector, watching those huge mecury-arc rectifier tubes
spring into life.....

geoff

[Denny Strauser]

Post by geoff

Single coil pickups are not the only culprits. Piezo pickups& cheap
pedals can introduce the same interference into the signal, as well
as a poorly grounded send snake.
There is an outdoor amphitheater here in Pittsburgh that constantly
had a problem with a nearby AM/FM radio tower antenna. I've worked
with so many sound engineers that thought they could fix the problem
.... but not one was able to eliminate the radio signal from the
sound system.

If you a near a electric-traction substation, the rectifiers can produce
mucho crap (though probably a lot better now than yesteryear). Over 25
years ago part of my job was maintaining the remote-control gear for our
local suburban DC train system. REEEAALLLY impressive when a rail unit
started up in the sector, watching those huge mecury-arc rectifier tubes
spring into life.....
geoff

I actually brought up this topic on ProSoundWeb a few years ago. Unless
this interference is in the line current itself, and just one or more
sound system components have poor power supplies ....... then ...... if
it is due to just a few sources onstage, some of these problems can be
eliminated with ferrites. These are the cylindrical collars that you
will see on many computer cables. And, I've been told (but have not yet
tried), if a single coil pickup guitar cable is wrapped around a steel
mic stand a few times, it acts as a choke & eliminates much EMI/RFI.

I'm wearing my flame retardant suit, Phil.

- Denny

[Lord Valve]

Post by Denny Strauser
. And, I've been told (but have not yet
tried), if a single coil pickup guitar cable is wrapped around a steel
mic stand a few times, it acts as a choke & eliminates much EMI/RFI.

Absolutely true, and I've used the technique.

I was doing an install (DJ booth) in a joint that was
basically right underneath a huge radio tower
(base of the tower was maybe 150 feet from the
club's back door) and the only way I could get
the damn station out of the audio was to wrap
the DJ's mike line (balanced lo-z!) four times
around the center post of a bar table, which
was a piece of 4" pipe. Worked like a charm.


Lord Valve
Asshole

[Gareth Magennis]

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.
... Phil

Hmm, well the reason I said this is because of Peter Larsen's post, which
was the one I was responding to.

If he recognised the audio sample I posted as one of "wavechopping", then I
will indeed take this seriously, and look at the problem differently.
(In hindsight, I don't think he actually posted this recogntion
specifically - my bad, maybe).

It is not beyond the realms of possibility, though, that more than one
factor is contributing to the symptoms experienced.

This interference has not happened before, the railway has been there for
quite some time now - the addition of some "wavechopping" equipment onto the
mains supply could in some way be contributing to the effect observed (e.g.
the guitarists FX units power supply may now be contaminated with all kinds
of shite, which may interact with or modulate a different kind of shite
being picked up by the single coil pickups).


Cheers,


Gareth.

[Phil Allison]

"Gareth Magennis"

"Phil Allison"

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
I am starting to wonder if this is in fact a mains borne issue,

** Course it is NOT mains borne - you steaming, great fuckwit !!
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

Hmm, well the reason I said this is because of Peter Larsen's post, which
was the one I was responding to.
If he recognised the audio sample I posted as one of "wavechopping",

** Horse poop.

[Peter Larsen]

Post by Gareth Magennis

Post by Phil Allison
" There seemed to be some kind of signal picked up by the (single
coil) pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.
... Phil

When Phil comes on like that you must be prepared to handle the risk that he
is right, he admittedly often is.

Post by Gareth Magennis
Hmm, well the reason I said this is because of Peter Larsen's post,
which was the one I was responding to.
If he recognised the audio sample I posted as one of "wavechopping",
then I will indeed take this seriously, and look at the problem
differently. (In hindsight, I don't think he actually posted this
recogntion specifically - my bad, maybe).

Whenever you have RFI then it can be helpful to bring a scope. And it is
possibly a good idea to go there at 11 am and check things. If there is
something mains-driven that emits RFI then it is makes sense to me that the
RFI should also be visible overlaid the mains voltage. That does NOT PREVENT
IT FROM ENTERING PICKUPS DIRECTLY PHIL, but it make it simpler to pinpoint
it. And the interference sounds just like the triac noise that entered my
ReVox A77HS from a light desk 3 feet from it except that the frequency is
higher. THAT is my reason for posting the asumption that it correlates with
something that chops mains voltage, dimmers for fluorescents in my
understanding - YO PHIL POMMYLOT, THIS IS WHERE YOUR KNOWHOW WOULD BE WELL
APPLIED - do that.

Post by Gareth Magennis
It is not beyond the realms of possibility, though, that more than one
factor is contributing to the symptoms experienced.
This interference has not happened before, the railway has been there
for quite some time now - the addition of some "wavechopping"
equipment onto the mains supply could in some way be contributing to
the effect observed (e.g. the guitarists FX units power supply may
now be contaminated with all kinds of shite, which may interact with
or modulate a different kind of shite being picked up by the single
coil pickups).

Troubleshooting question 1: did it ever work

Troubleshooting question 2: what changed

Go get Pease's book on troubleshooting analog circuits, nobody here should
be without it!

Post by Gareth Magennis
Gareth

Kind regards - also to Phil

Peter Larsen

[Gareth Magennis]

Post by Peter Larsen

Post by Gareth Magennis

Post by Phil Allison
" There seemed to be some kind of signal picked up by the (single
coil) pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.
... Phil

When Phil comes on like that you must be prepared to handle the risk that
he is right, he admittedly often is.

Post by Gareth Magennis
Hmm, well the reason I said this is because of Peter Larsen's post,
which was the one I was responding to.
If he recognised the audio sample I posted as one of "wavechopping",
then I will indeed take this seriously, and look at the problem
differently. (In hindsight, I don't think he actually posted this
recogntion specifically - my bad, maybe).

Whenever you have RFI then it can be helpful to bring a scope. And it is
possibly a good idea to go there at 11 am and check things. If there is
something mains-driven that emits RFI then it is makes sense to me that
the RFI should also be visible overlaid the mains voltage. That does NOT
PREVENT IT FROM ENTERING PICKUPS DIRECTLY PHIL, but it make it simpler to
pinpoint it. And the interference sounds just like the triac noise that
entered my ReVox A77HS from a light desk 3 feet from it except that the
frequency is higher. THAT is my reason for posting the asumption that it
correlates with something that chops mains voltage, dimmers for
fluorescents in my understanding - YO PHIL POMMYLOT, THIS IS WHERE YOUR
KNOWHOW WOULD BE WELL APPLIED - do that.

Post by Gareth Magennis
It is not beyond the realms of possibility, though, that more than one
factor is contributing to the symptoms experienced.
This interference has not happened before, the railway has been there
for quite some time now - the addition of some "wavechopping"
equipment onto the mains supply could in some way be contributing to
the effect observed (e.g. the guitarists FX units power supply may
now be contaminated with all kinds of shite, which may interact with
or modulate a different kind of shite being picked up by the single
coil pickups).

Troubleshooting question 1: did it ever work
Troubleshooting question 2: what changed
Go get Pease's book on troubleshooting analog circuits, nobody here should
be without it!

Post by Gareth Magennis
Gareth

Kind regards - also to Phil
Peter Larsen

The troubleshooting here is compounded by the fact that we do not know the
history of the guitarists gear. It could actually be faulty or poorly
screened.

He only appeared the once, and is unlikely to appear again, though the venue
manager did say this problem has arisen before. (Perhaps by another
guitarist with poor gear, perhaps not).


Cheers,

Gareth.

[Phil Allison]

"Gareth Magennis = MORONIC CUNT

Post by Gareth Magennis
The troubleshooting here is compounded by the fact that we do not know the
history of the guitarists gear. It could actually be faulty or poorly
screened.

** Listen - you FUCKING TENTH WITTED MORON !!

Did YOU write this or fucking NOT ??????


" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), which, when put through the PA or
monitors, actually fed back uncontrollably into a continuous tone."

Do you recall this inspired analysis:

" Single coil PUs ARE at least 1000 times more sensitive to ( audio
frequency) magnetic fields than anything else connected to a PA system.

Fuck off to hell !!!!!!!!!

YOU bullshitting, pig ignorant, psycho fuckwit. "


Shit like you should be served up to pigs for breakfast.




.... Phil

[Gareth Magennis]

Post by Phil Allison
"Gareth Magennis = MORONIC CUNT

Post by Gareth Magennis
The troubleshooting here is compounded by the fact that we do not know
the history of the guitarists gear. It could actually be faulty or
poorly screened.

** Listen - you FUCKING TENTH WITTED MORON !!
Did YOU write this or fucking NOT ??????
" There seemed to be some kind of signal picked up by the (single coil)
pickups, (FX board but no backline amp), which, when put through the PA or
monitors, actually fed back uncontrollably into a continuous tone."
" Single coil PUs ARE at least 1000 times more sensitive to ( audio
frequency) magnetic fields than anything else connected to a PA system.
Fuck off to hell !!!!!!!!!
YOU bullshitting, pig ignorant, psycho fuckwit. "
Shit like you should be served up to pigs for breakfast.
.... Phil

Any idea where this 330 Hz is coming from?


Cheers,


Gareth.

[Arkansan Raider]

Ah, yes. The Phil we've all come to know and love.

You want some coffee, bud? I've plenty to share.

---Jeff

[Gareth Magennis]

Post by Peter Larsen

Post by Gareth Magennis

Post by Phil Allison
" There seemed to be some kind of signal picked up by the (single
coil) pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.
... Phil

When Phil comes on like that you must be prepared to handle the risk that
he is right, he admittedly often is.

Post by Gareth Magennis
Hmm, well the reason I said this is because of Peter Larsen's post,
which was the one I was responding to.
If he recognised the audio sample I posted as one of "wavechopping",
then I will indeed take this seriously, and look at the problem
differently. (In hindsight, I don't think he actually posted this
recogntion specifically - my bad, maybe).

Whenever you have RFI then it can be helpful to bring a scope. And it is
possibly a good idea to go there at 11 am and check things. If there is
something mains-driven that emits RFI then it is makes sense to me that
the RFI should also be visible overlaid the mains voltage. That does NOT
PREVENT IT FROM ENTERING PICKUPS DIRECTLY PHIL, but it make it simpler to
pinpoint it. And the interference sounds just like the triac noise that
entered my ReVox A77HS from a light desk 3 feet from it except that the
frequency is higher. THAT is my reason for posting the asumption that it
correlates with something that chops mains voltage, dimmers for
fluorescents in my understanding - YO PHIL POMMYLOT, THIS IS WHERE YOUR
KNOWHOW WOULD BE WELL APPLIED - do that.

Post by Gareth Magennis
It is not beyond the realms of possibility, though, that more than one
factor is contributing to the symptoms experienced.
This interference has not happened before, the railway has been there
for quite some time now - the addition of some "wavechopping"
equipment onto the mains supply could in some way be contributing to
the effect observed (e.g. the guitarists FX units power supply may
now be contaminated with all kinds of shite, which may interact with
or modulate a different kind of shite being picked up by the single
coil pickups).

Troubleshooting question 1: did it ever work
Troubleshooting question 2: what changed
Go get Pease's book on troubleshooting analog circuits, nobody here should
be without it!

Post by Gareth Magennis
Gareth

Kind regards - also to Phil
Peter Larsen

If this is in fact some kind of Triac switching noise, what could be
switching at 330Hz?

Phil previously mentioned that 3 phase switching/ripple would be occuring at
300Hz. (6 x nominal frequency)

Power generation by railways is, from my limited Googling, also at 50 or
60Hz, probably not taken from the National Grid, but required to be a fixed
known frequency all the same.



Gareth.

[Phil Allison]

"Peter Larsen= BULLSHITTING IDIOT "

Post by Peter Larsen

"Phil Allison"

Post by Phil Allison
" There seemed to be some kind of signal picked up by the (single
coil) pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

When Phil comes on like that you must be prepared to handle the risk that
he is right, he admittedly often is.

** And YOU never are - fuckhead.

Post by Peter Larsen
Whenever you have RFI

** There is no Radio Frequency involved - fuckwit !!!

The term is EMI = Electro Magnetic Interference !!!!

Post by Peter Larsen
there is something mains-driven that emits RFI then it is makes sense to
me that the RFI should also be visible overlaid the mains voltage.

** Why do you keep using the WRONG term ??

Post by Peter Larsen
That does NOT PREVENT IT FROM ENTERING PICKUPS DIRECTLY PHIL,

** Guitar pickup do not respond to RFI - fuckwit.

Guitar pickups do not respond to mains borne EMI either.

FYI " mains borne interference " = interference carried into equipment
by mains cabling.

BTW fluoro dimming is NOT done at audio frequencies.


... Phil

[Gareth Magennis]

Post by Phil Allison
"Peter Larsen= BULLSHITTING IDIOT "

Post by Peter Larsen

"Phil Allison"

Post by Phil Allison
" There seemed to be some kind of signal picked up by the (single
coil) pickups, (FX board but no backline amp), "
So it is EMI * radiated into the air* and received by the coil of the PU.
Then MASSIVELY amplified by all the processing crap that was hanging off it.
Any single coil PU will do the same thing and twin coil types ( ie
humbuckers ) will not.

When Phil comes on like that you must be prepared to handle the risk that
he is right, he admittedly often is.

** And YOU never are - fuckhead.

Post by Peter Larsen
Whenever you have RFI

** There is no Radio Frequency involved - fuckwit !!!
The term is EMI = Electro Magnetic Interference !!!!

Post by Peter Larsen
there is something mains-driven that emits RFI then it is makes sense to
me that the RFI should also be visible overlaid the mains voltage.

** Why do you keep using the WRONG term ??

Post by Peter Larsen
That does NOT PREVENT IT FROM ENTERING PICKUPS DIRECTLY PHIL,

** Guitar pickup do not respond to RFI - fuckwit.
Guitar pickups do not respond to mains borne EMI either.
FYI " mains borne interference " = interference carried into equipment
by mains cabling.
BTW fluoro dimming is NOT done at audio frequencies.
... Phil

Here's the answer.

Some Pommy fuckwit has been carrying out Geophys surveys in the vicinity,
probably to build a new Underground system for the Olympics or something.

http://pubs.usgs.gov/of/2000/of00-360/



Gareth.

[Lord Valve]

Post by Phil Allison
** Guitar pickup do not respond to RFI - fuckwit.

Put one next to a cellphone and see what happens. ;-)


Lord Valve
ASD-fucked autistic pig-ignorant septic criminal fuckwit (etc.)

[Denny Strauser]

Post by Phil Allison
** Guitar pickup do not respond to RFI - fuckwit.
Guitar pickups do not respond to mains borne EMI either.

So what guitar pickups respond to? Is it not the Electro-Magnetic
influence between the strings & pickups? And what is the difference
between EMI & RFI? Frequency?

- D

[Denny Strauser]

Post by Phil Allison
Guitar pickups do not respond to mains borne EMI either.

Probably true, but ...
I've heard many electric guitars go into EMI feedback through their own
amps.

[Lord Valve]

Post by Denny Strauser

Post by Phil Allison
Guitar pickups do not respond to mains borne EMI either.

Probably true, but ...
I've heard many electric guitars go into EMI feedback through their own
amps.

No, I don't think you have.

Guitar feedback is an acoustic phenomenon; you
can kill it by removing your finger from the string in
question, or touching the string with another finger.

Lord Valve
...who may know a thing or two about guitar amps...

[Phil Allison]

"Lord Valve"

Post by Lord Valve

Post by Denny Strauser

Phil Allison
Guitar pickups do not respond to mains borne EMI either.

I've heard many electric guitars go into EMI feedback through their own
amps.

No, I don't think you have.

** He possibly has actually.

Post by Lord Valve
Guitar feedback is an acoustic phenomenon;

** But pickup feedback may be purely electrical.

If the pickup is close to the speaker/s and the amp has lots of gain at high
audio or supersonic frequencies - electrical positive feedback can occur.
This most likely with single coil, unshielded type pickups.

The player may hear a very high pitched tone or a humming noise from the
speaker/s - both of which
stop if the guitar is moved away.

Grounding the frames of the speakers usually eliminates the oscillation -
which indicates the feedback is due to stray capacitance.

Also, pickups can be microphonic and generate loud feedback squeals at a few
kHz all on their own.


... Phil

[Lord Valve]

Post by Phil Allison
"Lord Valve"

Post by Lord Valve

Post by Denny Strauser

Phil Allison
Guitar pickups do not respond to mains borne EMI either.

I've heard many electric guitars go into EMI feedback through their own
amps.

No, I don't think you have.

** He possibly has actually.

Post by Lord Valve
Guitar feedback is an acoustic phenomenon;

** But pickup feedback may be purely electrical.
If the pickup is close to the speaker/s and the amp has lots of gain at high
audio or supersonic frequencies - electrical positive feedback can occur.
This most likely with single coil, unshielded type pickups.
The player may hear a very high pitched tone or a humming noise from the
speaker/s - both of which
stop if the guitar is moved away.
Grounding the frames of the speakers usually eliminates the oscillation -
which indicates the feedback is due to stray capacitance.
Also, pickups can be microphonic and generate loud feedback squeals at a few
kHz all on their own.
... Phil

I'll allow it, but file it under *extremely* unlikely.

LV

[Phil Allison]

"Lord Valve"

Post by Lord Valve

Post by Phil Allison
"Lord Valve"

Post by Lord Valve

Post by Denny Strauser

Phil Allison
Guitar pickups do not respond to mains borne EMI either.

I've heard many electric guitars go into EMI feedback through their own
amps.

No, I don't think you have.

** He possibly has actually.

Post by Lord Valve
Guitar feedback is an acoustic phenomenon;

** But pickup feedback may be purely electrical.
If the pickup is close to the speaker/s and the amp has lots of gain at high
audio or supersonic frequencies - electrical positive feedback can occur.
This most likely with single coil, unshielded type pickups.
The player may hear a very high pitched tone or a humming noise from the
speaker/s - both of which
stop if the guitar is moved away.
Grounding the frames of the speakers usually eliminates the oscillation -
which indicates the feedback is due to stray capacitance.
Also, pickups can be microphonic and generate loud feedback squeals at a few
kHz all on their own.

I'll allow it, but file it under *extremely* unlikely.

** It's pretty common actually.

Stand close to a Marshall plus quad box stack with a Strat and everything
cranked and it's guaranteed.

It is one of the common causes of arced across tube bases and sockets -
plus fried OP trannys.

Players do not realise what is happening ( except for a loss of power and
tone ) until they see red glowing tubes or HT /AC fuses blow.



... Phil

[Denny Strauser]

Post by Lord Valve

Post by Denny Strauser

Post by Phil Allison
Guitar pickups do not respond to mains borne EMI either.

Probably true, but ...
I've heard many electric guitars go into EMI feedback through their own
amps.

No, I don't think you have.
Guitar feedback is an acoustic phenomenon; you
can kill it by removing your finger from the string in
question, or touching the string with another finger.
Lord Valve
...who may know a thing or two about guitar amps...

You might be right. I've heard guitars go "microphonic" with the strings
dampened. I've been told that this squeal is caused by the
electromagnetic field interaction between the speaker & pickups. It
happens when the amp is turned up loud, the guitar has single coil
pickups & is too close to the amp. It is clearly not acoustic feedback,
if the strings are dampened. What is the cause, if it is not acoustic
feedback. And if the guitar is not being played, it does not fit the
definition of microphonic. So, what is this phenomenon?

- Denny

[Denny Strauser]

Post by Denny Strauser
You might be right. I've heard guitars go "microphonic" with the strings
dampened. I've been told that this squeal is caused by the
electromagnetic field interaction between the speaker & pickups. It
happens when the amp is turned up loud, the guitar has single coil
pickups & is too close to the amp. It is clearly not acoustic feedback,
if the strings are dampened. What is the cause, if it is not acoustic
feedback. And if the guitar is not being played, it does not fit the
definition of microphonic. So, what is this phenomenon?

I think Phil answered my question.

- Denny

[Denny Strauser]

Post by Peter Larsen
When Phil comes on like that you must be prepared to handle the risk that he
is right, he admittedly often is.
Whenever you have RFI then it can be helpful to bring a scope. And it is
possibly a good idea to go there at 11 am and check things. If there is
something mains-driven that emits RFI then it is makes sense to me that the
RFI should also be visible overlaid the mains voltage. That does NOT PREVENT
IT FROM ENTERING PICKUPS DIRECTLY PHIL, but it make it simpler to pinpoint
it. And the interference sounds just like the triac noise that entered my
ReVox A77HS from a light desk 3 feet from it except that the frequency is
higher. THAT is my reason for posting the asumption that it correlates with
something that chops mains voltage, dimmers for fluorescents in my
understanding - YO PHIL POMMYLOT, THIS IS WHERE YOUR KNOWHOW WOULD BE WELL
APPLIED - do that.

Post by Gareth Magennis
It is not beyond the realms of possibility, though, that more than one
factor is contributing to the symptoms experienced.
This interference has not happened before, the railway has been there
for quite some time now - the addition of some "wavechopping"
equipment onto the mains supply could in some way be contributing to
the effect observed (e.g. the guitarists FX units power supply may
now be contaminated with all kinds of shite, which may interact with
or modulate a different kind of shite being picked up by the single
coil pickups).

Troubleshooting question 1: did it ever work
Troubleshooting question 2: what changed
Go get Pease's book on troubleshooting analog circuits, nobody here should
be without it!

I'll read up on it ...

Post by Peter Larsen
Kind regards - also to Phil
Peter Larsen

Peter is always so polite, I sometimes think he must be Canadian. But
never Australian ...

- Denny

[Peter Larsen]

Post by Gareth Magennis
Here's a clip of the Interference - almost a perfect "E".
http://kiwi6.com/file/u5i1i5x53g

Put a scope on the mains power and see how it looks!

Post by Gareth Magennis
Gareth

Kind regards

Peter Larsen

[Phil Allison]

"Gareth Magennis"

Post by Gareth Magennis
http://kiwi6.com/file/u5i1i5x53g

** This is a nasty site

- it sends an exe file to your PC that changes your home page and generates
annoying pop ups.



... Phil

[Gareth Magennis]

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
http://kiwi6.com/file/u5i1i5x53g

** This is a nasty site
- it sends an exe file to your PC that changes your home page and
generates annoying pop ups.
... Phil

Apologies to all in that case, I don't usually post mp3's anywhere.

Any better suggestions will be duly noted.


Cheers,

Gareth.

[Peter Larsen]

Post by Phil Allison
"Gareth Magennis"

Post by Gareth Magennis
http://kiwi6.com/file/u5i1i5x53g

** This is a nasty site
- it sends an exe file to your PC that changes your home page and
generates annoying pop ups.

Not to me, xp home, ie8 + microsoft security essentials.

Post by Phil Allison
... Phil

Kind regards

Peter Larsen