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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors

The tweeter of my powered event tr8 monitors are picking up radio. its
very quiet but in silence its annoying.

I took one of my tr8's and moved it to different rooms and plugged in
the power with ground line connected and not connected, also with no
audio cable connected. I always got the same annoying radio signal
coming out of the tweeter, with the radio signal being the same volume
regardless on what the gain of the powered monitor was set to, since
the tr8's have a knob thats from -20db to 0db. The "shhhhhh" sound
which all speakers have would change volumes as the db knob turns, but
the RFI volume would not. whether the monitor was grounded or not, I
received the same results.. RFI!

I took the other other tr8 monitor since I have a pair and did the same
test and received the same results. I never opened these monitors. they
have never been dropped. I've had them for a little over 2 1/2 years.
maybe its just my ears but sometimes its louder than depending on
location. I really dont know what it is, and what I can do to prevent
it. I use an LCD monitor so I know its not a crt problem, and the only
cable connected to the monitors was the power cable. all the power
cables from my preamp to my computer to my monitors to my dual
flatpanel lcds are same basically. if you have any idea feel free to
post it.

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Dave Platt Dave Platt is offline
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Default RFI from my Event tr8 monitors

In article om,
wrote:

The tweeter of my powered event tr8 monitors are picking up radio. its
very quiet but in silence its annoying.


Technically, this is more properly called "undesired reception" - that
is, a device which should not be sensitive to RF, is
receiving/detecting RF.

I took one of my tr8's and moved it to different rooms and plugged in
the power with ground line connected and not connected, also with no
audio cable connected. I always got the same annoying radio signal
coming out of the tweeter, with the radio signal being the same volume
regardless on what the gain of the powered monitor was set to, since
the tr8's have a knob thats from -20db to 0db. The "shhhhhh" sound
which all speakers have would change volumes as the db knob turns, but
the RFI volume would not. whether the monitor was grounded or not, I
received the same results.. RFI!


Good test procedure! You've eliminated a lot of possible culprits.

I took the other other tr8 monitor since I have a pair and did the same
test and received the same results. I never opened these monitors. they
have never been dropped. I've had them for a little over 2 1/2 years.
maybe its just my ears but sometimes its louder than depending on
location. I really dont know what it is, and what I can do to prevent
it.


Your tests strongly suggest that the RF is being "detected" (converted
back into audio) in a relatively late stage in the amplification
circuitry... after the volume control. Odds are very good that it's
coming in through the power cable... possibly by direct pickup by that
one cable, or possibly by conduction from the house wiring.

The first thing I would suggest is adding a ferrite "choke" to the
power cable. These come in a variety of sizes and shapes and types...
toroids (donuts), cylinders, and rods.

There's probably already a ferrite RF choke on each of your monitor
cables (look for a cylindrical swelling of the cable, near the monitor
and/or near the plug which connects to the computer.

Probably the easiest thing for you to find, and try, is a "snap-on"
cylindrical ferrite bead. For examples, see

http://www.allelectronics.com/cgi-bi.../Ferrites.html

I suspect that Radio Shack may still carry beads of this sort (at a
rather higher price), although their online catalog / product index is
so useless I can't find 'em.

The right way to use one of these beads, in your application, is to
snap the bead around the power cord as close as possible to the
speaker cabinet. If you can, loop the cord around one half of the
bead (i.e. through the center and then around the outside) several
times before you snap it closed - the impedance of the resulting choke
goes up roughly proportional to the square of the number of turns, and
this will improve the RF blocking.

Since your speakers are known to be sensitive to RF pickup, I'd
suggest buying four beads - one for each monitor's power cord, and
another for the audio interconnect cable you plug into the monitor.

It's possible to do more extensive internal modifications to an
amplifier to reduce its RF sensitivity, but I think the chances are
good that snubbing the power and audio cables with ferrite beads will
eliminate the problem.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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Scott Dorsey Scott Dorsey is offline
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Default RFI from my Event tr8 monitors

wrote:

I took one of my tr8's and moved it to different rooms and plugged in
the power with ground line connected and not connected, also with no
audio cable connected. I always got the same annoying radio signal
coming out of the tweeter, with the radio signal being the same volume
regardless on what the gain of the powered monitor was set to, since
the tr8's have a knob thats from -20db to 0db. The "shhhhhh" sound
which all speakers have would change volumes as the db knob turns, but
the RFI volume would not. whether the monitor was grounded or not, I
received the same results.. RFI!


If you unplug it from the wall, it should run for several seconds before
shutting down. In that time, do you hear the radio?

Can you identify the station? Is the transmitter site nearby?

I took the other other tr8 monitor since I have a pair and did the same
test and received the same results. I never opened these monitors. they
have never been dropped. I've had them for a little over 2 1/2 years.
maybe its just my ears but sometimes its louder than depending on
location. I really dont know what it is, and what I can do to prevent
it. I use an LCD monitor so I know its not a crt problem, and the only
cable connected to the monitors was the power cable. all the power
cables from my preamp to my computer to my monitors to my dual
flatpanel lcds are same basically. if you have any idea feel free to
post it.


A lot of the inexpensive gear these days is not heavily tested for radio
interference issues, and some of it has had some power supply corners cut.
As a result, it may have to be modified if you are working in a high RF
environment. Can you identify the station?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors


Scott Dorsey wrote:

If you unplug it from the wall, it should run for several seconds before
shutting down. In that time, do you hear the radio?


thats an accelent idea. After doing what you just described the radio
noise went away and I could hear pure shhhhhhh for a quater of a
second


Can you identify the station? Is the transmitter site nearby?


Yes I can identify the radio station. its 99x in atlanta; its FM. its a
little over 5 miles away from the address given on their website. I
dont think the actual transmitter is there, but I have no idea.

I need to buy better power cables?

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Scott Dorsey Scott Dorsey is offline
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Default RFI from my Event tr8 monitors

wrote:
Scott Dorsey wrote:

If you unplug it from the wall, it should run for several seconds before
shutting down. In that time, do you hear the radio?


thats an accelent idea. After doing what you just described the radio
noise went away and I could hear pure shhhhhhh for a quater of a
second


So it's coming in on the power line. Try a big ferrite on the power line.

More likely installing a Corcom EMI filter inside the box is a permanent
solution, but you will inavariably have it coming in on the audio lines
as well once you fix that. But it's the first step.

Can you identify the station? Is the transmitter site nearby?


Yes I can identify the radio station. its 99x in atlanta; its FM. its a
little over 5 miles away from the address given on their website. I
dont think the actual transmitter is there, but I have no idea.


You SURE it's FM and not AM?
Give me the call letters and I'll look it up on the FCC database and
tell you where the transmitter is, or if they have an AM simulcast.

Note that downtown Atlanta used to be the #1 worst RF area in the country,
and the section between the CNN building and the WTBS building was known
as "intermod alley."

I need to buy better power cables?


No, that will do nothing. You need to fix the problem inside the box.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."


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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors

I'm pretty sure the radio station is only fm

http://en.wikipedia.org/wiki/WNNX-FM


before I moved my speakers all over the house I had them plugged into a
UPS

http://www.newegg.com/Product/Produc...82E16842102044

took the UPS off ground for a minute just to see if it made a
difference and it didnt.

is there anyway to shield using tinfoil or something? just to see if it
does anything. I put a radio by the speakers to see if it would do
anything and it didnt. at the end of the power cords, the thick plastic
that the 3 prongs are sticking out of seem to cover some of the wire as
if a little ring over the wire was encased right before the 3 prongs.
maybe thats for EMI reduction?

thanks for the help

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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors

I'm pretty sure the radio station is only fm

http://en.wikipedia.org/wiki/WNNX-FM


before I moved my speakers all over the house I had them plugged into a

UPS


http://www.newegg.com/Product/Produc...82E16842102044


took the UPS off ground for a minute just to see if it made a
difference and it didnt.


is there anyway to shield using tinfoil or something? just to see if it

does anything. I put a radio by the speakers to see if it would do
anything and it didnt. at the end of the power cords, the thick plastic

that the 3 prongs are sticking out of seem to cover some of the wire as

if a little ring over the wire was encased right before the 3 prongs.
maybe thats for EMI reduction?

as far as emi coming through audio cables, I had a bunch of noise
coming from a ground loop. my computer thats on ground to my soundcard
thats off ground to my speakers thats on ground with an audio cable
which has a ground line between the soundcard and the speakers. so you
can pretty much see the loop. but getting balanced cables erased that
problem totally. I wish there were balanced power cables


thanks for the help

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Scott Dorsey Scott Dorsey is offline
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Default RFI from my Event tr8 monitors

wrote:

is there anyway to shield using tinfoil or something? just to see if it
does anything. I put a radio by the speakers to see if it would do
anything and it didnt. at the end of the power cords, the thick plastic
that the 3 prongs are sticking out of seem to cover some of the wire as
if a little ring over the wire was encased right before the 3 prongs.
maybe thats for EMI reduction?


The speakers themselves should (if they are well-designed) have a Faraday
shield inside them to keep RF from getting in directly. This is a more
elegant version of the tinfoil wrapper. But, all of the inputs (both power
and signal) into the amplifier stage can act as antennae, and bring RF into
the box. So it needs _both_ a Faraday shield, and filters on all of the
inputs to prevent the RF from getting picked up by a wire and then
re-radiated inside.

Try the ferrite choke, as close as possible to the speaker. If that does
not work, you're going to need to do actual modification to install real
filtration inside the box.

This is the difference between consumer and pro gear.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors

yeah I figured that. its not like its audible unless its absolutely
quite or your ear is right next to the tweeter. but sometimes when I'm
making music at my desk at night its annoying when I hear this radio.
thanks for the help



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Mark Mark is offline
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Default RFI from my Event tr8 monitors


wrote:
I'm pretty sure the radio station is only fm

http://en.wikipedia.org/wiki/WNNX-FM




are you near the transmitter... it will be a BIG tower,.....exactly how
near are you?

If it is FM via the power corad, those ferrite blocks should
help,,,even coiling the power cord may help...

Mark

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Chip Borton Chip Borton is offline
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Default RFI from my Event tr8 monitors

Call Event tech support.
There is a modification they can do to the boards that will
prevent them from picking up interference.
I think its just adding a better filter cap to the power
supply section.


wrote in message
ps.com...
The tweeter of my powered event tr8 monitors are picking up radio. its
very quiet but in silence its annoying.



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[email protected] SamiSWilf@yahoo.com is offline
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Default RFI from my Event tr8 monitors

just thought to paste this for anyone else having the same problem

In early runs of the TR series monitors we had some problems with RF
interference in just a few areas of the country. Atlanta was one. The
problem has been fixed as of early 2004. We would be glad to take your
monitors back and apply this fix at your convenience. No charge of
course. Contact Q (yes his name is Q, don't ask) at 805 566-7777 ext.
274 or

Thanks for buying Event. Happy mixing!

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