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#1
Posted to rec.audio.tech,rec.audio.pro
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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. |
#2
Posted to rec.audio.tech,rec.audio.pro
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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! |
#3
Posted to rec.audio.tech,rec.audio.pro
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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." |
#4
Posted to rec.audio.tech,rec.audio.pro
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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? |
#5
Posted to rec.audio.tech,rec.audio.pro
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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." |
#6
Posted to rec.audio.tech,rec.audio.pro
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RFI from my Event tr8 monitors
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#7
Posted to rec.audio.tech,rec.audio.pro
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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 |
#8
Posted to rec.audio.tech,rec.audio.pro
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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 |
#9
Posted to rec.audio.tech,rec.audio.pro
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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." |
#10
Posted to rec.audio.tech,rec.audio.pro
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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 |
#11
Posted to rec.audio.tech,rec.audio.pro
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RFI from my Event tr8 monitors
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#12
Posted to rec.audio.tech,rec.audio.pro
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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. |
#13
Posted to rec.audio.tech,rec.audio.pro
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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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