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#1
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Ribbon Mic picking up Radio Frequency Interference
I have a ribbon microphone that is picking up AM radio. I had no idea
what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. The problem is not constant, it comes and goes. I've tried the mic with different preamps and I get the same problem with both. I've also tried different microphones. Only the ribbon mic picks up this RMI squeal. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? Is this problem due to noisy power lines and will getting a power conditioner eliminate it do you think? I had my equipment in the same room as the mic. I moved it out of the room and into the hall to test and the problem remains. Replaced all fluorescent bulbs with regular incandescent ones. There is a dimmer in the house, but it's located down the hall and far away and is turned off. Nothing is powered on in the same room as the mic now and the squeal is still there. I've turned off all radios in the house as well. Unplugged a wireless router. None of this helps, which makes me think it's the power. |
#2
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Does the interference change when you move the mic cable around?
Peace, Paul |
#3
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote: I have a ribbon microphone that is picking up AM radio. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? I think you mean "I'm just wondering what is demodulating the interference" and the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if it's there, the trick is not to demodulate it. What's the mic ? What's your preamp / mixer / interface ? Graham |
#4
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
"Truth" wrote in message ups.com... I have a ribbon microphone that is picking up AM radio. I don't think so. What you have is a mic that is picking up RF and a mic preamp or something else that is demodulating the RF and presenting the modulation of the RF as audio. I had no idea what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. The squeal might be a hetrodyne between two different RF sources. Hetrodynes are due to nonlinearity. The nonlinearity is probably due to some active component being driven outside its linear range. But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. Seems consistent with the other things that you've said so far. The problem is not constant, it comes and goes. Moving mics and cables around can cause these sorts of changes. I've tried the mic with different preamps and I get the same problem with both. Either the two preamps share the same sensitivity to RF, or the problem is elsewhere. I've also tried different microphones. Only the ribbon mic picks up this RMI squeal. One major variable is that ribbon mics usually demand that a lot more gain be used to amplify them. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? A corroded connection in the mic itself could be providing the necessary nonlinearity. Or, your mic preamps might be doing just fine all by themselves, but are outputting too much RF for some downstream component to handle linearly. Is this problem due to noisy power lines and will getting a power conditioner eliminate it do you think? No. I suspect that your mic cables are acting like antennas. I had my equipment in the same room as the mic. I moved it out of the room and into the hall to test and the problem remains. Replaced all fluorescent bulbs with regular incandescent ones. There is a dimmer in the house, but it's located down the hall and far away and is turned off. Dimmer noise is generally overlaid with the power line frequency. So, its more like a buzz than a squeal or a radio station program. Nothing is powered on in the same room as the mic now and the squeal is still there. I've turned off all radios in the house as well. Unplugged a wireless router. None of this helps, which makes me think it's the power. The RF is most likely in the space in and around your house. Something as simple as a low value ceramic capacitor across the mics terminals could make a difference. I've found that mic preamps vary tremendously in how well-equipped they are to reject RF. Some have multiple-section LC filters (good) and some have nothing in particular or maybe just a capacitor across the input terminals (not so good). I think that the best mic preamp I have in terms of RF rejection is my SX 202. Frankly, for whatever reason, I've mostly used the SX 202 in my remote recording sessions, some of which have been in the high-RF parts of my city. I don't know how many problems I've never experienced because of my choice of equipment. I don't use ribbon mics at all, so I don't know what would happen with a more difficult microphone than the common kinds of condensor mics that I prefer. |
#5
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Arny Krueger wrote: I've found that mic preamps vary tremendously in how well-equipped they are to reject RF. Some have multiple-section LC filters (good) and some have nothing in particular or maybe just a capacitor across the input terminals (not so good). And different designs vary hugely as to their susceptibilty too. Very few 'consumer' or pro-sumer mic pre designs employ much in the way of any series L (inductance) at the front end. Graham |
#6
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. Are you saying you can hear the same squeal on the AM radio when you listen to the station? Why is there a squeal on that station? Is the station located near you...how far, how much power is it Tx? What frequency is the AM station? What frequency is the squeal? Is you audio equipment all analog or is the signal digitized at some point? With what sampling rate? The squeal may be an aliasing issue. Mark |
#7
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote:
I have a ribbon microphone that is picking up AM radio. I had no idea what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. What kind if microphone? What kind of special cables? What kind of preamp? Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? Is this problem due to noisy power lines and will getting a power conditioner eliminate it do you think? Something has turned into a big antenna and is picking up RF... then something else is rectifying it. It's very common for this to be a cable issue combined with a preamp issue. Google "pin 1 problem" for one of the more common sources. Fixing either the pickup or the rectification will fix the problem, but it would be wise to deal with both. Can you hear the demodulated voice of the AM station? I had my equipment in the same room as the mic. I moved it out of the room and into the hall to test and the problem remains. Replaced all fluorescent bulbs with regular incandescent ones. There is a dimmer in the house, but it's located down the hall and far away and is turned off. Nothing is powered on in the same room as the mic now and the squeal is still there. I've turned off all radios in the house as well. Unplugged a wireless router. None of this helps, which makes me think it's the power. What IS this equipment? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#8
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Arny Krueger wrote: [cut] I've found that mic preamps vary tremendously in how well-equipped they are to reject RF. Some have multiple-section LC filters (good) and some have nothing in particular or maybe just a capacitor across the input terminals (not so good). [cut] Does a preamp with a transformer balanced input do a better job rejecting RF? Andy |
#9
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
AndyP wrote: Arny Krueger wrote: I've found that mic preamps vary tremendously in how well-equipped they are to reject RF. Some have multiple-section LC filters (good) and some have nothing in particular or maybe just a capacitor across the input terminals (not so good). Does a preamp with a transformer balanced input do a better job rejecting RF? Generally it does. I expect incompetent product design could perhaps mess that up too but transformer inputs do indeed normally perform very well in this respect. Graham |
#10
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
In article , AndyP wrote:
Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#11
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Scott Dorsey wrote: AndyP wrote: Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? He said it was an AM station. AM is also readily demodulated by any diode-like behaviour. Graham |
#12
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
Eeyore wrote:
Scott Dorsey wrote: AndyP wrote: Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? He said it was an AM station. Right, but he said he was hearing a whistle. AM is also readily demodulated by any diode-like behaviour. Yes, but then you hear voices. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#13
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Ribbon Mic picking up Radio Frequency Interference
"Scott Dorsey" wrote in message ... Eeyore wrote: Scott Dorsey wrote: AndyP wrote: Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? He said it was an AM station. Right, but he said he was hearing a whistle. Probably a separate issue that coincidentally shows up. |
#14
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around? Peace, Paul Thanks for all your replies and help, I appreciate it. I haven't tried that yet while the problem is occurring. I will do that and see what happens next time. Up to this point, I have left the cable in the same spot unmoved. Sometimes I hear absolutely no squeal/whistle and at other times the noise is unbearable, all the while I have not touched the cables. |
#15
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote:
Thanks for all your replies and help, I appreciate it. I haven't tried that yet while the problem is occurring. I will do that and see what happens next time. Up to this point, I have left the cable in the same spot unmoved. Sometimes I hear absolutely no squeal/whistle and at other times the noise is unbearable, all the while I have not touched the cables. What model microphone, preamp, and cable are we talking about here? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#16
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 7:15 am, Eeyore
wrote: Truth wrote: I have a ribbon microphone that is picking up AM radio. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? I think you mean "I'm just wondering what is demodulating the interference" and the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if it's there, the trick is not to demodulate it. What's the mic ? What's your preamp / mixer / interface ? Graham Interesting. Could the problem perhaps originate in the power, get transferred and made worse on the way to the computer? My chain: House Power Ribbon Mic's Power Box Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI Lynx Two C Sound Card |
#17
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Ribbon Mic picking up Radio Frequency Interference
"Truth" wrote ...
I have a ribbon microphone that is picking up AM radio. I had no idea what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. As you know by now, throwing out generic anecdotes with no details won't get you very far. But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. The problem is not constant, it comes and goes. I've tried the mic with different preamps and I get the same problem with both. I've also tried different microphones. Only the ribbon mic picks up this RMI squeal. You aren't supposed to hear ANY "squeal" when you listen to radio (else nobody would listen). I would track down why you are hearing this "squeal" even on a standalone radio (independent of your problematic sound system). Call the radio station and complain that you hear a squeal when you try to listen to them. Could even be some kind of pirate radio station one of your neighbors is transmitting, etc. |
#18
Posted to rec.audio.pro
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 7:48 am, "Arny Krueger" wrote:
"Truth" wrote in message ups.com... I have a ribbon microphone that is picking up AM radio. I don't think so. What you have is a mic that is picking up RF and a mic preamp or something else that is demodulating the RF and presenting the modulation of the RF as audio. I had no idea what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. The squeal might be a hetrodyne between two different RF sources. Hetrodynes are due to nonlinearity. The nonlinearity is probably due to some active component being driven outside its linear range. But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. Seems consistent with the other things that you've said so far. The problem is not constant, it comes and goes. Moving mics and cables around can cause these sorts of changes. I've tried the mic with different preamps and I get the same problem with both. Either the two preamps share the same sensitivity to RF, or the problem is elsewhere. I've also tried different microphones. Only the ribbon mic picks up this RMI squeal. One major variable is that ribbon mics usually demand that a lot more gain be used to amplify them. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? A corroded connection in the mic itself could be providing the necessary nonlinearity. Or, your mic preamps might be doing just fine all by themselves, but are outputting too much RF for some downstream component to handle linearly. Is this problem due to noisy power lines and will getting a power conditioner eliminate it do you think? No. I suspect that your mic cables are acting like antennas. I had my equipment in the same room as the mic. I moved it out of the room and into the hall to test and the problem remains. Replaced all fluorescent bulbs with regular incandescent ones. There is a dimmer in the house, but it's located down the hall and far away and is turned off. Dimmer noise is generally overlaid with the power line frequency. So, its more like a buzz than a squeal or a radio station program. Nothing is powered on in the same room as the mic now and the squeal is still there. I've turned off all radios in the house as well. Unplugged a wireless router. None of this helps, which makes me think it's the power. The RF is most likely in the space in and around your house. Something as simple as a low value ceramic capacitor across the mics terminals could make a difference. I've found that mic preamps vary tremendously in how well-equipped they are to reject RF. Some have multiple-section LC filters (good) and some have nothing in particular or maybe just a capacitor across the input terminals (not so good). I think that the best mic preamp I have in terms of RF rejection is my SX 202. Frankly, for whatever reason, I've mostly used the SX 202 in my remote recording sessions, some of which have been in the high-RF parts of my city. I don't know how many problems I've never experienced because of my choice of equipment. I don't use ribbon mics at all, so I don't know what would happen with a more difficult microphone than the common kinds of condensor mics that I prefer. These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. If that is the case, then what can be done about it? Could the problem originate in the power source and made worse by long cable runs? I have to get in contact with them again and see what they say as well. Perhaps getting shorter ribbon mic cables will help, since you say the problem could be the ribbon mic cables acting as antennas. |
#19
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Ribbon Mic picking up Radio Frequency Interference
Scott Dorsey wrote: Eeyore wrote: Scott Dorsey wrote: AndyP wrote: Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? He said it was an AM station. Right, but he said he was hearing a whistle. AM is also readily demodulated by any diode-like behaviour. Yes, but then you hear voices. You got me there. Joke ? Graham |
#20
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote: "Paul Stamler" wrote: Does the interference change when you move the mic cable around? Thanks for all your replies and help, I appreciate it. I haven't tried that yet while the problem is occurring. I will do that and see what happens next time. Up to this point, I have left the cable in the same spot unmoved. Sometimes I hear absolutely no squeal/whistle and at other times the noise is unbearable, all the while I have not touched the cables. Something that I don't think we've yet touched on is that there may be some instability (oscillation) at very high frequencies in your equipment and it's mixing with the RF. That could cause a 'scream'. Graham |
#21
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 8:45 am, Mark wrote:
But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. Are you saying you can hear the same squeal on the AM radio when you listen to the station? Why is there a squeal on that station? Is the station located near you...how far, how much power is it Tx? What frequency is the AM station? What frequency is the squeal? Is you audio equipment all analog or is the signal digitized at some point? With what sampling rate? The squeal may be an aliasing issue. Mark 790 AM I get lots of squeal/whistle when I tune into that station on a radio. I'm recording at 96K, 32bits. In reply to Paul Stamler I listed my recording chain. Mostly digital. The Pendulum is a tube preamp. When used with the ribbons I sometimes get a squeal. The Weiss ADC2 can send out analog and digital. I'm sending out a DO to the Lynx Two's DI. |
#22
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Ribbon Mic picking up Radio Frequency Interference
"Eeyore" wrote ...
Something that I don't think we've yet touched on is that there may be some instability (oscillation) at very high frequencies in your equipment and it's mixing with the RF. That could cause a 'scream'. If he hears the same "squeal" in an independent radio receiver, it could be an indication of something wierd happening in his RF neighborhood. His audio recording equipment could be operating "nominally" and we are barking up the wrong tree. |
#23
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:02 pm, "Richard Crowley" wrote:
"Truth" wrote ... I have a ribbon microphone that is picking up AM radio. I had no idea what it was until today. It's usually a squeal and I don't hear the voice or music. So I was guessing and trying different things all to no avail. I was turning off equipment, moving it far away from the mics, removing any fluorescent lights, etc. Problem remained. I even got some special power cords for the mic power supplies. Still, the squeal is there. As you know by now, throwing out generic anecdotes with no details won't get you very far. But today, in addition to the squeal like you're getting a bad radio signal, I could hear the radio content as well which made it clear what the problem was. I turned on the radio downstairs and tuned it to AM. I found the station the mic was picking up in my recording and it was the same type of squeal, so it seems this is the problem. The problem is not constant, it comes and goes. I've tried the mic with different preamps and I get the same problem with both. I've also tried different microphones. Only the ribbon mic picks up this RMI squeal. You aren't supposed to hear ANY "squeal" when you listen to radio (else nobody would listen). I would track down why you are hearing this "squeal" even on a standalone radio (independent of your problematic sound system). Call the radio station and complain that you hear a squeal when you try to listen to them. Could even be some kind of pirate radio station one of your neighbors is transmitting, etc. It's a commercial station. 790 AM. I think the same station as some talk shows. When I could hear the station it was a Christian Radio Program. |
#24
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 11:52 am, (Scott Dorsey) wrote:
Truth wrote: Thanks for all your replies and help, I appreciate it. I haven't tried that yet while the problem is occurring. I will do that and see what happens next time. Up to this point, I have left the cable in the same spot unmoved. Sometimes I hear absolutely no squeal/whistle and at other times the noise is unbearable, all the while I have not touched the cables. What model microphone, preamp, and cable are we talking about here? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." My chain: House Power Ribbon Mic's Power Box Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI Lynx Two C Sound Card |
#25
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 11:17 am, (Scott Dorsey) wrote:
In article , AndyP wrote: Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. There are some poorly-designed transformer inputs out there too, though. What kind of preamp, microphone, and cable are we dealing with here? And what makes you think it's AM? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." My chain: House Power Ribbon Mic's Power Box Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI Lynx Two C Sound Card |
#26
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 9:34 am, "AndyP" wrote:
Does a preamp with a transformer balanced input do a better job rejecting RF? Almost always. But we haven't established yet that Truth has an RFI problem, or if RFI is hs only problem. The radio station is definitely suspicious but the description of the noise as a squeal that's sometimes unbearable suggests feedback. All of his gear is good quality stuff so I'm suspecting either cockpit trouble or something broken. I wonder what he hears when he substitutes a different mic for the Royer, or better yet, substitutes a "dummy mic" - an XLR plug with a 150 ohm resistor connected between pins 2 and 3. |
#27
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote: Eeyore wrote: Truth wrote: I have a ribbon microphone that is picking up AM radio. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? I think you mean "I'm just wondering what is demodulating the interference" and the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if it's there, the trick is not to demodulate it. What's the mic ? What's your preamp / mixer / interface ? Graham Interesting. Could the problem perhaps originate in the power, get transferred and made worse on the way to the computer? Not really. My chain: House Power Ribbon Mic's Power Box Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some strange 'head amplifier'. I wouln't mind betting there's your problem. Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) What do you mean by non-standard ? Alarm bells are ringing already. 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI A DH Labs DI ? I can't find anything by googling. Is it active or passive ? Graham |
#28
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote: I even got some special power cords for the mic power supplies. Why ? What did you expect it to do ? AC power doesn't need 'special cords'. They're only for gullible 'audiophools'. Graham |
#29
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Ribbon Mic picking up Radio Frequency Interference
"Truth" wrote ...
It's a commercial station. 790 AM. I think the same station as some talk shows. When I could hear the station it was a Christian Radio Program. If you are hearing the same "squeal", interference, etc. on this radio receiver, why do you suspect anything is wrong with your audio equipment? Since we have no clue where you are "790 AM" means nothing to us. There are 100 radio stations on that freuency just in North America. |
#30
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:20 pm, Eeyore
wrote: Truth wrote: Eeyore wrote: Truth wrote: I have a ribbon microphone that is picking up AM radio. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? I think you mean "I'm just wondering what is demodulating the interference" and the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if it's there, the trick is not to demodulate it. What's the mic ? What's your preamp / mixer / interface ? Graham Interesting. Could the problem perhaps originate in the power, get transferred and made worse on the way to the computer? Not really. My chain: House Power Ribbon Mic's Power Box Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some strange 'head amplifier'. I wouln't mind betting there's your problem. Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) What do you mean by non-standard ? Alarm bells are ringing already. 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI A DH Labs DI ? I can't find anything by googling. Is it active or passive ? Graham Sorry, that wasn't clear. DH labs 12 feet 110 Ohm XLR used as the connection between the preamps and the sound card. Two used for an analog connection between the Pendulum and the Lynx Two C, one used for the connection between the Weiss ADC2 Digital Output to the sound card's digital input. |
#31
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Ribbon Mic picking up Radio Frequency Interference
Truth wrote: These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer Why ? Same problem or a different one ? and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. They're talking crap. It probably means they know their design is defective. If that is the case, then what can be done about it? Reject them and buy something that works properly ? Could the problem originate in the power source If it was just a 'power source' it would be unlikely but it seems it contains some active electronics (i.e it has gain). Certainly that electronics could be defective. You sound a bit vague about understanding what you've bought. and made worse by long cable runs? Not really. I have to get in contact with them again and see what they say as well. Perhaps getting shorter ribbon mic cables will help, since you say the problem could be the ribbon mic cables acting as antennas. It sounds like they've been pumping you full of nonsense. Graham |
#32
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:20 pm, Eeyore
wrote: Truth wrote: Eeyore wrote: Truth wrote: I have a ribbon microphone that is picking up AM radio. Now I'm just wondering what is picking up the interference, is it the mic itself, the mic cables, or the main power? I think you mean "I'm just wondering what is demodulating the interference" and the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if it's there, the trick is not to demodulate it. What's the mic ? What's your preamp / mixer / interface ? Graham Interesting. Could the problem perhaps originate in the power, get transferred and made worse on the way to the computer? Not really. My chain: House Power Ribbon Mic's Power Box Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some strange 'head amplifier'. I wouln't mind betting there's your problem. Ribbon Mic's non standard cable, very long about 20 feet( I can't swap it out to test it with something else) What do you mean by non-standard ? Alarm bells are ringing already. 2 Royer 122V Ribbon Mics DH Labs 6 feet 110 Ohm XLR Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs with both) DH Labs 12 feet to Computer Sound card DI A DH Labs DI ? I can't find anything by googling. Is it active or passive ? Graham The cable connecting the ribbon mic to it's dedicated power supply is a 7 pin cable provided by Royer Labs. Could the problem originate in the power and get intensified by the Mic's Power Supply and cables, or the mic itself? |
#33
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:06 pm, Truth wrote:
These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. If that is the case, then what can be done about it? Move. Could the problem originate in the power source and made worse by long cable runs? That's the easiest part to RF-proof, and I suspect that they've done a reasonable job of it, but I don't know for sure. The RF could be being picked up by the microphone element itself (there's only so much shielding they can do and still let sound in), but it's not likely that the cable is the problem. The output of the microphone is a cathode follower, which I suspect does not go through a transformer, at least not until it gets into the power supply box. That means an unbalanced cable run which, even though it's a low impedance source (the tube in the microphone) can still act as an antenna. The output of the system is balanced, but it's not clear from the data I have available where the balancing occurs. So you may very well have a 20 foot antenna ahead of your mic preamp. Or, if the RF field strength is great enough, the tube in the mic could be acting like a diode and detecting the radio signal. You should try taking the mics and a preamp somewhere else. You don't need the whole computer rig, just a set of headphones. |
#34
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:31 pm, Mike Rivers wrote:
On Sep 13, 12:06 pm, Truth wrote: These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. If that is the case, then what can be done about it? Move. Could the problem originate in the power source and made worse by long cable runs? That's the easiest part to RF-proof, and I suspect that they've done a reasonable job of it, but I don't know for sure. The RF could be being picked up by the microphone element itself (there's only so much shielding they can do and still let sound in), but it's not likely that the cable is the problem. The output of the microphone is a cathode follower, which I suspect does not go through a transformer, at least not until it gets into the power supply box. That means an unbalanced cable run which, even though it's a low impedance source (the tube in the microphone) can still act as an antenna. The output of the system is balanced, but it's not clear from the data I have available where the balancing occurs. So you may very well have a 20 foot antenna ahead of your mic preamp. Or, if the RF field strength is great enough, the tube in the mic could be acting like a diode and detecting the radio signal. You should try taking the mics and a preamp somewhere else. You don't need the whole computer rig, just a set of headphones. I'm able to monitor direct from the Pendulum preamp and I hear the squeal there before it gets to the computer. I'm thinking a shorter run mic cable between the power box and mic might help. |
#35
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Ribbon Mic picking up Radio Frequency Interference
On Thu, 13 Sep 2007 09:36:00 -0700, Truth
wrote: On Sep 13, 12:31 pm, Mike Rivers wrote: On Sep 13, 12:06 pm, Truth wrote: These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. If that is the case, then what can be done about it? Move. Could the problem originate in the power source and made worse by long cable runs? That's the easiest part to RF-proof, and I suspect that they've done a reasonable job of it, but I don't know for sure. The RF could be being picked up by the microphone element itself (there's only so much shielding they can do and still let sound in), but it's not likely that the cable is the problem. The output of the microphone is a cathode follower, which I suspect does not go through a transformer, at least not until it gets into the power supply box. That means an unbalanced cable run which, even though it's a low impedance source (the tube in the microphone) can still act as an antenna. The output of the system is balanced, but it's not clear from the data I have available where the balancing occurs. So you may very well have a 20 foot antenna ahead of your mic preamp. Or, if the RF field strength is great enough, the tube in the mic could be acting like a diode and detecting the radio signal. You should try taking the mics and a preamp somewhere else. You don't need the whole computer rig, just a set of headphones. I'm able to monitor direct from the Pendulum preamp and I hear the squeal there before it gets to the computer. I'm thinking a shorter run mic cable between the power box and mic might help. Before you are forced to anything drastic, try some clamp-on RF stoppers - the kind you find on the end of your VGA monitor cable. You can get these in most electronics parts houses. Go for the lowest frequency spec they have. Put them on all the cables (starting with the mic cable) close to the preamp, and see which stops, or at least reduces, the effect. d -- Pearce Consulting http://www.pearce.uk.com |
#36
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:27 pm, Eeyore
wrote: Truth wrote: These are two brand new Royer 122V Tube Ribbon Microphones. I sent the first two I received back to Royer Why ? Same problem or a different one ? and they sent me two brand new replacements. They told me to keep them away from dimmers, motors, fluorescent lights, etc. They also mentioned that the mics can act like antennas. They're talking crap. It probably means they know their design is defective. If that is the case, then what can be done about it? Reject them and buy something that works properly ? Could the problem originate in the power source If it was just a 'power source' it would be unlikely but it seems it contains some active electronics (i.e it has gain). Certainly that electronics could be defective. You sound a bit vague about understanding what you've bought. and made worse by long cable runs? Not really. I have to get in contact with them again and see what they say as well. Perhaps getting shorter ribbon mic cables will help, since you say the problem could be the ribbon mic cables acting as antennas. It sounds like they've been pumping you full of nonsense. Graham No they are correct. When my LCD monitor is on I can hear a definite hum or buzz. When I turn it off it goes away, so I turn it off while recording. Because the microphones use magnetism to function they are prone to these problems. They sound good when they work, so I'd like to try to see if the problem is not something other than the microphones first. |
#37
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:24 pm, "Richard Crowley" wrote:
"Truth" wrote ... It's a commercial station. 790 AM. I think the same station as some talk shows. When I could hear the station it was a Christian Radio Program. If you are hearing the same "squeal", interference, etc. on this radio receiver, why do you suspect anything is wrong with your audio equipment? Since we have no clue where you are "790 AM" means nothing to us. There are 100 radio stations on that freuency just in North America. That's the thing, I don't know what is the problem yet. It could be the house lines acting as antenna and not the equipment itself which is at fault. That's why I was asking if anyone thought the problem was originating at the power source. Take a look at this article: http://svconline.com/mag/avinstall_u...ontrolling_rf/ "Interference can also arrive via any wire coming into the building. " |
#38
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Ribbon Mic picking up Radio Frequency Interference
"Truth" wrote in message oups.com... Could the problem originate in the power and get intensified by the Mic's Power Supply and cables, or the mic itself? The mic's power supply is supposed to provide resistance to RF, and probably does. AFAIK, Royer are nobody's fools. RF usually doesn't come in on the power lines, nearly as often as it simply comes through the air. Power line circuitry tends to attenuate RF - as anybody who has tried to run an X-10 system knows. |
#39
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Ribbon Mic picking up Radio Frequency Interference
"Richard Crowley" wrote in message ... "Eeyore" wrote ... Something that I don't think we've yet touched on is that there may be some instability (oscillation) at very high frequencies in your equipment and it's mixing with the RF. That could cause a 'scream'. If he hears the same "squeal" in an independent radio receiver, it could be an indication of something wierd happening in his RF neighborhood. His audio recording equipment could be operating "nominally" and we are barking up the wrong tree. In many urban areas, AM receivers simply find assorted squeals. Especially true if there is a powerful transmitter nearby. |
#40
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Ribbon Mic picking up Radio Frequency Interference
On Sep 13, 12:22 pm, Eeyore
wrote: Truth wrote: I even got some special power cords for the mic power supplies. Why ? What did you expect it to do ? AC power doesn't need 'special cords'. They're only for gullible 'audiophools'. Graham Here are the cables I mentioned for the power supplies. http://www.silversonic.com/docs/products/PowerPlus.html |
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