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Question regarding Phantom Power
Hello everyone,
I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. |
#3
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On 24 Sep 2004 10:44:05 -0700, (Neil) wrote:
Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. d Pearce Consulting http://www.pearce.uk.com |
#4
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On 24 Sep 2004 10:44:05 -0700, (Neil) wrote:
Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. d Pearce Consulting http://www.pearce.uk.com |
#5
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Neil wrote:
The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. No. Microphones don't draw 48V of current. Voltage and current are different. Microphones draw a few milliamps of current at 48V. The more microphones you use, the more current (in milliamps) they draw. But they all have 48V across them, whether or not they draw any current. (Actually, when you put a current load on them, the voltage drops a bit.) The electrical outlets in your house all have 120V across them. You plug in more appliances, the current demand increases but the voltage stays the same. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. You want a good introduction to DC circuits. The Schaum's Outline is a pretty good one, as is the first chapter of The Art Of Electronics. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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Neil wrote:
The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. No. Microphones don't draw 48V of current. Voltage and current are different. Microphones draw a few milliamps of current at 48V. The more microphones you use, the more current (in milliamps) they draw. But they all have 48V across them, whether or not they draw any current. (Actually, when you put a current load on them, the voltage drops a bit.) The electrical outlets in your house all have 120V across them. You plug in more appliances, the current demand increases but the voltage stays the same. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. You want a good introduction to DC circuits. The Schaum's Outline is a pretty good one, as is the first chapter of The Art Of Electronics. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#7
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Neil wrote:
The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. No. Microphones don't draw 48V of current. Voltage and current are different. Microphones draw a few milliamps of current at 48V. The more microphones you use, the more current (in milliamps) they draw. But they all have 48V across them, whether or not they draw any current. (Actually, when you put a current load on them, the voltage drops a bit.) The electrical outlets in your house all have 120V across them. You plug in more appliances, the current demand increases but the voltage stays the same. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. You want a good introduction to DC circuits. The Schaum's Outline is a pretty good one, as is the first chapter of The Art Of Electronics. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#8
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In article ,
(Don Pearce) wrote: On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. you have 40(pulling a number out of my ass) 110 volt wall outlets in your house does this make them 4400 volt outlets if you use them all no they remain 110 volt outlets you just need to have enough amperage avaiable to drive the load each outlet is drawing George |
#9
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In article ,
(Don Pearce) wrote: On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. you have 40(pulling a number out of my ass) 110 volt wall outlets in your house does this make them 4400 volt outlets if you use them all no they remain 110 volt outlets you just need to have enough amperage avaiable to drive the load each outlet is drawing George |
#10
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In article ,
(Don Pearce) wrote: On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. you have 40(pulling a number out of my ass) 110 volt wall outlets in your house does this make them 4400 volt outlets if you use them all no they remain 110 volt outlets you just need to have enough amperage avaiable to drive the load each outlet is drawing George |
#11
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George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) |
#12
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George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) |
#13
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George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) |
#14
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In article ,
Don Cooper wrote: George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) ok I won't share where I keep the re20's george |
#15
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In article ,
Don Cooper wrote: George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) ok I won't share where I keep the re20's george |
#16
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In article ,
Don Cooper wrote: George wrote: you have 40(pulling a number out of my ass) 110 volt wall outlets in your house That's not a pretty image, George. : ) ok I won't share where I keep the re20's george |
#17
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Neil wrote:
I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. The problem is electricity is very counter-intuitive, and you have a misunderstanding about what voltage is. Voltage is not the same thing as power. Voltage is sometimes called "potential" (which is short for "potential difference"). You'll notice that "potential" and "power" represent very different ideas. When electrons are moving from point A to point B, you've got an electric current. But, the electrons aren't going to spontaenously all move in one direction as a group, so in order for this to happen, there must be a force that causes them to move. Voltage is connected with how much force there is available to possibly make the electrons move. I say "possibly" because another thing that's necessary is for there to be a path for electrons to take. Unless they are in just the right mood, electrons don't like to just fly across open space. (Normally this takes the form of metal, which works because electrons can move around within metal pretty easily, so one electron can move a little bit and nudge another electron, which then nudges another, and then pretty soon you've a bunch of electrons inching in one direction by tiny amounts.) Anyway, the point is that the amount of current that flows depends on how much the electrons "want" to move (related to voltage) *and* on how much resistance they encounter when trying to move. (Think of walking on a sidewalk vs. walking through very shallow water at the beach vs. walking through waist-deep water at the beach.) Anyway, to relate this back to the mixer, 48V just means that the electrons have 48V of "motivation" to work with IF they find a suitable, easy path along which to move. It doesn't mean that any of them are actually moving at all. If there is a perfect path where electrons encounter no resistance at all, and if the console has no limits on its ability to maintain 48V, then you would have infinite current. If, however, there is some resistance, then the current will be lower the higher the resistance is. The person who designs a microphone can make it get just the amount of current that it needs by designing a circuit with just the right resistance. By the way, as for why it's 48V, I think that has to do with a compromise. Higher-voltage circuits can transmit electricity over long distances with less energy loss and with thinner wires. Devices require various voltages, and on a DC circuit it's much easier to cut voltage than it is to increase it. So, 48V is high enough for most devices and it's easy to drop down if you need to. However, high voltages also are a little more difficult to deal with safely, and the government makes it easier to get things approved if they are not too high a voltage. (This is why people use "low-voltage lighting", i.e. "Malibu lights" for their front yard to light up trees and stuff.) So, 48V is a compromise between those factors. - Logan |
#18
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Neil wrote:
I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. The problem is electricity is very counter-intuitive, and you have a misunderstanding about what voltage is. Voltage is not the same thing as power. Voltage is sometimes called "potential" (which is short for "potential difference"). You'll notice that "potential" and "power" represent very different ideas. When electrons are moving from point A to point B, you've got an electric current. But, the electrons aren't going to spontaenously all move in one direction as a group, so in order for this to happen, there must be a force that causes them to move. Voltage is connected with how much force there is available to possibly make the electrons move. I say "possibly" because another thing that's necessary is for there to be a path for electrons to take. Unless they are in just the right mood, electrons don't like to just fly across open space. (Normally this takes the form of metal, which works because electrons can move around within metal pretty easily, so one electron can move a little bit and nudge another electron, which then nudges another, and then pretty soon you've a bunch of electrons inching in one direction by tiny amounts.) Anyway, the point is that the amount of current that flows depends on how much the electrons "want" to move (related to voltage) *and* on how much resistance they encounter when trying to move. (Think of walking on a sidewalk vs. walking through very shallow water at the beach vs. walking through waist-deep water at the beach.) Anyway, to relate this back to the mixer, 48V just means that the electrons have 48V of "motivation" to work with IF they find a suitable, easy path along which to move. It doesn't mean that any of them are actually moving at all. If there is a perfect path where electrons encounter no resistance at all, and if the console has no limits on its ability to maintain 48V, then you would have infinite current. If, however, there is some resistance, then the current will be lower the higher the resistance is. The person who designs a microphone can make it get just the amount of current that it needs by designing a circuit with just the right resistance. By the way, as for why it's 48V, I think that has to do with a compromise. Higher-voltage circuits can transmit electricity over long distances with less energy loss and with thinner wires. Devices require various voltages, and on a DC circuit it's much easier to cut voltage than it is to increase it. So, 48V is high enough for most devices and it's easy to drop down if you need to. However, high voltages also are a little more difficult to deal with safely, and the government makes it easier to get things approved if they are not too high a voltage. (This is why people use "low-voltage lighting", i.e. "Malibu lights" for their front yard to light up trees and stuff.) So, 48V is a compromise between those factors. - Logan |
#19
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Neil wrote:
I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. The problem is electricity is very counter-intuitive, and you have a misunderstanding about what voltage is. Voltage is not the same thing as power. Voltage is sometimes called "potential" (which is short for "potential difference"). You'll notice that "potential" and "power" represent very different ideas. When electrons are moving from point A to point B, you've got an electric current. But, the electrons aren't going to spontaenously all move in one direction as a group, so in order for this to happen, there must be a force that causes them to move. Voltage is connected with how much force there is available to possibly make the electrons move. I say "possibly" because another thing that's necessary is for there to be a path for electrons to take. Unless they are in just the right mood, electrons don't like to just fly across open space. (Normally this takes the form of metal, which works because electrons can move around within metal pretty easily, so one electron can move a little bit and nudge another electron, which then nudges another, and then pretty soon you've a bunch of electrons inching in one direction by tiny amounts.) Anyway, the point is that the amount of current that flows depends on how much the electrons "want" to move (related to voltage) *and* on how much resistance they encounter when trying to move. (Think of walking on a sidewalk vs. walking through very shallow water at the beach vs. walking through waist-deep water at the beach.) Anyway, to relate this back to the mixer, 48V just means that the electrons have 48V of "motivation" to work with IF they find a suitable, easy path along which to move. It doesn't mean that any of them are actually moving at all. If there is a perfect path where electrons encounter no resistance at all, and if the console has no limits on its ability to maintain 48V, then you would have infinite current. If, however, there is some resistance, then the current will be lower the higher the resistance is. The person who designs a microphone can make it get just the amount of current that it needs by designing a circuit with just the right resistance. By the way, as for why it's 48V, I think that has to do with a compromise. Higher-voltage circuits can transmit electricity over long distances with less energy loss and with thinner wires. Devices require various voltages, and on a DC circuit it's much easier to cut voltage than it is to increase it. So, 48V is high enough for most devices and it's easy to drop down if you need to. However, high voltages also are a little more difficult to deal with safely, and the government makes it easier to get things approved if they are not too high a voltage. (This is why people use "low-voltage lighting", i.e. "Malibu lights" for their front yard to light up trees and stuff.) So, 48V is a compromise between those factors. - Logan |
#20
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In article in rec.audio.pro on Fri, 24
Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. |
#21
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In article in rec.audio.pro on Fri, 24
Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. |
#22
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In article in rec.audio.pro on Fri, 24
Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. |
#23
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In article in rec.audio.pro on Fri,
24 Sep 2004 19:46:58 GMT, Logan Shaw says... By the way, as for why it's 48V, I think that has to do with a compromise. No, like the 600 ohms impedance, 48V comes to us from telephone technology. That is the voltage that phantom power on your telephone line uses. |
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In article in rec.audio.pro on Fri,
24 Sep 2004 19:46:58 GMT, Logan Shaw says... By the way, as for why it's 48V, I think that has to do with a compromise. No, like the 600 ohms impedance, 48V comes to us from telephone technology. That is the voltage that phantom power on your telephone line uses. |
#25
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In article in rec.audio.pro on Fri,
24 Sep 2004 19:46:58 GMT, Logan Shaw says... By the way, as for why it's 48V, I think that has to do with a compromise. No, like the 600 ohms impedance, 48V comes to us from telephone technology. That is the voltage that phantom power on your telephone line uses. |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: In article in rec.audio.pro on Fri, 24 Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. The maximum current that can flow even in a dead short is the result of the full 48 volts appearing across the 3000 ohms built into the system - that is 16mA and will do no harm. The little sparks you saw were the result of the 48volts. Pretty, but probably not a good thing to do during a session! (Hint: you can always switch the phantom off on the connectors you are working on ;-) Connecting one pin to ground is not a problem - as far as phantom power is concerned, the two mic pins are entirely separate. d Pearce Consulting http://www.pearce.uk.com |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: In article in rec.audio.pro on Fri, 24 Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. The maximum current that can flow even in a dead short is the result of the full 48 volts appearing across the 3000 ohms built into the system - that is 16mA and will do no harm. The little sparks you saw were the result of the 48volts. Pretty, but probably not a good thing to do during a session! (Hint: you can always switch the phantom off on the connectors you are working on ;-) Connecting one pin to ground is not a problem - as far as phantom power is concerned, the two mic pins are entirely separate. d Pearce Consulting http://www.pearce.uk.com |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: In article in rec.audio.pro on Fri, 24 Sep 2004 17:58:26 GMT, Don Pearce says... On 24 Sep 2004 10:44:05 -0700, (Neil) wrote: Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. I've searched for an answer to this question on the web, but I've found no answers. Hope someone can help me!. Thanks in advance, Neil. This is tricky - first we need to sort out your terminology a bit. 48V isn't a current - it is a voltage. It is available to any mic that needs it, but it is wired in a mode called parallel - that is it doesn't add up for every mic, it is just 48V - no more than that. On each mic channel it is fed to the mic through a pair of resistors of about 6000 ohms (3000 ohms equivalent) so any single mic can take up to 48/3000 or 0.016 amps (16mA). That is plenty for even the most demanding phantom mic - most take much less. SOme need more, and they come with their own power supply. But the point is that all microphones are guaranteed to work off that voltage and resistance combination, but most don't need that much. As for the desk, if you have, say 24 mic channels, then the 48V power supply must be able to supply 24 x .016 amps, or roughly half an amp. So you see it is the amps, not the volts, that build up as you add more microphones. How do most power supplies handle that all too possible situation of (a) an unintentional fault causing a short between the earth and signal pins (b) an intentional situation of connecting an unbalanced source that has pin 2 connected to ground, as is standard practice but which results in phantom shorted to earth? I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. The maximum current that can flow even in a dead short is the result of the full 48 volts appearing across the 3000 ohms built into the system - that is 16mA and will do no harm. The little sparks you saw were the result of the 48volts. Pretty, but probably not a good thing to do during a session! (Hint: you can always switch the phantom off on the connectors you are working on ;-) Connecting one pin to ground is not a problem - as far as phantom power is concerned, the two mic pins are entirely separate. d Pearce Consulting http://www.pearce.uk.com |
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Neil wrote:
Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, Volts isn't current it's *VOLTS* ! Current is *AMPS* Do you plan a career in pro-audio or the dole queue ? If the former, I suggest you go learn something about the fundamentals. but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. Checks just to make sure it isn't 1 April. What college is that ? Was the lecturer not present and able to answer ? I see that you're in the UK. If you had 4 x 240V power sockets in a room would you expect the mains supply to be 960V ? They let too many dim kids into college these days to make the numbers look good. Graham |
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Neil wrote:
Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, Volts isn't current it's *VOLTS* ! Current is *AMPS* Do you plan a career in pro-audio or the dole queue ? If the former, I suggest you go learn something about the fundamentals. but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. Checks just to make sure it isn't 1 April. What college is that ? Was the lecturer not present and able to answer ? I see that you're in the UK. If you had 4 x 240V power sockets in a room would you expect the mains supply to be 960V ? They let too many dim kids into college these days to make the numbers look good. Graham |
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Neil wrote:
Hello everyone, I hope someone out there can answer my question, and I hope it doesn't come across as too naieve!. The question is regarding Phantom Power. At college, there is a 32 track mixing console, each track has an individual 'phantom power' switch. The question arose in class that if every single track on the mixer had phantom power enabled and phantom power runs at +48V, would this equate to 1536V??, or isn't it as simple as that?. I realise most mic's wouldn't draw 48V of current, Volts isn't current it's *VOLTS* ! Current is *AMPS* Do you plan a career in pro-audio or the dole queue ? If the former, I suggest you go learn something about the fundamentals. but if that's the case, why is phantom power set at 48V if the microphones don't need that much to operate?. Checks just to make sure it isn't 1 April. What college is that ? Was the lecturer not present and able to answer ? I see that you're in the UK. If you had 4 x 240V power sockets in a room would you expect the mains supply to be 960V ? They let too many dim kids into college these days to make the numbers look good. Graham |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. Never solder in a powered circuit. In fact, there's good reason to not solder in an earth grounded circuit. Chris Hornbeck |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. Never solder in a powered circuit. In fact, there's good reason to not solder in an earth grounded circuit. Chris Hornbeck |
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On Sat, 25 Sep 2004 09:56:03 +1200, Patrick Dunford
wrote: I was working on a patch panel the other day. The desk was powered up and had phantom on. Every time I touched my earthed soldering iron to the signal pins there was a nice little blue spark from the phantom power. Never solder in a powered circuit. In fact, there's good reason to not solder in an earth grounded circuit. Chris Hornbeck |
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Do you plan a career in pro-audio or the dole queue ? If the former, I
suggest you go learn something about the fundamentals. BRBR Might could be that's exactly why he's in college, which, last I heard, still allowed questions to be asked. Scott Fraser |
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Do you plan a career in pro-audio or the dole queue ? If the former, I
suggest you go learn something about the fundamentals. BRBR Might could be that's exactly why he's in college, which, last I heard, still allowed questions to be asked. Scott Fraser |
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Do you plan a career in pro-audio or the dole queue ? If the former, I
suggest you go learn something about the fundamentals. BRBR Might could be that's exactly why he's in college, which, last I heard, still allowed questions to be asked. Scott Fraser |
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