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#81
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I'm guessing that
he didn't get an answer in class and that's why he asked here. BRBR Yeah, unfortunately some self-certified superior being had to slam the kid for not already knowing the answer to the question he was asking. Scott Fraser |
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#82
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#83
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#84
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Mike Rivers wrote: In article writes: The 48 VDC is voltage..and we assume that it's really 48 and is stabilized, so adding more mics doesn't load the circuit down to something less than 48VDC. Different condenser mics have different power requirements. Some need more mA (millamps) than others. Some console power supplies are not designed to properly power all mics. The result is increased distortion and lower headroom on the mics themselves. It's not hard to build a power supply with sufficient current capacity to handle any reasonable number of microphones, and most well designed consoles are so equipped. However, when it comes to budget-priced consoles, often the 48 volt supply is a low power DC-DC converter running off the op-amp power supply. Actually Mike, I know of no such instance and I'm pretty familiar with the 'usual suspects' in the low cost console arena. Truth is, a DC-DC converter tends to be quite expensive. It's much easier/cheaper to put an extra tap on the power supply transformer or use a 'charge pump' arrangement to derive a 'high voltage' from the AC used for the op-amp supplies. This is considerably less expensive than using a separate power transformer or a transformer with a separate winding for the 48V power supply (wall-wart power is a dead giveaway) but rarely provides enough current for a "full house" of microphones. Errr.. it seems I disagree ( have never seen this - the dc to dc converter - used in any of the major brands of budget desks ). The charge pump is historically popular and is the arrangment usually least likely to be able to power many mics due to its poor regulation of the ( pre 48V regulator ic ) unregulated high voltage supply vs load current ( supply droop ). Graham |
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#85
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Mike Rivers wrote: In article writes: The 48 VDC is voltage..and we assume that it's really 48 and is stabilized, so adding more mics doesn't load the circuit down to something less than 48VDC. Different condenser mics have different power requirements. Some need more mA (millamps) than others. Some console power supplies are not designed to properly power all mics. The result is increased distortion and lower headroom on the mics themselves. It's not hard to build a power supply with sufficient current capacity to handle any reasonable number of microphones, and most well designed consoles are so equipped. However, when it comes to budget-priced consoles, often the 48 volt supply is a low power DC-DC converter running off the op-amp power supply. Actually Mike, I know of no such instance and I'm pretty familiar with the 'usual suspects' in the low cost console arena. Truth is, a DC-DC converter tends to be quite expensive. It's much easier/cheaper to put an extra tap on the power supply transformer or use a 'charge pump' arrangement to derive a 'high voltage' from the AC used for the op-amp supplies. This is considerably less expensive than using a separate power transformer or a transformer with a separate winding for the 48V power supply (wall-wart power is a dead giveaway) but rarely provides enough current for a "full house" of microphones. Errr.. it seems I disagree ( have never seen this - the dc to dc converter - used in any of the major brands of budget desks ). The charge pump is historically popular and is the arrangment usually least likely to be able to power many mics due to its poor regulation of the ( pre 48V regulator ic ) unregulated high voltage supply vs load current ( supply droop ). Graham |
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#86
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ScotFraser wrote:
I'm guessing that he didn't get an answer in class and that's why he asked here. BRBR Yeah, unfortunately some self-certified superior being had to slam the kid for not already knowing the answer to the question he was asking. In the UK ( where the OP posted from ) - it's normal to have passed some relevant exams before going to college. I think there's a difference between UK and US usage here. I believe that in the US you can go to 'college' at an earlier age with less academic knowledge. We don't have compatible schemes of education and assessment of ability but I would expect anyone attending one of the very few UK audio courses to be (a) lucky to be there (b) to have some knowledge of electricity that already includes volts and amps. The absence, apparently, of (b) reinforces my opinion that UK higher education is going to the dogs. Graham |
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#87
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ScotFraser wrote:
I'm guessing that he didn't get an answer in class and that's why he asked here. BRBR Yeah, unfortunately some self-certified superior being had to slam the kid for not already knowing the answer to the question he was asking. In the UK ( where the OP posted from ) - it's normal to have passed some relevant exams before going to college. I think there's a difference between UK and US usage here. I believe that in the US you can go to 'college' at an earlier age with less academic knowledge. We don't have compatible schemes of education and assessment of ability but I would expect anyone attending one of the very few UK audio courses to be (a) lucky to be there (b) to have some knowledge of electricity that already includes volts and amps. The absence, apparently, of (b) reinforces my opinion that UK higher education is going to the dogs. Graham |
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#88
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Patrick Dunford wrote:
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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) Graham |
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#89
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Patrick Dunford wrote:
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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) Graham |
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#90
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ScotFraser wrote: I'm guessing that he didn't get an answer in class and that's why he asked here. BRBR Yeah, unfortunately some self-certified superior being had to slam the kid for not already knowing the answer to the question he was asking. Yeah - and if doesn't know his volts from his amps - all those long winded explanations about V=IR will be lost on him I hate to see good education wasted on those who clearly don't have a clue about the subject. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. Graham |
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#91
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ScotFraser wrote: I'm guessing that he didn't get an answer in class and that's why he asked here. BRBR Yeah, unfortunately some self-certified superior being had to slam the kid for not already knowing the answer to the question he was asking. Yeah - and if doesn't know his volts from his amps - all those long winded explanations about V=IR will be lost on him I hate to see good education wasted on those who clearly don't have a clue about the subject. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. Graham |
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#92
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I hate to see good education wasted on those who clearly don't have a clue
about the subject. This would appear to be a perfect example of the previously mentioned difference between US & UK notions of higher education. In the US the assumption is one attends college to learn what one doesn't already know. Seems the UK version is more of an advanced degree in a subject already mastered. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. We don't have dossers in the US, but it's generally the lame timewasters who DON'T attend college (with the prominent exception of GW Bush.) Scott Fraser |
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#93
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I hate to see good education wasted on those who clearly don't have a clue
about the subject. This would appear to be a perfect example of the previously mentioned difference between US & UK notions of higher education. In the US the assumption is one attends college to learn what one doesn't already know. Seems the UK version is more of an advanced degree in a subject already mastered. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. We don't have dossers in the US, but it's generally the lame timewasters who DON'T attend college (with the prominent exception of GW Bush.) Scott Fraser |
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#94
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#96
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Mike Rivers wrote:
I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. A voltage multiplier circuit, the one with the cleverly-arranged caps and diodes. It doesn't need a transformer, so it's frequently a square-wave generator going to an electrolytic which charges through one diode then discharges through another diode into another cap. It can be cascaded to make triplers, quadruplers, etc, or negative supplies. Maxim makes EIA-232 driver chips that have this built in, to make +/- 12v from +5v. If you follow the electrons around the circuit over several cycles, a mental image of a positive-displacement water pump may appear, hence the name. |
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#97
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Mike Rivers wrote:
I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. A voltage multiplier circuit, the one with the cleverly-arranged caps and diodes. It doesn't need a transformer, so it's frequently a square-wave generator going to an electrolytic which charges through one diode then discharges through another diode into another cap. It can be cascaded to make triplers, quadruplers, etc, or negative supplies. Maxim makes EIA-232 driver chips that have this built in, to make +/- 12v from +5v. If you follow the electrons around the circuit over several cycles, a mental image of a positive-displacement water pump may appear, hence the name. |
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#98
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"Mike Rivers" wrote ...
I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." a.k.a. "voltage multiplier", a clever series of capacitors and diodes explained: http://www.tpub.com/neets/book7/27m.htm et. al. |
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#99
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"Mike Rivers" wrote ...
I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." a.k.a. "voltage multiplier", a clever series of capacitors and diodes explained: http://www.tpub.com/neets/book7/27m.htm et. al. |
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#100
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S O'Neill wrote:
Mike Rivers wrote: I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. A voltage multiplier circuit, the one with the cleverly-arranged caps and diodes. It doesn't need a transformer, so it's frequently a square-wave generator going to an electrolytic which charges through one diode then discharges through another diode into another cap. It can be cascaded to make triplers, quadruplers, etc, or negative supplies. Maxim makes EIA-232 driver chips that have this built in, to make +/- 12v from +5v. If you follow the electrons around the circuit over several cycles, a mental image of a positive-displacement water pump may appear, hence the name. This is also very commonly built with a 555 timer in order to get small amounts of higher voltages without using a hybrid converter module. Many microphones use similar circuits inside to crank the 48V phantom up to a higher voltage to polarize the capsule. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#101
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S O'Neill wrote:
Mike Rivers wrote: I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. A voltage multiplier circuit, the one with the cleverly-arranged caps and diodes. It doesn't need a transformer, so it's frequently a square-wave generator going to an electrolytic which charges through one diode then discharges through another diode into another cap. It can be cascaded to make triplers, quadruplers, etc, or negative supplies. Maxim makes EIA-232 driver chips that have this built in, to make +/- 12v from +5v. If you follow the electrons around the circuit over several cycles, a mental image of a positive-displacement water pump may appear, hence the name. This is also very commonly built with a 555 timer in order to get small amounts of higher voltages without using a hybrid converter module. Many microphones use similar circuits inside to crank the 48V phantom up to a higher voltage to polarize the capsule. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#102
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#103
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#104
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In article in rec.audio.pro on Sun, 26
Sep 2004 01:42:42 +0100, Pooh Bear says... Patrick Dunford wrote: 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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) It's called phantom in both cases because it doesn't use extra wires to carry the power. |
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#105
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In article in rec.audio.pro on Sun, 26
Sep 2004 01:42:42 +0100, Pooh Bear says... Patrick Dunford wrote: 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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) It's called phantom in both cases because it doesn't use extra wires to carry the power. |
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#106
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ScotFraser wrote:
I hate to see good education wasted on those who clearly don't have a clue about the subject. This would appear to be a perfect example of the previously mentioned difference between US & UK notions of higher education. In the US the assumption is one attends college to learn what one doesn't already know. Seems the UK version is more of an advanced degree in a subject already mastered. In the UK it would tend to be more of an advanced course at college in a subject that the student already has some knowledge of. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. We don't have dossers in the US, but it's generally the lame timewasters who DON'T attend college (with the prominent exception of GW Bush.) We get that too but here, sadly, college / university education is no longer the province of those who intend to use it to further their career opportunities. A degree is also certainly not anything like an almost guaranteed job ticket anymore. Of those I know who have passed degrees in recent years - not *one* has obtained a job in the subject studied. Some have simply become bar or shop staff. This is what happens when you devaluate further education. Graham |
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#107
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ScotFraser wrote:
I hate to see good education wasted on those who clearly don't have a clue about the subject. This would appear to be a perfect example of the previously mentioned difference between US & UK notions of higher education. In the US the assumption is one attends college to learn what one doesn't already know. Seems the UK version is more of an advanced degree in a subject already mastered. In the UK it would tend to be more of an advanced course at college in a subject that the student already has some knowledge of. Education was once seen as a privilege - not an excuse for lame timewasters with no clue to act the dosser. We don't have dossers in the US, but it's generally the lame timewasters who DON'T attend college (with the prominent exception of GW Bush.) We get that too but here, sadly, college / university education is no longer the province of those who intend to use it to further their career opportunities. A degree is also certainly not anything like an almost guaranteed job ticket anymore. Of those I know who have passed degrees in recent years - not *one* has obtained a job in the subject studied. Some have simply become bar or shop staff. This is what happens when you devaluate further education. Graham |
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#108
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Mike Rivers wrote:
In article writes: Errr.. it seems I disagree ( have never seen this - the dc to dc converter - used in any of the major brands of budget desks ). The charge pump is historically popular and is the arrangment usually least likely to be able to power many mics due to its poor regulation of the ( pre 48V regulator ic ) unregulated high voltage supply vs load current ( supply droop ). I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. That'll be the classic 'voltage doubler ( tripler) ' that uses capacitive coupling of the ac input to a further rectifier stage that 'sits on top of' the + rail bulk reservoir cap. A.k.a charge pump. No oscillator/transformer as you say. Graham |
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#109
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Mike Rivers wrote:
In article writes: Errr.. it seems I disagree ( have never seen this - the dc to dc converter - used in any of the major brands of budget desks ). The charge pump is historically popular and is the arrangment usually least likely to be able to power many mics due to its poor regulation of the ( pre 48V regulator ic ) unregulated high voltage supply vs load current ( supply droop ). I'm not familiar with the term "charge pump" but that's probably what I was thinking of when I said "DC-to-DC Converter." I haven't seen the classic oscillator/transformer/rectifier circuit used in this application, but I have seen tricks where the op-amp power supply has been goosed up without transformers. That'll be the classic 'voltage doubler ( tripler) ' that uses capacitive coupling of the ac input to a further rectifier stage that 'sits on top of' the + rail bulk reservoir cap. A.k.a charge pump. No oscillator/transformer as you say. Graham |
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#110
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Patrick Dunford wrote:
In article in rec.audio.pro on Sun, 26 Sep 2004 01:42:42 +0100, Pooh Bear says... Patrick Dunford wrote: 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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) It's called phantom in both cases because it doesn't use extra wires to carry the power. Well, originally the notion was to "phantom" a telegraph line in top of a telephone circuit by DC signalling between ground and both sides of the telephone line. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#111
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Patrick Dunford wrote:
In article in rec.audio.pro on Sun, 26 Sep 2004 01:42:42 +0100, Pooh Bear says... Patrick Dunford wrote: 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. There's nothing *phantom* about it - lol ! Only 2 wires used in telephony :-) It's called phantom in both cases because it doesn't use extra wires to carry the power. Well, originally the notion was to "phantom" a telegraph line in top of a telephone circuit by DC signalling between ground and both sides of the telephone line. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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