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#1
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Phantom Power
Is the phantom power supplied by many PA boards used to power the active
(MOSFET) device commonly found in electret condenser mic elements? -- Randy Yates % "My Shangri-la has gone away, fading like Digital Signal Labs % the Beatles on 'Hey Jude'" % http://www.digitalsignallabs.com % 'Shangri-La', *A New World Record*, ELO |
#2
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Phantom Power
Randy Yates writes:
Is the phantom power supplied by many PA boards Sorry - I meant "many mixing boards". -- Randy Yates % "She tells me that she likes me very much, Digital Signal Labs % but when I try to touch, she makes it % all too clear." http://www.digitalsignallabs.com % 'Yours Truly, 2095', *Time*, ELO |
#3
Posted to rec.audio.tech
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Phantom Power
"Randy Yates" wrote ...
Is the phantom power supplied by many PA boards used to power the active (MOSFET) device commonly found in electret condenser mic elements? Yes. That is probably the most common use of phantom power today. It is also used to power the active circuitry (voltage and/or current amplification and/or impedance buffering, etc. etc.) for other kinds of mics such as some models that put out line-level for driving very long lines, and impedance conversion/voltage amplification for non- condenser mics like ribbons, etc. It is also used for charging the condenser element in non-electret microphones. Probably even more uses that I can't remember this morning. |
#4
Posted to rec.audio.tech
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Phantom Power
"Richard Crowley" writes:
"Randy Yates" wrote ... Is the phantom power supplied by many PA boards used to power the active (MOSFET) device commonly found in electret condenser mic elements? Yes. That is probably the most common use of phantom power today. It is also used to power the active circuitry (voltage and/or current amplification and/or impedance buffering, etc. etc.) for other kinds of mics such as some models that put out line-level for driving very long lines, and impedance conversion/voltage amplification for non- condenser mics like ribbons, etc. It is also used for charging the condenser element in non-electret microphones. Probably even more uses that I can't remember this morning. Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. And I guess that C = Q / V means V = 0 if Q = 0 (i.e., you have to power the bloody things). -- Randy Yates % "Rollin' and riding and slippin' and Digital Signal Labs % sliding, it's magic." % http://www.digitalsignallabs.com % 'Living' Thing', *A New World Record*, ELO |
#5
Posted to rec.audio.tech
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Phantom Power
"Randy Yates" wrote ...
Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. The original condenser mics were externally charged. Most higher-end condenser mics are still externally charged. I have a pair of Sony C-37 mics which use external voltage. They also have power supplies the size of a lunch-box to handle the power and output transformers and use a 6AU6 in the mic head for impedance buffering. http://www.rcrowley.com/SonyC37/index.htm While the charge-storing electret was first described back in the late 1800s, it wasn't used commercially for condenser microphones until the 1960s. And I guess that C = Q / V means V = 0 if Q = 0 (i.e., you have to power the bloody things). Exactly |
#6
Posted to rec.audio.tech
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Phantom Power
Randy Yates wrote:
"Richard Crowley" writes: "Randy Yates" wrote ... Is the phantom power supplied by many PA boards used to power the active (MOSFET) device commonly found in electret condenser mic elements? Yes. That is probably the most common use of phantom power today. It is also used to power the active circuitry (voltage and/or current amplification and/or impedance buffering, etc. etc.) for other kinds of mics such as some models that put out line-level for driving very long lines, and impedance conversion/voltage amplification for non- condenser mics like ribbons, etc. It is also used for charging the condenser element in non-electret microphones. Probably even more uses that I can't remember this morning. Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. And I guess that C = Q / V means V = 0 if Q = 0 (i.e., you have to power the bloody things). There is two more type of condensor mic which don't use DC at all: Both types use a low voltage RF generated by a low-noise RF oscillator. The mic capsule of a RF condensor mic is part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. In the other type of RF condensor mic the capacitance of the mic capsule is used to modulate the amplitude of the RF oscillator. Norbert |
#7
Posted to rec.audio.tech
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Phantom Power
Norbert Hahn writes:
Randy Yates wrote: "Richard Crowley" writes: "Randy Yates" wrote ... Is the phantom power supplied by many PA boards used to power the active (MOSFET) device commonly found in electret condenser mic elements? Yes. That is probably the most common use of phantom power today. It is also used to power the active circuitry (voltage and/or current amplification and/or impedance buffering, etc. etc.) for other kinds of mics such as some models that put out line-level for driving very long lines, and impedance conversion/voltage amplification for non- condenser mics like ribbons, etc. It is also used for charging the condenser element in non-electret microphones. Probably even more uses that I can't remember this morning. Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. And I guess that C = Q / V means V = 0 if Q = 0 (i.e., you have to power the bloody things). There is two more type of condensor mic which don't use DC at all: Both types use a low voltage RF generated by a low-noise RF oscillator. The mic capsule of a RF condensor mic is part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. Hey I really like that idea. In the other type of RF condensor mic the capacitance of the mic capsule is used to modulate the amplitude of the RF oscillator. Very cool. Thanks for the enlightenment, Norbert! -- Randy Yates % "Remember the good old 1980's, when Digital Signal Labs % things were so uncomplicated?" % 'Ticket To The Moon' http://www.digitalsignallabs.com % *Time*, Electric Light Orchestra |
#8
Posted to rec.audio.tech
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Phantom Power
On Sat, 17 Apr 2010 14:16:23 -0700, Richard Crowley wrote
(in article ): "Randy Yates" wrote ... Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. The original condenser mics were externally charged. Most higher-end condenser mics are still externally charged. I have a pair of Sony C-37 mics which use external voltage. They also have power supplies the size of a lunch-box to handle the power and output transformers and use a 6AU6 in the mic head for impedance buffering. http://www.rcrowley.com/SonyC37/index.htm While the charge-storing electret was first described back in the late 1800s, it wasn't used commercially for condenser microphones until the 1960s. Also, generally speaking, electret microphones don't have the specs of conventional condensers. Most are very shy on bass, most aren't as quiet as non-electret condenser mikes, nor will they handle as high SPLs. I don't believe that there is any real technical reason for this, I think it's more because electrets make up the bottom end of the condenser microphone price range. Also, I don't know about today, but early electret microphones were subject to losing their electret charge under adverse conditions of heat and humidity. C-37s are good mikes and are highly sought after, making them more valuable (in absolute dollars) now then they cost when they were new (I recently saw a C-37P on E-bay with a starting bid of $2,200). I used to record a major symphony orchestra with a pair of C-37Ps in X-Y mode (cardioid pattern) on a 7" stereo "T" bar and nothing else. When I play those recordings today (long since transfered from R-to-R tape to either DAT or CD), they STILL impress everyone who hears them. One thing that I always found rather fascinating about Sony's approach to multi-pattern pickup with these mikes was the fact that unlike modern mikes which use dual-capsules and matrixing to achieve the three basic patterns of cardioid, omnidirectional, and figure-of-eight, Sony used a single capsule and movable mechanical baffles inside the microphone to achieve two of these patterns; cardioid (which Sony called "uni-directional" and marked on the microphone case with a "U") and omnidirectional (which Sony called non-directional and marked it on the case with an "N"). I don't believe that either the C-37A or P ever did bi-directional or figure-of-eight. The C-37P had real advantages over the "A" in that because of it's solid-state electronics, it was able to use standard 48-volt phantom power. A later design, the C-37FET actually could use an internal nine-volt transistor radio battery of the kind that were once so ubiquitous that Radio Shack gave them away! It would also run on regular 48-volt phantom power, if one preferred. The other advantage of the C-37P over the C-37A was that the solid-state electronics made the newer mike somewhat less noisy than its predecessor. The microphone I always wanted was a a pair of Sony C-500s. These strange looking mikes with their oddly spherical head, had a frequency response graph that looked like it was drawn with a ruler. 20-20KHz +/- 3dB with none of the customary rising top-end characteristics peaking at around 16KHz (like the C-37s). |
#9
Posted to rec.audio.tech
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Phantom Power
On Sat, 17 Apr 2010 14:58:30 -0700, Norbert Hahn wrote
(in article ): Randy Yates wrote: "Richard Crowley" writes: "Randy Yates" wrote ... Is the phantom power supplied by many PA boards used to power the active (MOSFET) device commonly found in electret condenser mic elements? Yes. That is probably the most common use of phantom power today. It is also used to power the active circuitry (voltage and/or current amplification and/or impedance buffering, etc. etc.) for other kinds of mics such as some models that put out line-level for driving very long lines, and impedance conversion/voltage amplification for non- condenser mics like ribbons, etc. It is also used for charging the condenser element in non-electret microphones. Probably even more uses that I can't remember this morning. Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. And I guess that C = Q / V means V = 0 if Q = 0 (i.e., you have to power the bloody things). There is two more type of condensor mic which don't use DC at all: Both types use a low voltage RF generated by a low-noise RF oscillator. The mic capsule of a RF condensor mic is part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. In the other type of RF condensor mic the capacitance of the mic capsule is used to modulate the amplitude of the RF oscillator. Norbert These were somewhat common back in the 1940's and 1950's but are rare (if not outright non-existent) today. Scheops and Altec Lansing both made RF condenser mikes in that era. The most famous one was an Altec model 21 which was long and slim and very futuristic looking (some call it the "Coke-bottle" microphone because it had a pinched waist sort of like a Coke bottle). If you rent the movie, "The Cain Mutiny" there is a scene in a nightclub near the beginning of the film, where the female love interest is singing " I can't believe that you're in love with me". She's holding one of these mikes. It's an anachronism because this is supposed to WWII era and I don't think this mike came out until about 1952. On a related note, in the 1950's, a company called Weathers built a phonograph pickup system that worked on this same principle. Weathers called it the "FM Pickup" because it used RF modulated by the stylus moving a capacitive element to generate the audio signal. The thing had to be bought as a system and consisted of the "cartridge", the arm, and the RF box. It's advantages were low tracking force (1 gram), very wide, flat frequency response, and theoretically, low distortion (because the capacitive element was push-pull). In reality, the tuning of the RF was incredibly touchy and even simple things like changes in humidity and temperature could de-tune the damned thing, at which point, intermodulation distortion went through the roof. One also couldn't fit any other cartridge to the arm. A friend of my father' had one (mono, of course) and as I recall, when it was working right, it sounded better than anything else in it's era. |
#10
Posted to rec.audio.tech
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Phantom Power
Audio Empire wrote:
On Sat, 17 Apr 2010 14:58:30 -0700, Norbert Hahn wrote (in article ): [snip] There is two more type of condensor mic which don't use DC at all: Both types use a low voltage RF generated by a low-noise RF oscillator. The mic capsule of a RF condensor mic is part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. In the other type of RF condensor mic the capacitance of the mic capsule is used to modulate the amplitude of the RF oscillator. These were somewhat common back in the 1940's and 1950's but are rare (if not outright non-existent) today. Have a look at Sennheiser's MKH series. Sennheiser started the series in the late 1980s in order to make low noise mics. MKH-20...-50 for studio purposes were the start. MKH-60 was aimed at long distance recording (video support). Later the MKH-46x series was added and in 2000 the MKH-80xx series appeared. [snip] On a related note, in the 1950's, a company called Weathers built a phonograph pickup system that worked on this same principle. Weathers called it the "FM Pickup" because it used RF modulated by the stylus moving a capacitive element to generate the audio signal. The thing had to be bought as a system and consisted of the "cartridge", the arm, and the RF box. It's advantages were low tracking force (1 gram), very wide, flat frequency response, and theoretically, low distortion (because the capacitive element was push-pull). In reality, the tuning of the RF was incredibly touchy and even simple things like changes in humidity and temperature could de-tune the damned thing, at which point, intermodulation distortion went through the roof. One also couldn't fit any other cartridge to the arm. A friend of my father' had one (mono, of course) and as I recall, when it was working right, it sounded better than anything else in it's era. Thanks for this report! Norbert |
#11
Posted to rec.audio.tech
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Phantom Power
Norbert Hahn wrote:
Have a look at Sennheiser's MKH series. Sennheiser started the series in the late 1980s in order to make low noise mics. MKH-20...-50 for studio purposes were the start. MKH-60 was aimed at long distance recording (video support). Later the MKH-46x series was added and in 2000 the MKH-80xx series appeared. I think the measurment mike MKH106 was the first model and that they go back at least to the 1960'es since they were "classics" in the early 1970'ties when I got involved with recording. Norbert Kind regards Peter Larsen |
#12
Posted to rec.audio.tech
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Phantom Power
"Audio Empire" wrote...
Also, generally speaking, electret microphones don't have the specs of conventional condensers. Most are very shy on bass, most aren't as quiet as non-electret condenser mikes, nor will they handle as high SPLs. I don't believe that there is any real technical reason for this, I think it's more because electrets make up the bottom end of the condenser microphone price range. Also, I don't know about today, but early electret microphones were subject to losing their electret charge under adverse conditions of heat and humidity. Note that some of the most highly regarded (and highest priced) mics made by DPA are electret. |
#13
Posted to rec.audio.tech
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Phantom Power
"Audio Empire" wrote...
There is two more type of condensor mic which don't use DC at all: Both types use a low voltage RF generated by a low-noise RF oscillator. The mic capsule of a RF condensor mic is part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. In the other type of RF condensor mic the capacitance of the mic capsule is used to modulate the amplitude of the RF oscillator. Norbert These were somewhat common back in the 1940's and 1950's but are rare (if not outright non-existent) today. I just bought a Rode NTG-3 shotgun mic which was just introduced late last year. It is being favorably compared to several of the long- established industry-standard shotgun mics. It uses the RF oscillator design, so the circuit appears to be still going strong. |
#14
Posted to rec.audio.tech
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Phantom Power
"Audio Empire" wrote in message
.com On Sat, 17 Apr 2010 14:16:23 -0700, Richard Crowley wrote (in article ): "Randy Yates" wrote ... Thanks for the confirmation and education, Richard! Before you wrote this, I didn't even know there were "non-electret" condenser mics. The original condenser mics were externally charged. Most higher-end condenser mics are still externally charged. I have a pair of Sony C-37 mics which use external voltage. They also have power supplies the size of a lunch-box to handle the power and output transformers and use a 6AU6 in the mic head for impedance buffering. http://www.rcrowley.com/SonyC37/index.htm While the charge-storing electret was first described back in the late 1800s, it wasn't used commercially for condenser microphones until the 1960s. Also, generally speaking, electret microphones don't have the specs of conventional condensers. Really? Are you aware that DPA measurement mics are based on electret elements? Most are very shy on bass, most aren't as quiet as non-electret condenser mikes, nor will they handle as high SPLs. There's no evidence to prove these unbelievably sweeping statements. I don't believe that there is any real technical reason for this, You're right about that! I think it's more because electrets make up the bottom end of the condenser microphone price range. Electret microphones do make up much of the absolute economic bottom end of microphone technology, such as the mics in portable dictation devices and cell phones. Also, I don't know about today, but early electret microphones were subject to losing their electret charge under adverse conditions of heat and humidity. Still true, but externally-charged mics have plenty temperatature and humidity-induced variations of their own. |
#15
Posted to rec.audio.tech
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Phantom Power
Dick Pierce wrote:
In addition to the other uses cited elsewhere, so-called RF microphone carrier systems are used for instrumentation purposes notably where extremely low frequency reponse is required. I remember the big Sennheiser Brochure mentioning that MKH106's were available in version with a lower response limit of 1 or 0.1 Hz on special order. Referring again to Bruel & Kjaer, their microphone carrier system with an appropriate capsule is capable of measuring down to frrequencies approaching DC (i.e., it can act like an electronic baramoeter), while still maintaining response up to 150 kHz. Used with something like a B&K 4147 capsule, you have an acoustica measuring system with response from under 0.01 Hz to over 20 kHz within a 2 dB envelope. Ahem, yes, they like their transducerspecs to meet or exceed exceed normal semiconductor circuit specs ... O;-) Kind regards Peter Larsen |
#16
Posted to rec.audio.tech
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Phantom Power
On Sun, 18 Apr 2010 22:19:18 -0700, Richard Crowley wrote
(in article ): "Audio Empire" wrote... Also, generally speaking, electret microphones don't have the specs of conventional condensers. Most are very shy on bass, most aren't as quiet as non-electret condenser mikes, nor will they handle as high SPLs. I don't believe that there is any real technical reason for this, I think it's more because electrets make up the bottom end of the condenser microphone price range. Also, I don't know about today, but early electret microphones were subject to losing their electret charge under adverse conditions of heat and humidity. Note that some of the most highly regarded (and highest priced) mics made by DPA are electret. Like I said, I'm aware of no technical reason why electrets shouldn't be capable of just as good performance as a non-electret condenser mike. I suspect it's just because we encounter electret mikes mostly at the consumer end of the price scale. |
#17
Posted to rec.audio.tech
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Phantom Power
"Audio Empire" wrote in message
.com... On Sun, 18 Apr 2010 22:19:18 -0700, Richard Crowley wrote (in article ): "Audio Empire" wrote... Also, generally speaking, electret microphones don't have the specs of conventional condensers. Most are very shy on bass, most aren't as quiet as non-electret condenser mikes, nor will they handle as high SPLs. I don't believe that there is any real technical reason for this, I think it's more because electrets make up the bottom end of the condenser microphone price range. Also, I don't know about today, but early electret microphones were subject to losing their electret charge under adverse conditions of heat and humidity. Note that some of the most highly regarded (and highest priced) mics made by DPA are electret. Like I said, I'm aware of no technical reason why electrets shouldn't be capable of just as good performance as a non-electret condenser mike. I suspect it's just because we encounter electret mikes mostly at the consumer end of the price scale. I forwarded a couple posts from this thread to a friend - John Hausback from Electronic Wizards in Wichita KS. His reply: "While I agree with Richard Crowley that an electret condenser will never sound like a good vintage mic, it is capable of sounding better than it's reputation would suggest. One of the secrets is in liberating it's power supply. Most electrets are crippled by that damned 1.5V battery the engineers insist on shoving up them. While the FET buffer in the capsule will run with a volt and a half supply, I find you get better breathing room using a supply of a higher voltage. Another secret in making them sound better is in using a buffer after the element to isolate it from the outside world. I posted a design for such a mic to the geekslutz forum on gearslutz.com some time back. The link can be found here. http://www.gearslutz.com/board/geeks...icrophone.html Due to size constraints, the buffer is in a seperate box. The design is such that when the mic is unplugged from the buffer, the buffer turns itself off. This is acomplished without using a mechanical switch. "Off" leakage is such that the battery enjoys normal shelf life. Try this and you will find that powering an electret element with a AAA cell or equivalent is like running a NASCAR engine with a throttle plate." John |
#18
Posted to rec.audio.tech
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Phantom Power
"Mark Zacharias" writes:
[...] Mark, thanks much for the design hints! --Randy -- Randy Yates % "She has an IQ of 1001, she has a jumpsuit Digital Signal Labs % on, and she's also a telephone." % http://www.digitalsignallabs.com % 'Yours Truly, 2095', *Time*, ELO |
#19
Posted to rec.audio.tech
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Phantom Power
"Mark Zacharias" wrote ...
[quoting John Hausback]... "While I agree with Richard Crowley that an electret condenser will never sound like a good vintage mic, it is capable of sounding better than it's reputation would suggest. I think someone else said that. If I had an unlimited budget, I would have a collection of high-voltage (electret!) mics from DPA for my live location recording of choirs and orchestras. One of the secrets is in liberating it's power supply. Most electrets are crippled by that damned 1.5V battery the engineers insist on shoving up them. While the FET buffer in the capsule will run with a volt and a half supply, I find you get better breathing room using a supply of a higher voltage. Another secret in making them sound better is in using a buffer after the element to isolate it from the outside world. I posted a design for such a mic to the geekslutz forum on gearslutz.com some time back. The link can be found here. Note that there is a whole web-based discussion group just for people who DIY microphones: http://tech.groups.yahoo.com/group/micbuilders/ They have a rather decent collection of info including schematics of microphones vintage and modern. Mostly using commercial electret mic capsules, but occasionally, more ventursome projects are discussed. |
#20
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Phantom Power
"Randy Yates" wrote in message
.. . "Mark Zacharias" writes: [...] Mark, thanks much for the design hints! --Randy -- Randy Yates % "She has an IQ of 1001, she has a jumpsuit Digital Signal Labs % on, and she's also a telephone." % http://www.digitalsignallabs.com % 'Yours Truly, 2095', *Time*, ELO Credit John Hausback, my friend and co-conspirator at Electronic Wizards in Wichita. I must get him to subscribe to a couple newsgroups. He a valuable guy. Mark Z. |
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