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#1
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In-line mike preamp
What the world needs is a cheap, battery operated stereo mike preamp
with fixed gain that will goose up a condenser mike to line levels. The unit I'm imagining would run from a pair of AA batteries, have a 1/8" TRS stereo jack for the input, and a cable with the same type plug on the other end. It would have "plug-in power" for low-priced mikes and a gain that could be changed internally to suit the particular mike. It would be priced somewhere between $50 and $100. If it already exists, would someone please direct me to it. Thanks, Norm Strong |
#2
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normanstrong wrote:
What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. Fixed gain would not work for many situations depending on the levels involved. The unit I'm imagining would run from a pair of AA batteries That's going to limit your output level and lower your S/N unless you use a DC-DC converter to drive the opamp (not likely at that price.) 1/8" TRS stereo jack for the input, and a cable with the same type plug on the other end. It would have "plug-in power" for low-priced mikes and a gain that could be changed internally to suit the particular mike. It would be priced somewhere between $50 and $100. http://www.soundprofessionals.com/cgi-bin/gold/item/SP-PREAMP but the price is higher than you want. They did have some closeouts of an earlier version awhile back. |
#3
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normanstrong wrote:
What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. Fixed gain would not work for many situations depending on the levels involved. The unit I'm imagining would run from a pair of AA batteries That's going to limit your output level and lower your S/N unless you use a DC-DC converter to drive the opamp (not likely at that price.) 1/8" TRS stereo jack for the input, and a cable with the same type plug on the other end. It would have "plug-in power" for low-priced mikes and a gain that could be changed internally to suit the particular mike. It would be priced somewhere between $50 and $100. http://www.soundprofessionals.com/cgi-bin/gold/item/SP-PREAMP but the price is higher than you want. They did have some closeouts of an earlier version awhile back. |
#4
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#6
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Sugarite wrote: What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. The unit I'm imagining would run from a pair of AA batteries, have a 1/8" TRS stereo jack for the input, and a cable with the same type plug on the other end. It would have "plug-in power" for low-priced mikes and a gain that could be changed internally to suit the particular mike. It would be priced somewhere between $50 and $100. If it already exists, would someone please direct me to it. Radio Shack Boosteroo, designed for boosting headphone levels, replace male input plug with female jack and use it backwards. For better results in that price range, buy two used DOD mosfet preamp pedals at around $25-30 each, hack the guts to fit into an appropriate smaller case and provide suitable voltage to the mics, it can all run off one 9V battery, preferably lithium. It'll sound as good as the preamps you'd find in a typical Behringer/Mackie caliber board. What is the gain and the noise EIN for each of these options? Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#7
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Sugarite wrote: What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. The unit I'm imagining would run from a pair of AA batteries, have a 1/8" TRS stereo jack for the input, and a cable with the same type plug on the other end. It would have "plug-in power" for low-priced mikes and a gain that could be changed internally to suit the particular mike. It would be priced somewhere between $50 and $100. If it already exists, would someone please direct me to it. Radio Shack Boosteroo, designed for boosting headphone levels, replace male input plug with female jack and use it backwards. For better results in that price range, buy two used DOD mosfet preamp pedals at around $25-30 each, hack the guts to fit into an appropriate smaller case and provide suitable voltage to the mics, it can all run off one 9V battery, preferably lithium. It'll sound as good as the preamps you'd find in a typical Behringer/Mackie caliber board. What is the gain and the noise EIN for each of these options? Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#8
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On 14/11/2004 22:44:32, "Sugarite" wrote:
Radio Shack Boosteroo, You're just sick... That thing doesn't even qualify as a headphone amp. -- m. |
#9
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On 14/11/2004 22:44:32, "Sugarite" wrote:
Radio Shack Boosteroo, You're just sick... That thing doesn't even qualify as a headphone amp. -- m. |
#10
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On 12/11/2004 18:27:12, "normanstrong" wrote:
What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. It would be priced somewhere between $50 and $100. This is interesting: http://www.felmicamps.co.uk/ Quite a few candidates there :-) I believe I've also seen his products on an American site... -- m. |
#11
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On 12/11/2004 18:27:12, "normanstrong" wrote:
What the world needs is a cheap, battery operated stereo mike preamp with fixed gain that will goose up a condenser mike to line levels. It would be priced somewhere between $50 and $100. This is interesting: http://www.felmicamps.co.uk/ Quite a few candidates there :-) I believe I've also seen his products on an American site... -- m. |
#12
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Usenet wrote:
This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... |
#13
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Usenet wrote:
This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... |
#14
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Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I don't know what the serial resistance is, though. Low enough and it could be made to deliver levels not to far from FS line I guess. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#15
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Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I don't know what the serial resistance is, though. Low enough and it could be made to deliver levels not to far from FS line I guess. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
#16
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On 16/11/2004 05:52:48, Bob Cain wrote:
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? All excellent questions. Why don't you contact the guy and ask him, or better still, get some samples to test. Point out the potential demand (hehe!) and the benefit of publicity to sales. I reckon he knows exactly what he's doing, and some of his devices are good enough to be used by the BBC (who, of course, have different requirements to the typical punter here). -- m. |
#17
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On 16/11/2004 05:52:48, Bob Cain wrote:
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? All excellent questions. Why don't you contact the guy and ask him, or better still, get some samples to test. Point out the potential demand (hehe!) and the benefit of publicity to sales. I reckon he knows exactly what he's doing, and some of his devices are good enough to be used by the BBC (who, of course, have different requirements to the typical punter here). -- m. |
#18
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"Bob Cain" wrote in message
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. Good point. AFAIK plugin power is usually less than 2 volts with a fairly high source impedance. It's only a couple of volts. Agreed, and its usually supplied through a series resistor on the order of 1K or more. I don't know what the serial resistance is, though. It's usually designed to power a electret mic capsule. Common series resistors for those are 1K or more. Low enough and it could be made to deliver levels not to far from FS line I guess. Through the magic of micropower, rail-to-rail op amps... It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Yes, but phantom power is huge in comparison. Minimum would be 12 volts, and there will be at least a few milliamps available. This is huge compared to plugin power, especially on the voltage side. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? Check Maxim and ST web sites. Here's an interesting article about some design features of such products: http://www.maxim-ic.com/appnotes.cfm/appnote_number/741 Here's a the data sheet candidate device: http://www.st.com/stonline/books/pdf/docs/5560.pdf If so, are they at all quiet? If you call 9 uv/sqrt(hz) quiet. Probably good enough for use with electret mics. |
#19
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"Bob Cain" wrote in message
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. Good point. AFAIK plugin power is usually less than 2 volts with a fairly high source impedance. It's only a couple of volts. Agreed, and its usually supplied through a series resistor on the order of 1K or more. I don't know what the serial resistance is, though. It's usually designed to power a electret mic capsule. Common series resistors for those are 1K or more. Low enough and it could be made to deliver levels not to far from FS line I guess. Through the magic of micropower, rail-to-rail op amps... It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Yes, but phantom power is huge in comparison. Minimum would be 12 volts, and there will be at least a few milliamps available. This is huge compared to plugin power, especially on the voltage side. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? Check Maxim and ST web sites. Here's an interesting article about some design features of such products: http://www.maxim-ic.com/appnotes.cfm/appnote_number/741 Here's a the data sheet candidate device: http://www.st.com/stonline/books/pdf/docs/5560.pdf If so, are they at all quiet? If you call 9 uv/sqrt(hz) quiet. Probably good enough for use with electret mics. |
#21
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#22
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Bob Cain wrote:
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I don't know what the serial resistance is, though. Low enough and it could be made to deliver levels not to far from FS line I guess. If you don't need much dynamic range, it's possible. I had to build a think like that for an intercom system not too long ago, and it was okay for voice applications. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Phantom is easy! Phantom voltage is high enough that you can get a reasonable amount of power out of the thing. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? Lots of things will do that if you bias them real far down. They won't be very linear, but they'll be fine for voice stuff. I think that I used the classic 2N5457 switching FET since I have a box of them in my desk drawer. You can get pretty quiet if you select a good one. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#23
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Bob Cain wrote:
Kurt Albershardt wrote: Usenet wrote: This is interesting: http://www.felmicamps.co.uk/ Very interesting. Shouldn't be all that hard to hack up an MP3 player to provide plug-in power on its line input jack... These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I don't know what the serial resistance is, though. Low enough and it could be made to deliver levels not to far from FS line I guess. If you don't need much dynamic range, it's possible. I had to build a think like that for an intercom system not too long ago, and it was okay for voice applications. It's even harder to believe a phantom powered pre that could still pass on anything close to phantom levels. Phantom is easy! Phantom voltage is high enough that you can get a reasonable amount of power out of the thing. Are there any amp parts that need only a couple of volts and have quiescent currents of a few hundred microvolts? If so, are they at all quiet? Lots of things will do that if you bias them real far down. They won't be very linear, but they'll be fine for voice stuff. I think that I used the classic 2N5457 switching FET since I have a box of them in my desk drawer. You can get pretty quiet if you select a good one. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#24
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On Mon, 15 Nov 2004 21:52:50 -0800, Bob Cain
wrote: These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I recently had a need for a preamp to give 52db gain to a stereo electret mic into a Sony minidisk recorder line in. I ended up with a LM387 (old but quiet and I had one). I needed a stealth case so I used 2 mini 6v batteries. It made me wonder what sort of chip this MD, uses to enable a single AA battery to drive phones to a decent level with good fidelity as well as spin the disk and move the head. The battery seems to last forever. Frank /~ http://newmex.com/f10 @/ |
#25
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On Mon, 15 Nov 2004 21:52:50 -0800, Bob Cain
wrote: These are very cool but it's ard to believe that they can power a pre from plugin power. It's only a couple of volts. I recently had a need for a preamp to give 52db gain to a stereo electret mic into a Sony minidisk recorder line in. I ended up with a LM387 (old but quiet and I had one). I needed a stealth case so I used 2 mini 6v batteries. It made me wonder what sort of chip this MD, uses to enable a single AA battery to drive phones to a decent level with good fidelity as well as spin the disk and move the head. The battery seems to last forever. Frank /~ http://newmex.com/f10 @/ |
#26
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Hi, we make these preamps, the 3.5 Series work from plug in power. They
use very specific components in a unique design to provide 20dB of very low noise gain with low distortion. They are used extensivley by wildlife recordists who need extra gain on the mic inputs of their recorders, where of course low noise is very important. The input impedance is 10k and the output matches the mic input of the recorder. Current consumption is around 280 microamps. If I can answer any other questions about our products please do get in touch. Nick Roast. |
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