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#1
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What type mic is my P5B-E mb expecting?
I'm using this headset with the HC-6 mic element:
http://www.heilsound.com/amateur/products/proset/#1 I just tried to connect this headset to my old P5B-E motherboard and find that the mic audio level is very low. The mic works fine with my ham gear and my old R51 Thinkpad laptop, so it's working. No software adjustments will improve the audio, although I can reduce the level even more. The mic is dynamic, with a nominal impedance of 600 ohms. I don't see any mention in the manual of what sort of mic the MB expects. Is this just the wrong sort of mic, are there some jumpers or BIOS settings I've missed, or is something broken? -- St. Paul, MN |
#2
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What type mic is my P5B-E mb expecting?
Bert wrote:
I'm using this headset with the HC-6 mic element: http://www.heilsound.com/amateur/products/proset/#1 I just tried to connect this headset to my old P5B-E motherboard and find that the mic audio level is very low. The mic works fine with my ham gear and my old R51 Thinkpad laptop, so it's working. No software adjustments will improve the audio, although I can reduce the level even more. The mic is dynamic, with a nominal impedance of 600 ohms. I don't see any mention in the manual of what sort of mic the MB expects. Is this just the wrong sort of mic, are there some jumpers or BIOS settings I've missed, or is something broken? The motherboard expects something other than a moving coil microphone. Moving coil (dynamic) might be 2 to 3 mV or so. The AC'97 or HDAudio chips don't have enough gain for that, even if the 20dB boost is engaged. There is even one HDAudio chip, where some idiot "forgot" proper boost altogether (no evidence of good gain range in the datasheet - could be a datasheet error). I'm not aware of later designs repeating that error. A ceramic microphone (piezoelectric), can put out about 100mV. That should be OK. But what the motherboard is really designed for, is electret microphones. Computer audio has a DC bias voltage source (somewhere in the 3V to 5V range). The bias source connects via a limiting resistor (1K to 2K), and that is the power source for the microphone. The idea is, such a power source is not supposed to upset the other kinds of microphones. (In theory, there may be a register in the HDAudio chip to turn off the bias source, but in practice it isn't exposed so a user can do that. Older designs, like the AC'97 era, the bias source may have been external to the chip, and not under software control. Such a source might be 5V.) Even stereo microphones are handled this way, with DC bias on both left and right. So it's not like a three contact 1/8" plug has power on one pin, and microphone signal comes out on the other. In fact, on a mono microphone, the microphone end shorts left and right together, so any bias source is connected to the output signal anyway. +----------------- L-ADC | +--------- R-ADC | | Vbias | Vbias | GND | | | | | 1K | 1K | | | | | | | +---+ +---+ | | | | TIP RING SLEEVE (Jack) L-MIC R-MIC GND Now, the puzzling part, is the last time I looked in a catalog, there were some electrets that seemed to need 5V. And some of the audio chips don't have 5V as an option. Yet you don't hear a lot of complaints, which means the electrets used in computer mic/headsets must be selected to work with the lowest common denominator. There is a picture of the typical electret setup here. The DC blocking capacitor, already exists on the inputs of the HDAudio chip. (Everything on HDAudio is AC coupled.) I didn't bother to show that cap in the above ascii-art. http://en.wikipedia.org/wiki/Electret_microphone Since the Heil document I downloaded, doesn't have any technical tidbits, I can't translate what they're telling me, into anything useful. The input impedance on the motherboard, for microphone in or for line in, should be 10K ohm or greater. So not a problem when dealing with a 600 ohm source. If the microphone doesn't work when plugged into your stereo, your stereo probably won't have a bias source on it. Paul |
#3
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What type mic is my P5B-E mb expecting?
In Paul wrote:
A ceramic microphone (piezoelectric), can put out about 100mV. That should be OK. But what the motherboard is really designed for, is electret microphones. Thanks. Looks like a little change in plans is called for. -- St. Paul, MN |
#4
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What type mic is my P5B-E mb expecting?
Bert wrote:
In Paul wrote: A ceramic microphone (piezoelectric), can put out about 100mV. That should be OK. But what the motherboard is really designed for, is electret microphones. Thanks. Looks like a little change in plans is called for. I can't really be sure what kind of microphone is involved there. There seem to be too many adapters. Paul |
#5
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What type mic is my P5B-E mb expecting?
In Paul wrote:
Bert wrote: In Paul wrote: A ceramic microphone (piezoelectric), can put out about 100mV. That should be OK. But what the motherboard is really designed for, is electret microphones. Thanks. Looks like a little change in plans is called for. I can't really be sure what kind of microphone is involved there. There seem to be too many adapters. The adapters are there just to match the seemingly endless variety of microphone and headphone connectors used on various makes and models of ham radio gear. There are only two types of microphone elements, dynamic and an electret. Mine has the dynamic element. -- St. Paul, MN |
#6
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What type mic is my P5B-E mb expecting?
Bert wrote:
In Paul wrote: Bert wrote: In Paul wrote: A ceramic microphone (piezoelectric), can put out about 100mV. That should be OK. But what the motherboard is really designed for, is electret microphones. Thanks. Looks like a little change in plans is called for. I can't really be sure what kind of microphone is involved there. There seem to be too many adapters. The adapters are there just to match the seemingly endless variety of microphone and headphone connectors used on various makes and models of ham radio gear. There are only two types of microphone elements, dynamic and an electret. Mine has the dynamic element. If so (really is dynamic, moving coil), you might benefit from a separate amplifier. And picking an amplifier, isn't exactly easy. This is why, an ideal audio product, would already have a preamp built in. It might actually be easier to just switch to another microphone. If one of these boxes costs $100, it might be easier to just find an electret microphone for computer usage. http://www.m-audio.com/products/en_us/AudioBuddy.html Be aware, that even so-called "reputable" computer product makers, make crap. I have a Logitech headset with microphone, where the only way you can get audio output from the microphone, is by scratching the microphone surface with your thumbnail. It is *that* insensitive. It cannot possibly be used for voice input. My best microphone, is an Apple Plaintalk (oval shaped) one. There is an Apple microphone which is a circular disc, which is terrible. The oval shaped one has a separate 5V power supply, to run a tiny 4 pin amplifier chip inside the microphone. This won't work on a PC directly, due to the weird plug on the end. I think the 5V goes on the end contact. http://www.amazon.com/Apple-M9060Z-A...alk+microphone An Andrea Superbeam is another option. It's a stereo microphone, that with an appropriate driver, uses beamforming to do more directional recording of a mono source. Some motherboard sound drivers, used to have a provision to work with one of these. This is two electrets and stereo wiring. http://www.amazon.com/Andrea-Array-2...uperbeam+array They also sell those with a USB adapter, bypassing the computer audio path entirely, and making it a USB microphone. http://www.amazon.com/Andrea-Electro...owViewpoints=1 Paul |
#7
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What type mic is my P5B-E mb expecting?
In Paul wrote:
It might actually be easier to just switch to another microphone. If one of these boxes costs $100, it might be easier to just find an electret microphone for computer usage. Exactly so. There are lots of headsets made specifically for this application. They're cheap and easy to find. -- St. Paul, MN |
#8
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What type mic is my P5B-E mb expecting?
Bert wrote:
In Paul wrote: It might actually be easier to just switch to another microphone. If one of these boxes costs $100, it might be easier to just find an electret microphone for computer usage. Exactly so. There are lots of headsets made specifically for this application. They're cheap and easy to find. See if you can find the "Boost" tick box for Microphone and maybe there will be enough gain. They like to use creative techniques to hide this tick box from the user. https://sites.google.com/site/danlas...PAGE-large.jpg For SoundMax (and perhaps your P5B-E), it would look like this. http://img17.imageshack.us/img17/4029/mics.png Paul |
#9
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What type mic is my P5B-E mb expecting?
In Paul wrote:
See if you can find the "Boost" tick box for Microphone and maybe there will be enough gain. Tried that, wasn't enough. -- St. Paul, MN |
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