wm-61 measuring mic

nukaidee · 8th March 2009, 05:33 AM

I know these mics have been discussed for a bit before. However I was just thinking since we always measure through a laptop or computer nowadays, would it not make sense to draw power through usb? I presume usb +5VDC is pretty clean? would I get any problems if I used the usb +5VDC instead of using a 9V battery? The datasheets point out a nominal voltage of 2V to a max of 10.

Thanks!

infinia · 8th March 2009, 01:29 PM

Yes
preamp+ADC at USB will be used as well to make it practical.

nukaidee · 8th March 2009, 08:26 PM

I was hoping the built in preamp in my m-audio transit would be enough.. I don't feel like building a preamp.. mine have all failed =(. I was just going to do a 3.5mm plug and usb hybrid that will terminate in a female 3.5mm plug which is "powered" so the mic will get power..

Ron E · 8th March 2009, 09:18 PM

Well, you can just use the mic input on your sound card. That provides a 5V bias automatically. You wire the + on the mic to the tip and ring and wire the - to the sleeve, IIRC.

Dr.EM · 8th March 2009, 09:59 PM

Yes, the mic input on a computer supplies a 5v bias specifically for electret capsules (as are commonly used in PC mics).

However, regardless of how you power your mic capsule I'd strongly reccomend a good quality pre-amp to go with it. The pre-amp inbuilt on computers is usually of very poor quality, they have a lot of noise and likely distortion too; not ideal for measuring. A good quality pre-amp can be built very simply and a kit like below will make it very easy. You can then hook up to the line input which bypasses the low quality pre-amp:

http://www.madaboutsound.com/prod_de...1&sa=cf&ctid=4

I am not certain if this kit could be powered by 5v but somebody can hopefully confirm

nukaidee · 9th March 2009, 06:47 PM

well I was using my external soundcard, it is definetly better than my internal sound card, I don't have a line in anywhere so I'm out of that option, maybe I can just plug it in and see how it sounds.. can I measure the 5V by plugging in an interconnect and taking a volt meter to it?

infinia · 9th March 2009, 07:00 PM

Yes you can ...mic input is a 3 wire with a gnd, pre-in, and Vs.
What's wrong with Linkwitz preamp and capsule mods ?

nukaidee · 9th March 2009, 07:11 PM

I am using the linkwitz mod, but wasn't planning on the preamp.

454Casull · 9th March 2009, 07:54 PM

Try these threads:

Few questions about Linkwitz' mic amp circuit
http://forums.anandtech.com/messagev...&enterthread=y

infinia · 9th March 2009, 10:06 PM

Plan on a pre-amp esp if doing the capsule mod. The gain (mic fet) is cut to less than 1 for lower noise and higher spl.

8th March 2009, 05:33 AM	#1
nukaidee diyAudio Member Join Date: Nov 2008	wm-61 measuring mic I know these mics have been discussed for a bit before. However I was just thinking since we always measure through a laptop or computer nowadays, would it not make sense to draw power through usb? I presume usb +5VDC is pretty clean? would I get any problems if I used the usb +5VDC instead of using a 9V battery? The datasheets point out a nominal voltage of 2V to a max of 10. Thanks!

8th March 2009, 01:29 PM	#2
infinia diyAudio Member Join Date: May 2005 Location: Californication	Yes preamp+ADC at USB will be used as well to make it practical. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

8th March 2009, 09:18 PM	#4
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Well, you can just use the mic input on your sound card. That provides a 5V bias automatically. You wire the + on the mic to the tip and ring and wire the - to the sleeve, IIRC. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

9th March 2009, 07:00 PM	#7
infinia diyAudio Member Join Date: May 2005 Location: Californication	Yes you can ...mic input is a 3 wire with a gnd, pre-in, and Vs. What's wrong with Linkwitz preamp and capsule mods ? __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

9th March 2009, 07:54 PM	#9
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	Try these threads: Few questions about Linkwitz' mic amp circuit http://forums.anandtech.com/messagev...&enterthread=y __________________ Building a 2.1 system out of a 3/4"x4'x8' sheet


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8th March 2009, 08:26 PM	#3
nukaidee diyAudio Member Join Date: Nov 2008	I was hoping the built in preamp in my m-audio transit would be enough.. I don't feel like building a preamp.. mine have all failed =(. I was just going to do a 3.5mm plug and usb hybrid that will terminate in a female 3.5mm plug which is "powered" so the mic will get power..

8th March 2009, 09:59 PM	#5
Dr.EM diyAudio Member Join Date: Oct 2006 Location: Swindon	Yes, the mic input on a computer supplies a 5v bias specifically for electret capsules (as are commonly used in PC mics). However, regardless of how you power your mic capsule I'd strongly reccomend a good quality pre-amp to go with it. The pre-amp inbuilt on computers is usually of very poor quality, they have a lot of noise and likely distortion too; not ideal for measuring. A good quality pre-amp can be built very simply and a kit like below will make it very easy. You can then hook up to the line input which bypasses the low quality pre-amp: http://www.madaboutsound.com/prod_de...1&sa=cf&ctid=4 I am not certain if this kit could be powered by 5v but somebody can hopefully confirm

9th March 2009, 06:47 PM	#6
nukaidee diyAudio Member Join Date: Nov 2008	well I was using my external soundcard, it is definetly better than my internal sound card, I don't have a line in anywhere so I'm out of that option, maybe I can just plug it in and see how it sounds.. can I measure the 5V by plugging in an interconnect and taking a volt meter to it?

9th March 2009, 07:11 PM	#8
nukaidee diyAudio Member Join Date: Nov 2008	I am using the linkwitz mod, but wasn't planning on the preamp.

9th March 2009, 10:06 PM	#10
infinia diyAudio Member Join Date: May 2005 Location: Californication	Plan on a pre-amp esp if doing the capsule mod. The gain (mic fet) is cut to less than 1 for lower noise and higher spl. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

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