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Electret Mics on 48v (was Experience with BT-BI158's?

Subject: Electret Mics on 48v (was Experience with BT-BI158's?
From: "Rob Danielson" danielson_rob
Date: Tue Dec 11, 2007 1:00 am ((PST))
At 1:03 PM +0000 12/10/07, scottsherk27 wrote:
>  > I do not think there are any low-cost, low-noise, small mics that
>>  will run on PIP.
>>
>>  As the Sony PCM-D50 only has a PIP external mic input and the
>  >Fostex FR2-LE only has 48 volt phantom inputs, perhaps we should dig-up
>  >the simple mods allowing electret mics tp run on 48v. For low-profile,
>  > stereo imaging and other flexibiilities, I'd much rather have
>>  head-wearable EM-158's or WL-183's than X-Y recorded mounted
>  > electrets. Rob D.
>
>For the record: I've been using my EM-23's with my Fostex FR2-LE
>very successfully. I use the Sound Professionals Phantom Power
>Adapter which is currently on sale for $25!
>
><http://www.soundprofessionals.com/cgi-bin/gold/item/SP-XLRM-MINI-2>http://www.soundprofessionals.com/cgi-bin/gold/item/SP-XLRM-MINI-2
>
>Very clean sound.
>
>Scott Sherk

Thanks Scott! Sounds like Sound Pro's SP-XLRM-MINI-2 adapter cable 
might use 47K ohm resistors on #2 pins of the XLR connectors with 
pins 1 & 3 "tied."  If it work acceptably with 183's and other 
electrets, its a very simple mod. $25 is hard to beat, too.  Perhaps 
you can see a resistor in each XLR connector, perhaps yellow, violet, 
orange,.. 
http://www.electronics-lab.com/articles/basics/theory/resistor_codes.htm


At 8:44 AM -0600 12/10/07, Curt Olson wrote:
>
>Rob, is there a chance you can point us to such a mod?

The MicBuilders list would be a good resource for this. The article 
on DIY WM-61A electret capsules in Tape OP years ago used a 9 volt 
battery and provided XLR connections. This circuit is larger profile 
than many might prefer and is not specifically for 183's.  The 
article used to be available through ProSoundWeb.com. Here's a 
variation 
http://www.christianmusicweb.com/microphones/mic_project.html

More generically for electret capsules,Tomi Engdahl  has provided a 
few circuits:
http://www.epanorama.net/circuits/microphone_powering.html#phantom

I'm not sure what the latest wisdom on the best circuit is and if the 
183 capsules differ somehow. I guess one could A/B compare the 
options including the MX-183 and a P-XLRM-MINI-2.  Rob D.





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