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

Subject: Re: Electret Mics on 48v (was Experience with BT-BI158's?
From: "Curt Olson" flipov411
Date: Wed Dec 12, 2007 3:16 pm ((PST))
Rob Danielson wrote:

> 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

Thank you Rob and Scott! Actually, it's $25.00 for the bare
SP-XLRM-MINI-2 adapter. $40.00 extra for the P48 mod. Still, perhaps a
wee bit tempting...

> 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

I got some help a couple years ago with a similar 9V circuit for the
Message: 183s. 
Subject: It worked fine, except it picked up some kind of interference
(not acoustical) whenever the Hi-MD mechanism dumped data to the media.

> 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.

Thank you for these links also, Rob! I came across the epanorama.net
page myself the other day, but didn't study it very deeply. I'll have
to take another peek.

Curt Olson





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