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Author Topic: battery box or 4.7 low sensitivity mod?  (Read 1083 times)

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Offline Gutbucket

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Re: battery box or 4.7 low sensitivity mod?
« Reply #15 on: January 02, 2019, 03:25:42 PM »
The most prefered option for non-balanced 3-wire electret microphones to which the 4.7kOhm mod applies is to run them the way they were designed to be run - natively in 3-wire mode rather than modified so as to work in 2-wire mode.  As far as I'm aware, this preserves the full specifications of the microphone: The higher SPL handling capability which the 4.7kOhm 2-wire mod is intended for, without the associated reduction in sensitivity and increase in self-noise as necessary trade-off.

The main reasons this arrangement is not used more frequently by tapers is that it's less convenient and less common.  The vast majority of non-balanced gear accommodes 2-wire input (signal+power, ground) microphones rather than 3-wire (power, signal, ground).  For the AT mics in native 3-wire mode this requires either AT phanom-powering adapters that provide a balanced output (some models of which can be powered by a AA battery as well as phantom), or a 3-wire battery box providing a non-balanced output.  Can't run 3-wire mode mics directly into the recorder without a 3-wire input battery box, phantom adapter, or preamp powering them.

Unlike the 4.7kOhm-mod this arrangement will not reduce the microphone's sensitivity.  Microphone output will be correspondingly hotter at any given SPL.
« Last Edit: January 02, 2019, 03:57:42 PM by Gutbucket »
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Offline Sevoflurane

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Re: battery box or 4.7 low sensitivity mod?
« Reply #16 on: January 02, 2019, 05:42:16 PM »
Now with Darktrain not doing these mods anymore, who usually does these?

Offline Humbug

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Re: battery box or 4.7 low sensitivity mod?
« Reply #17 on: January 03, 2019, 06:15:00 AM »
Hi Gutbucket, I run 3-wire AT mics. Posted a picture a couple of times of the pre-amps I use (PIPsqueak and CA9100).

My impression was that running them 3-wire reduces the sensitivity - the output is quieter (I've always presumed by 12 dB), compared to 2-wire. Of course running 2-wire without the mod causes overloaded recordings too, for amplified rock music.

This is partly why I use the pre-amps to bring up the levels again. Can you please explain in more detail?
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AT933(853C)>CA9100 / PIPsqueak>iRiver H140/Nomad JB3/iRiver H108 CF mod/Sony PCM-M10

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Offline Gutbucket

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Re: battery box or 4.7 low sensitivity mod?
« Reply #18 on: January 03, 2019, 09:13:08 AM »
Thanks for that clarification Humbug.  I really should have double checked that statement rather than simply saying "as far as I'm aware". I've not personally used any in 3-wire mode, so I don't have first hand experience with that configuration.  The only miniature AT's I currently have on hand are a pair of Darktrain modded 2-wire 853 cards but haven't actually used them.  I've used borrowed 853 and 933 pairs, both with and without the 4.7k-mod in testing low-voltage miniature-microphones in OMT arrays before moving to the DPA 4098 hypers, but all those were/are 2-wire, the DPA's being native 2-wire to begin with. 

So let me modify that statement to say that both native 3-wire mode and the 2-wire 4.7k-mod achieve increased max-SPL handling over straight 2-wire wiring, but the 4.7-mod does so at at the expense of increased self-noise.  Depending on the recording environment, that may not be an issue, but if it is then running them in native 3-wire mode avoids that issue.  Also it is the mode in which the manufacturer intended them to be run.  The downside is the inconvenience of requiring 3-wire preamps or powering modules.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

 

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