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Re: homemade mics and computer sound card

Subject: Re: homemade mics and computer sound card
From: "Rob Danielson" danielson_audio
Date: Mon May 26, 2008 8:23 am ((PDT))
At 1:19 AM -0400 5/26/08, Normand Fisher wrote:
>Hi,
>I've just build a couple of mics based on the Panasonic WM61A in
>order to record bird calls at night. Testing with my Fostex FR2-LE,
>I do get a very good signal (in fact I am surprised as to how good
>the signal is!).

Hi Normand--
I assume you are powering the WM61A's on a battery supply e.g,
perhaps: http://webpages.charter.net/tidmarsh/binmic/circuit.txt

>  However, the project would require to record for many hours and I
>would like to connect those to a computer and record to the hard
>disk.

What computer platform?

Amadeus Pro (Mac) is one sound recording/editing application that is
well-suited for long duration computer-based recording. It
automatically writes, without break, to a new file when it reaches
the file size limit (2 GB for aiff or wav). It also compiles all of
the files into one viewable and editable waveform so you can "see"
the whole night at a glance.

Maybe someone can recommend a long-duration recording application for PC.

>
>Obviously I have a problem in that the signal is so weak as to be
>totally unuseable. I realise that most computer sound card are build
>more for playback than for recording but there must be some card out
>there that have a much better mic input or a way to amplify the
>signal and feed it to the line input.

Assuming your WM61A's are battery-powered, ~$40USD device like an
iMic may do what you require:
http://www.google.com/products/catalog?q=3DGriffin+iMic+2&btnG=3DSearch+Pro=
ducts&hl=3Den&cid=3D17017937447002039085
It has a mic level input, USB connection and uses the computers
internal analog to digital conversion circuit. This would be more
than adequate for WM-61A's.

As you suggest, you'd still need a mic preamp circuit if you got an
audio card with a -10dB line input.

With an iMic, you can free your recorder other tasks without fear of
quality loss. The self-noise of the WM-61A's will mask any input
noise the iMic might introduce that your Fostex might not. Rob D.

>
>If you know a way I should go (or an area that I should pursue my
>research on), please let me know. Right now, my only option would be
>to spend the night in the field to change flash card and batteries
>in the Fostex!!! Not quite what I'd like to do.
>
>Thanks,
>
>Normand


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