Re: recording question (mic vs. line)

[Bob Masta <audio@xxxxxxxxxxx>]

I'm not familiar with the mixer you are using, but I am very surprised
at your results.  Sound cards as a class are notorious for poor
quality on mic inputs, particularly regarding noise.  The usual advice
is "don't use the built-in Mic input; get a separate mixer".

I also note the fact that you report only the  far-field mic is having
problems.  I assume you have tried switching the mics between the
different mixer inputs, and the problem follows the mic, not the input.

Without further information to go on, I will guess that you have two
different types of mics.  The far-field is an electret mic that requires
a power source.  The near-field doesn't require it (either dynamic, or
electret with built-in battery, etc).  The mixer isn't supplying power
to the far-field.  Sound cards typically do supply power; they do this
through the connection on the stereo connector that would otherwise
be for the right channel.  (Typically 5 volts.)

If you have two identical mics and you haven't tried switching the
mics between mixer channels, then I'd guess that the mixer is
only supplying power to one the current near-field channel.

Hope this helps!


On 21 Aug 2004 at 18:40, rif wrote:

> I'm doing some speech recognition work, but my background is not in
> audio per se, and I'm running into some difficulties.
>
> I'm interested in recording speech simultaneously through two mics
> (one near- and one far-field), so that I can have paired recordings.
> My computer soundcard has a mic in, which is mono, and a line in,
> which is stereo.  My basic plan is to feed both microphones into a
> mixer (Behringer MX602A), put out a stereo line-level signal to my
> computer, record that, and separate the channels later using sox (this
> is all in linux).  While this technique works, I find that no matter
> how I seem to adjust the gains (in either the mixer or the soundcard),
> the quality I get from the far-field mic is much lower than if I
> simply plug the far-field mic directly into the mic in on the
> soundcard and record that.
>
> Is what I'm trying to do fundamentally reasonable, or am I always
> going to lose a lot of quality boosting a computer mic to line level?
> Maybe I need a soundcard with multiple mic inputs, and some relevant
> software? I said, my goal is to record from two mics simultaneously in
> a way that lets me obtain separate recordings of the same signal, but
> I don't want to lose a lot of quality with my setup.  Any suggestions
> or advice are most appreciated.
>


Bob Masta

audioATdaqartaDOTcom