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Re: Live recording




David Christensen <dpchrist@xxxxxxxxxxxxxxxx> writes:

> On 07/28/17 12:11, Rodolfo Medina wrote:
>> According to:
>>
>>  http://www.upubuntu.com/2013/05/how-to-record-your-voice-from.html
>>
>> I record live sound via microphone just doing:
>>
>>  $ sox -t alsa default output.wav
>>
>> Now I was wondering about the stereo o non-stereo character of such a home
>> made recording...  I tried to use two microphones together, plugging them
>> together into the PC with a small common connection doubber.  Can we say the
>> result is stereo...?  I would doubt...  and how to have - if possible - a
>> stereo effect with the above basic recording instruments?
>
> Connecting two monophonic microphones in parallel with a connection splitter
> run backwards will yield a monophonic signal with reduced gain and time/
> frequency signal artifacts such as comb filtering and echo. For most
> applications, the result will not be acceptable.
>
>
> Capturing sound with two microphones can be done several ways:
>
> https://en.wikipedia.org/wiki/Stereophonic_sound#Recording_methods
>
>
> Computer microphone port(s) are typically monophonic and the line input
> port(s) are typically stereophonic.  If you want to record in stereo, you
> need to provide left and right channel signals to the line input port.
>
>
> Computer microphone ports and line input ports also expect different voltages
> and have different impedance.  I believe computer line input ports are
> designed to consumer audio equipment standards -- e.g. -10 dBV into 10 kOhm
> for 0 VU:
>
> https://en.wikipedia.org/wiki/Line_level#Nominal_levels
>
>
> (For microphone ports, my guess would be -30 dBV into 1 MOhm.)
>
>
> This means you need two microphone pre-amplifiers and/or a stereo mixer with
> two or more microphone inputs:
>
> https://en.wikipedia.org/wiki/Line_level#Line_level_in_traditional_signal_paths
>
>
> The audio capabilities of Linux have evolved over the years:
>
> https://en.wikipedia.org/wiki/Open_Sound_System
>
> https://en.wikipedia.org/wiki/Advanced_Linux_Sound_Architecture
>
>
> Sox is a command-line tool that has been around since 1991:
>
> https://en.wikipedia.org/wiki/SoX
>
>
> Audacity is my favorite interactive audio recording and editing tool:
>
> https://en.wikipedia.org/wiki/Audacity_(audio_editor)
>
>
> If you would care to explain your application, we might be able to give more
> advice.


Thanks all of you who kindly provided response.

What I want to do is recording live piano: I'd like to use two mics for that,
one on the grave and the other one on the high notes.  Besides, some times I
will need to add human voice: this requires, in my idea, a third microphone...
But even starting with two would be all right for now...  Those recordings
would not pretend to be professional, just home made for my personal tests, but
stereo.  I must say that the experiments I did with the above rude arrangement,
i.e. two mics in common Y splitter, inserted into `mic' PC entry, are not so
bad...

Thanks,

Rodolfo