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Re: Live recording




David Wright <deblis@xxxxxxxxxxxxxxxxx> writes:

> On Thu 03 Aug 2017 at 15:43:15 (+0200), Rodolfo Medina wrote:
>> Rodolfo Medina <rodolfo.medina@xxxxxxxxx> writes:
>> 
>> > Jeremy Nicoll <jn.ml.dbn.25@xxxxxxxxxxxxxxx> writes:
>> >
>> >> On Thu, 3 Aug 2017, at 13:23, Rodolfo Medina wrote:
>> >>
>> >>> 3) mic2 is stereo.
>> >>
>> >> Not necessarily.  It might be a mono signal that's been duplicated across
>> >> two outputs.
>> 
>> Is there, as far as you know, a mono microphone model that we can be sure it
>> does not do so?  I.e., its sound is heared on only one channel?
>
> Most mono microphones will be fitted with a plug that has a tip and
> barrel, but no ring (between the two). The effects you observe could
> be no more than chance vagarities in the mechanical construction of
> plug and socket.
>
>> >> It's only 2-channel if it can record two separate sounds at the
>> >> same time.
>> >>
>> >> You can get microphones which, in a single unit, record more than one 
>> >> channel at once.  Their labelling or artwork on them normally makes it 
>> >> clear that they have L and R (or more than that) inputs.
>> >>
>> >> What makes and models are your mics?
>> >
>> >
>> > I can't tell, because they're old and I don't keep their specs.  One of
>> > them was given to me about 15 years ago, the other I don't even remember
>> > how I have it.  But I've got another teo: they are, each of them, part of
>> > a headphone.  They also let hear the recorded sound from both channels.
>> > They are:
>> >
>> >  http://www.trust.com/it/product/11916-primo-chat-headset
>> >
>> > and
>> >
>> >  http://www.trust.com/it/product/20685-mauro-headset
>> 
>> 
>> Just now I received a reply from Trust assistence and they say the mic
>> (Primo) is mono.
>> 
>> Anyway, about my example above, can we conclude that mic1 is mono and that
>> the mic input of my PC is stereo...?
>
> If you want to know whether the input is stereo, plug in a cable which
> has a stereo 3.5mm plug going to two phono plugs. (These computer↔monitor
> sound cables were everywhere at one time.) Touch just the pin of each
> phono plug in turn and see if you get mains hum separately on the
> left and right channels of the computer.

I used a cable thath has, at one end, a 3.5mm stereo male plug; and, at the
other end, a couple of twin phono RCA males.  I plugged the 3.5mm into the mic
input of the PC.  Then I did:

 $ sox -t alsa default output.wav

Then I touched alternatively one and the other of the two phone plugs and saw
that the output of sox alternatively filled up the left or right channel.


> If you're keen to use these microphones and you have the budget and
> attitude of a school pupil, buy two mono 3.5mm sockets and a twin
> phono socket unit. Solder the connections yourself using the phone
> socket pair to anchor the 3.5mm ones and give it stability. Then
> connect this device to the computer with the aforementioned cable
> and plug in the mikes.

Not very clear to me...  But I'm not good at soldering...

Many thanks,

Rodolfo