AV News 195 - February 2014
More Q&A to do with mics not working
Howard Gregory
Q 'When recording with a mono mic, should it be connected to the left channel,
the right channel or both channels?' Frank
The quick and safe answer is 'both' but this is one of those simple questions
which leads to all sorts of interesting facets. The better you understand these
facets, the better your recordings will be. Whilst the principles of the explanation
apply to all recording devices, it's easiest to explain, most commonly
encountered, and of greatest importance, in the context of a computer
soundcard.
On all domestic consumer soundcards I've ever met, the audio in and out
connectors are stereo minijacks. If you set a stereo file format, then, obviously,
the signal arriving at the left input (the tip of the stereo minijack) will go to the
left channel of the audio file and the right signal (ring of stereo minijack) will go
to the right channel of the audio file. The sleeve of the minijack connection is
the screen and forms the common return path for both signals.
If you set a mono file format, then, on most soundcards, the signals from both
left and right (ie tip and ring) are added together and recorded as a mono file.
Strictly speaking half the sum of the two is written to the mono file, to avoid
overloading. This makes perfect sense - it's an easy way to convert a stereo
source to a mono file, but it opens up some pitfalls for the unwary.
If you connect a mono mic to the left channel only and set a mono file format,
then the left channel signal (mic + any background hiss etc) will be added to the
right channel signal (background hiss only.) You will have doubled the
background hiss and noise in the recorded file - and there's usually a lot of that
in the cheap and cheerful electronics on consumer soundcards.
If you connect the mic to both
channels, you get exactly the
same result whether you
record in mono or stereo. You
need a lead wired as in Fig 5
of my article in Issue 194. All
minijack mic leads that I
supply are wired to do this, for
this very reason
Q 'My mic works fine with my camcorder, but doesn't work at all when I try to
record a voice-over directly into my computer.' Mike.
The most likely cause is a powering problem, as mentioned in the article in
Issue 194. However, that wasn't the problem in Mike's case. His problem turned
out to be much more interesting, and similar to Alice's below.
Q 'When recording a voice-over, I'm using a single mic, so I assume that I
should be recording in mono. This doesn't seem to work. By accident, on
one occasion I recorded in stereo and it did work. What's going on, and
should I be recording in mono or stereo?' Alice
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