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SOUND SUPPLEMENT
HEAD
CHOOSING A SOUND MIXER
INTRO
Sound mixers are amongst the simplest and cheapest video accessories, yet
they can do more to improve a video movie than almost any other post production
tool, but with so many to choose from which is the right one for you?
COPY
It's easy to forget that the soundtrack on a video movie can have just as
much, and sometimes a great deal more impact than the pictures. Newcomers to
video are frequently side-tracked by
smart-looking editors and processors, costing hundreds of pounds, without realising that, for a comparatively
modest outlay of £50 or so on an audio mixer, and a little effort, their
recordings could be totally transformed. Adding background music, sound effects
or commentary is easy; sound mixers are simple to use, and you won't need any special equipment,
just a VCR, a microphone, tape player and a little imagination!
At the moment there are over twenty five audio mixers on the market, but
if you include all the other video accessories that have built-in mixers, such
as processors and editors, the total comes to over fifty. To the casual
observer it must seem like a nightmare, with so many to choose from but if you
break the market and your own requirements down into manageable bite-sized
chunks it really isn't quite so bad. It may also help you to know that several
mixers and processors crop up under a number of different names, only the badge
and sometimes the price are different.
MONO VS STEREO
The first consideration is to decide between mono and stereo operation.
In days gone by mono mixers outnumbered stereo ones by at least two to one but
now, with the proliferation of stereo camcorders, video recorders and TVs the
situation has been reversed and you actually have to go out of your way to find
a mono mixer these days. Unless you really see no prospect whatsoever of using
or upgrading to stereo equipment, now or in the future, and you're on an
extremely tight budget it makes sense
to opt for a stereo mixer.
The next question you need to ask yourself is whether to buy a
stand-alone mixer, or kill two or more birds with one stone and invest in an
editor or processor with an audio mixing
facility built-in. The obvious problem here is cost, the cheapest stereo
mixers start at less than £30, you can
add another £30 for a mixer with basic video facilities -- an enhancer and/or fader for example -- and
£100 plus if you want special effects or editing features. There's obviously a
lot to be said for having as much as possible in one box, though bear in mind
that such an arrangement could limit your scope for expansion. It might also
meant that you'll end up duplicating some functions, as you add extra devices
to your system. One way around this is to adopt the modular approach, by
sticking with products from just one
company, such as Hama or Vivanco, who
market a range of compatible and upgradeable units.
BACK TO BASICS
The bare bones of audio mixers varies comparatively little from make to
make. The vast majority of the units you will comes across (stand-alone and
integrated) have three input channels. In most cases two of the channels have
high-impedance line inputs (typically 47-100k ohms) that are connected to the
camcorder's audio output, and the line-output of another audio components, a
cassette deck or CD player for example.
The third input has a much lower impedance (typically 0.6-1k ohms) and is
designed to be used with a microphone. It's worth noting that some mixers come
complete with their own mics, needless to say
this is very convenient, and in some cases it can be a cost saving as
well.
The connections to these devices are normally very straightforward. Most
mixers use standard phono/RCA sockets for the line audio connections, and jacks
for the microphone and headphone monitor sockets. A few models are fitted with
21-pin SCART AV connectors. They're not as versatile as phono connectors,
though they're simple enough to use, but you may also find that you have to shell out for extra leads. By the
way, some mixers come with phono lead sets, again they're worth having and may
save you a pound or two into the bargain.
ON THE LEVEL
Each input normally has it's own level control, so you can vary the ratios of
the incoming signals (original soundtrack, music from tape, commentary from the
mike, etc.); finally there is the master output level control or fader, which
sets the volume of the sound being recorded by the VCR. Other embellishments on
the more up-market mixers include level indicators; these are usually winking
LED bargraphs, though one or two use VU type moving coil meters. In most cases
they can only give the roughest
indication of over-modulation; in any event it's prudent to make a few
test recordings first, to get the feel of your system. We've only come across
one mixer so far that has any kind of tone controls, the audio bandwidth of
most video recorders precludes such niceties, though as more people upgrade to
hi-fi stereo VCRs we may find them becoming more common in the future. Pretty
well all mixers have a headphone monitor output, it's a good idea to make use
of it, rather than rely on the sound from a TV speaker; in any case you will
have to use it if you want to avoid acoustic feedback (howl round) when using
the microphone input.
Audio quality is not a major issue, over the years we've found little to
complain about. We've tried most of the mixers on the market at one time or
another and the majority appear relatively transparent to the signals passing
through them. In general battery-powered mixers give the cleanest signals; some of the units which are powered from AC
adaptors can suffer from mains hum in, some set-ups, this can be difficult to
eliminate. The slider controls used on most mixers can become noisy with use,
this can be caused or aggravated by dust and dirt getting onto the control's
resistive elements, through the slider slots, so it makes sense to keep them in
their box when not in use.
So which mixer is right for you? Our advice, if you're just starting out,
is to buy a basic stand-alone mixer and get to grips with that first; more
elaborate and expensive models won't necessarily perform any better, be any
easier to use or have any more useful facilities. If you think this might be
the start of something big then check out the modular systems, with a view to
expansion at a later date. Integrated mixers and processors are fine, but only
if you know you're going to make full use of all the facilities, otherwise save
your money.
---end---
(c) R.Maybury 1993 1703
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