Mixer
Amps:
The majority of bands start their gigging careers
with some kind of mixer amp. For smallish pubs and
clubs you'll probably only want vocals through the
main PA, so your input needs should be easy to
figure. But once you go over 100-capacity venues
you'll likely want kick drum, and possibly some
backline reinforcement, through the PA. This needs
more power and speakers that are up to the job, so
it's not as simple as just allowing a few extra
inputs.
Channel
features are usually straightforward, having either
two-band bass n' treble or three-band bass-mid-top EQ
and most have sends for internal reverb and a
monitor/foldback mix, while some add a second effects
send for use with an external unit such as delay.
How
much power you need depends on the size of the venue
and the power of the rest of your kit, but some bands
get away with 150 watts for vocals although 300 watts
is a much more realistic proposition and should cope
well with vocals in typical pubs and clubs. It's
still only 150 watts for each speaker, so chances are
they could handle a fair deal more, and 300 watts
will be fairly marginal if you want to put kick drum
and maybe some backline through the main PA.
Power
Amps:
The most important point here is about the old 4
Ohm/8 Ohm business. Power output is generally quoted
into 4 Ohms, and this is fine with mono mixer-amps,
where two 8 Ohm speakers end up as a 4 Ohm
"load". But with a stereo amp, each channel
only gets the one 8 Ohm speaker, amd power into 8
Ohms is only about 70% of that into 4 - worth bearing
in mind when figuring out how much power you really
need. Also, it's highly desirable to have some amp
power in hand - overload distortion on peaks not only
sounds nasty, but runs the risk of knackering speaker
treble units.
Almost
everyone likes their music to have deep, powerful
bass. But bass eats up amp power far more than mid
and top - this is why sub-sat systems have two or
three times as much power for the bass bins. Few bass
speakers can reproduce deep signals below about 40
Hz, but they will waste both amp power and speaker
handling, as well as messing up the sound generally.
An ultra-low-cut filter on the power amp is the best
solution, so a highly rated feature.
All PA
amps have some kind of gizmo to protect against the
seriously expensive damage that overloads can cause.
The two main types defend against short-term problems
(such as when you "short" an output with a
duff cable), and long-term heat build-up caused by
over-driving. Most amps also add some kind of
protection against the amp itself going tits-up and
attempting to deliver the National Grid to your
speakers. These are not things that many musos will
be interested in until something goes wrong and the
protection kicks in. When this happens (usually
during the soundcheck or in the middle of the second
set), the main thing is fast fault-finding and
fixing. At this time, you'll value detailed
indication of why your amp's decided to take a
siesta.
Power
amp inputs are generally on jacks/XLRs/both. XLRs are
preferable but jacks do the job acceptably well. It's
useful to have some kind of "slave" output
for adding a second amp if you move up to a bi-amped
sub-sat system (nice). Outputs may be on XLRs,
Speakons or bare-wire terminals. Bare-wire terminals
are stupidly fiddly and fragile for gigging. XLRs
work fine, but it's easy to get cables mixed up,
potentially sticking 600+ watts up your reverb unit -
not something it's likely to thank you for. Speakons
are built to handle 1000+ watts, there's minimal
chance of disastrous mis-connections and they don't
break when you drop the roadie on them.
PA
Speakers:
Budget speakers are are generally used on the
pub-club scene, playing to 100-ish audiences (less if
it's a wet Wednesday), and often handling not much
more than vocals. But when your gigs start to get a
little bigger, you'll want to be able to put bass,
drums and backline through the PA, without
necessarily shelling out for both a bigger amp and
new speakers at the same time.
Sound
quality is a key concern, and although your musical
style may effect your choice, the basic idea is that
your PA speakers should be as 'neutral' as good
hi-fi, only a mother of a sight louder. If vocals are
your only application, you may find that, as with
mikes, a speaker that's not a strong all-rounder
happens to suit your voice. Power handling and
matching to amp are a top priority in many buyers'
minds. In an ideal world, your amp would have an
'RMS' output about the same as your speaker's peak
power handling. The amp power needed starts to get
seriously expensive but, providing you don't drive
the system too hard that it constantly distorts, you
should be okay if you aim for speakers with a music
rating about the same as your amp's RMS power.
Most
PA speakers have a rather bright basic balance, and
it's fairly normal to need EQ, usually in the form of
bass boost and mid cut. Bear in mind that boosting
bass devours amp power (even a 3db lift can push your
power need from, say, 200 watts to 400), so speakers
that need a minimum of boost must be welcome. How
much sound you get depends on your speakers'
sensitivity.
See also:
