| PA Proverbs
(Hints and Tips)
A collection of short hints, tips and other PA wisdom shared
to assist you in your use of PA systems. If you have any such
advice or comments of your own that you would like to submit
for possible inclusion on this page, please
(or put your suggestion in a comment on the
associated with this site).
Minor alterations may be made to accepted contributions,
to suit the general style of this site.
Contributors will not be identified on this page unless they
request to be. Many thanks to all our contributors.
Please note that some items on this page do not fall neatly
into the section headings, so you might want to look at two or more
sections. For example, tips about the connection of a cable to a
microphone might be found under 'Cables', 'Microphones' or
'System Assembly and Interconnection'. (If anyone can think of
a better way to organise them, please let me know!)
My apologies if you are offended by the seemingly obvious nature
of some of the items. However, it can be useful to be reminded even
of the obvious, and some less experienced engineers than yourself
might find them them helpful! Please remember that these 'proverbs'
are just opinions on what is (or is not) good or useful practice.
They may need adaptation to specific circumstances, and other
opinions may differ.
"What really gets me into trouble is not what I don't
know, it's what I know for sure, but just isn't so."
− Mark Twain.
- Never just assume that anything is going to
operate as it should at the moment it's needed, without
having checked it first. Equipment goes faulty, cables
get connected incorrectly, controls get misadjusted.
Always test everything, well before the
event starts, to give plenty of time for correcting
(or working around) any problems you find.
[See Rig check,
Line check and
- Once equipment is unpacked, and especially during an
event, keep all food and drink well clear of it − and
make sure everyone else does too. This is especially
important for equipment such as mixers and
that have lots of sockets and/or slots
for slider controls. Anything that gets into these is
sure to cause problems sooner or later.
- The better packed your equipment is, the less likely it
will be to get damaged during transit. Good quality
flight cases are expensive, but so are repairs − and
- To help keep on good terms with hire companies, always
normalise their equipment
before returning it to them.
- When cleaning CDs, always wipe in straight lines from the
centre outwards (this minimises the effect of any minor
abrasion caused by the cleaning). And if cleaning to try
to correct a problem with a particular track, remember that
track number 1 is the innermost track on the disc.
- Remember that most types of silver-coloured
gaffer tape incorporate
an electrically conductive
layer (made of aluminium). When used to secure cables, in some
cases this layer may increase the pick-up of interference
by the cables or may increase unwanted
coupling between adjacent cables. Therefore, it's best not
to use the silver-coloured type on cables except where essential
for aesthetic reasons. But in any case, never use it on or near to
exposed connections of any kind. [No colour of gaffer tape
is suitable for use as an insulating
tape, so must never be applied directly to exposed electrical
connections or conductors. Where an insulating tape is required,
use only suitable purpose-made tapes (e.g.
PVC tape, where suitable)
- Maintain all equipment in good condition. In particular,
regularly check cables for damage and check equipment
dust filters and cooling fans for any build-up of dust.
Back to top.
(Also see the Microphones
- Always use the appropriate kind of mic for the job
(see the microphone
- After speakers, this is the part of the system that
will make the most difference, in terms of sound quality,
so don't compromise. In general, avoid budget types.
Only use high-impedance
types if essential − they require suitable
connection arrangements to avoid sound quality
- Although capable of a better quality sound,
condenser mics can
be more prone to damage by rough handling. So for rough
stage vocals use, use a rugged good quality
such as the Shure SM58, and only use condenser mics where
really necessary, such as for drum kit
- To avoid the embarrassment of flat batteries, use
condenser mics and DI boxes
rather than battery-powered ones. (Some are capable of
being powered either way.)
- Don't test mics by blowing into them or tapping them, as
this can cause damage. Speak or sing into them instead.
The spoken words "one", "two",
"check" are 'tried and tested' words to use.
When adjusting the mic channel
listen to "one" to adjust the
"two" and/or "test" to adjust the
treble, and "check"
to adjust the mid-range
frequencies. Alternatively, if a mic needs to be checked
during an event and speaking into it would be
inappropriate, lightly scratch the
basket of the mic with a
- When using multiple hand-held
or if wired mics
need to be moved around on the stage (or are liable to be
taken off their stands and replaced on different ones by
vocalists!), identify each mic with a
different colour of self-adhesive tape − stick
a piece of the same coloured tape against the relevant
fader of the mixer,
so you can readily keep track of which fader controls
which mic. Wrap a band of the tape
around both ends of the held part of the mic, as
either end may be at some time obscured by the performer's
- Encourage performers in correct
as holding the mic at an appropriate distance for the
particular use, and at the correct height and angle.
(However, don't forget the visual aspect − there's little
more frustrating to an audience than never being able to see
the performer's lips, even if the sound is superb −
especially when close-up video is in use.)
- Try to discourage vocalists from wrapping their fingers
around the basket of the
microphone, as obstructing the entry of sound into part
of the microphone can significantly alter its directional
characteristics and may make
feedback more likely and/or
- Try to discourage vocalists from holding radio mics at
the very bottom end, in the case of types that have a
projecting aerial there, as this would reduce the
effective power of the transmitted radio signal, and
so increase the likelihood of reception problems.
- If possible, avoid using wired mics that have on/off switches.
Some performers have a habit of switching them off accidentally
(or deliberately and then forgetting they've done so), or
leaving a mic switched off for a later performer who expects
to find it switched on. If you do need to use mics with
readily accessible switches and these mics will be
handled by performers, or their switches might be accidentally
knocked, then put some suitable tape over the switches
to avoid accidental operation.
- Correct placement of mics is often critical to achieving
the best results, especially when close-miking acoustic
instruments. When deciding where to place a mic, it's
worth considering that
the mic will 'hear' much the same sound as if you placed
your ear in that position, pointing in the same direction.
(But only try this if the sound level at that position
isn't so high as to risk damaging your hearing.)
- When miking-up a
cab, listen to the cab first
to check that the driver you choose
to mike-up isn't a dodgy-sounding one. (Again, beware of
high sound levels − they may occur suddenly.)
- When a mic is used with a tight-fitting mic clip,
be aware that the pressure of the clip can cause the
XLR latch to be released as
the mic is removed from its stand by the performer, with
the possibility that the XLR plug can then lose electrical
connection with the mic, or even fall out completely.
If this looks a
possibility, be sure to place the mic into the clip with the
XLR latch-release button in line with the slot of the clip,
and ensure that the performer knows to replace the mic
- Inferior quality windshields
can seriously damage your sound!
- When using condenser mics with phantom powering, check
that the voltage of the available phantom power (48V from
nearly all modern PA mixers and mic pre-amps) is correct
for your microphones before connecting them. Most condenser
mics intended for use on stage are designed for 48V powering
but you unless you are certain it is still wise to check.
- When using several condenser mics and/or
DI boxes with
phantom powering, check that the the total current demand
of all the phantom-powered devices connected to the mixer
does not exceed the total phantom power current available
from the mixer.
- If using a
it is best to avoid applying phantom power to it
if at all possible, as a fault in the mic cable
can easily cause the mic to be seriously damaged.
- When using a ribbon mic, never blow into the mic,
as this is almost certain to cause serious damage to
- If a mic is suspected of being faulty, don't put it back
in the box with the others, to be taken out again and be
used another time. Put it separately (preferably marked in
some obvious way) until it has been checked and repaired.
- When attaching a lavalier
mic to its user's clothing, get them to tilt their head
fully forwards and ideally clip the mic at a height
about 2 cm (1 inch) below the point on
their chest where their chin
touches it. If the user is to be facing forwards for the
majority of the time, then preferably clip it at a central
If the user is to be predominantly facing towards one side
(as in some interview situations), then clip the mic
at that side of centre.
- If a new mic has to added, or a faulty one replaced, during
a performance, it is often inappropriate for it to be tested
in the normal way, by someone speaking into it. Even if the
mic is not routed to FOH
during the test, seeing a person speak into it can be a
In such cases the basic operation of the mic can be confirmed
by activating the PFL on the
relevant channel, turning up the headphones level control,
and listening for the
picked up by the mic.
(It may also be necessary to temporarily turn up the channel
gain control, depending upon the sound level in the
vicinity of the mic.) The only problem with this is that it
doesn't confirm that you really are listening to the new mic
(it may have been plugged into the wrong channel on the
So if the mic is being placed by someone other than
yourself, a better approach is to have them lightly
scratch the basket of the mic with a fingernail, while
you listen for this distinctive sound via the channel
PFL. The assistant can be given a 'thumbs up' signal
when this check is completed.
- If a performer insists on swinging a mic on its cable,
do not rely on the latch of the XLR connector to secure
the mic to its cable. Use only a heavy-duty mic cable in
good condition, and check the tightness of the XLR's cable
clamp. Wrap plenty of
gaffer tape around the
mic, the connector and at least the first 150 mm (6")
of cable (taking care not to tape over the
XLR latch release button!). Also, to help ensure that there
is no possibility of the mic or its cable striking another
performer, crew personnel, or object, securely attach some
coloured tape to the cable to indicate the furthest distance
from the mic that the cable can be safely held by the
performer, when swinging it.
- When using microphones some distance from the sound source
(for example in the case of drum kit overheads, choir mics
or rifle mics), and
monitor speakers are in use, take care to avoid the
sound from those speakers being picked-up by the mics
along with the wanted sound, as that can degrade the
This can be a particular
problem with drum kit overheads, because most dummers
like their monitors loud. Consider using headphones or
Otherwise, minimise problems by using positioning and
directionality of both the
mic(s) and the
and keep the monitor(s) levels
down to the minimum acceptable.
- When an acoustic guitar doesn't have a built-in pickup,
close-up use of a stand-mounted microphone is best avoided
if the guitarist is standing, because even slight
movement of the guitar body relative to the mic can
significantly affect the nature of the picked-up sound
(as well as its level). In a live situation when
close-miking of a guitar is required, the guitarist
should be seated (and should take care to hold the guitar
in a fixed position) or else a miniature
gooseneck mic, or
a suitable temporary pick-up, should be attached to
the guitar. (In a studio recording situation, use of a
stand-mounted mic may be suitable if it can be placed
at a sufficient distance from the guitar to make any small
changes in position and distance less significant.)
- Be sure to adequately tighten mic stand boom adjustments,
to avoid unintended changes in position or height.
Tightness is particularly important when a heavy mic
is used with a boom covering a horizontal distance
of more than 45cm (1ft 6in), in order to avoid a gradual
sagging in height due to the weight of the mic.
- When a vocalist is to sing into a mic on a stand, be sure
to set the height of the stand correctly. An incorrect
height may cause the vocalist to stoop or to stretch,
neither of which is helpful for good vocal technique.
Back to top.
Other On-stage Issues
- Ensure that all guitarists and other musicians with
hand-held intruments that connect to on-stage equipment
the PA system using an
connection (usually a
are aware of the need to avoid creating the
loud impulsive noises that can result from plugging-in or
unplugging instrument cables (at the instrument end), as
these noises can be seriously damaging to equipment and very
unpleasant for audiences.
Turning down the volume control
on the instrument will never be effective in preventing
these noises. [They usually originate mostly from the
of the plug unavoidably contacting the
sleeve of the
instrument's jack socket as the plug enters/exits, and in
the case of instruments equipped with a battery-powered
pre-amp, from the
switching on/off of the battery
by insertion/removal of the plug.
jack plugs can sometimes be helpful in avoiding these
problems, but are not always effective.]
When the instrument is amplified by the PA system,
the sound engineer
the relevant channel(s)
on the mixer, before
the instrument is unplugged, and there needs to be a
pre-arranged cue for the
sound engineer to do that. Muting at the mixer
in this way will avoid unpleasant noises from the PA system
and will protect them from possible damage.
However, if the instrument has a connection to
then the only way to protect and avoid the noise from
that equipment is for the musician to
either turn down their amplifier or to interrupt the signal
to it, before unplugging the cable from their instrument.
Interrupting the signal can often be conveniently achieved
by use of an appropriate pedal,
or by unplugging the instrument cable at the non-instrument
end before unplugging it from the instrument.
As a last resort, the noise created by unplugging from
the instrument can sometimes be significantly reduced
if the musician first grasps an earthed metal part of the
jack plug (i.e. a part that connects with the sleeve
of the plug) and then touch the metal sleeve or nut of the
instrument's jack socket with a finger of
that hand, maintaining contact until the plug is fully
in or out and taking care not to touch the tip of the plug.
If the instrument socket has no touchable metal parts
(e.g. is recessed),
then instead of touching the socket with a finger
use the other hand to touch an earthed metal part of
the instrument (e.g. the pick-ups).
- It can be helpful in keeping stage sound levels under control
if, when asking band members if they can adequately hear
what they need to, they are also asked if there is anything
that is swamping what they need to hear and would be usefully
reduced in level.
- When giving advice to band members, e.g. on
technique, it can be useful to remember that people often
find it easier to keep in mind something to aim for
rather than something to avoid. For example, it will
often be more effective to say "It would
be helpful if you could hold the mic closer to your mouth",
rather than "It would be helpful if you didn't hold the mic
so far from your mouth".
- It's worth giving some serious thought to the type and brand
of batteries that you use in your radio mics and in
beltpacks for body-worn
mics, wireless instrument systems and
especially if operation for several hours between battery
changes is a requirement. Zinc types are best avoided.
A useful comparison of many AA-sized alkaline (and a few lithium)
UK brands can be found at
System manufacturers generally recommend avoiding the use of
rechargeable types − mostly because their life between
recharges is quite limited and reduces unpredictably as
the battery ages. To be sure of avoiding battery failure,
many professional users use a new set of alkaline batteries
for every show. But in less
critical applications where budget is tight and where each use
is shorter than around 1.5 hours, with plenty of time for
recharging in between, using good-quality rechargeable types
can be very convenient and cost-effective.
Back to top.
System Assembly and Interconnection
(Also see the
System Assembly page.)
- When deciding on the location of the
mixer, don't assume that a position on the centre-line of
the venue will give the best listening position.
Although this is often the best choice,
sometimes sound reflections from surfaces (especially curved
ceilings) can cause problematic cancellations at a
central position, so a position slightly to one side
may be preferable in such circumstances.
- For rapid location of a desired channel during an event,
when cabling-up the system assign the stage
signal sources to the mixer channels in the same order that
they are positioned across the stage (as viewed from the mixing
position). As it's usually helpful to keep the channels used
for vocals next to each other, assign those channels (in stage
position order) first, followed by the instrument channels
(in stage position order). [Or, use a standard ordering such
as the one shown here
- To avoid dangerous and/or expensive mistakes, don't use the
same kind of connectors for
different purposes in the same system. In particular,
beware of multiple uses for
amp-to-speaker connections) and for
XLRs (balanced audio lines or
low-power amp-to-speaker connections). This is especially
important for touring systems, and even more so when
unskilled people are assisting in assembling the rig.
(If such mixed use of connectors is unavoidable,
ensure that all
the relevant connectors are very clearly labelled.)
- If it is desired to extract a
line level signal from one
or more individual channels of a mixer, e.g. to
for individual performers, or for multi-track recording
purposes, and there is no
'direct out' facility,
you can use the channel
'insert' facility of your
mixer (if it has that!). For each channel of
interest, you need to make (or otherwise obtain) a special
cable, consisting of an
terminated in a
jack plug. The screen of
the cable is connected to the sleeve of the plug
(as usual) but the 'signal' (hot)
conductor is connected to both
the tip and the ring of the plug. This plug then
connects into the 'Insert' socket on the relevant mixer
channel; the link between tip and ring connections prevents
the signal path through the mixer from being broken.
The other end of the cable is terminated normally in
whatever kind of connector is needed for the equipment you
are feeding the signal into.
The internal wiring of the 'Insert' socket on some mixers
supposedly avoids the need for such a special cable,
allowing a signal to be extracted by inserting an ordinary
2-pole ("mono") jack plug
only partially into the socket − just to the first 'click'.
However, this is not recommended because in a large system
it would be too easy to forget which plugs are deliberately
partially inserted − it would be all too likely (especially
for some other 'helpful' soul) to think that the plug had not
been properly inserted, or had subsequently taken a tug on
its cable, and push it fully in. The consequences would not
- Most tape, CD, and DAT recorders
reproduce their input signals on their output connections
when in record mode. Therefore, when such a machine is
connected to a mixer for both recording and playback,
there is a likelihood of an electrical feedback loop
being created which can seriously damage speakers, etc.
So unless you are sure your machine does not have this
facility, or has a foolproof way of disabling it, always use
the designated 'playback' inputs on the mixer (which
usually do not feed to the 'record' outputs −
but do check this!), rather than using
normal channel inputs. (Alternatively, use an auxiliary
output on the mixer, rather than the 'record' output, and
be very careful not to turn up that Aux Send on the
used for playback. For a mix the same as the main mix, use a
post-fade auxiliary and set all the required Aux Sends to
3 o'clock − or to
'0 dB' if marked.)
- Be aware that most mixing desks do not isolate the XLR (mic)
input of a channel when a jack is inserted into the channel's
line input. So it's always best to ensure that there is no plug
in the XLR input when the line input is being used, to
avoid the possibility of interference with the line-level
signal caused by connections made to the other end of any XLR
cable that usually plugs into that channel. (Such connections,
e.g. to an usused DI box,
may be more easily overlooked or accidentally made
if the XLR cable is routed from a stagebox.) [Of course, the
converse also applies: don't have anything plugged into the
line input if using that channel's XLR input − Ed.]
- To assist in balancing Left and Right speaker levels, use the
same length of speaker cable for both Left and Right speakers
− even when the Left and Right amplifiers are located
together and closer to one side than the other. (But don't
have the unused speaker cable length coiled on a reel, as
this may impair its ability to lose heat and so cause
- Consider using a 2-channel amplifier configuration, with
separate 'Left' and 'Right' connections from the mixer,
even when you're mixing in mono. That way, if an amplifier
fault or an amplifier feed fault develops during an event,
you'll probably only lose half of the system rather than
all of it.
- When not a safety hazard or too unsightly,
coil any excess length of stage cables at the
source (e.g. mic) end of the cable.
This avoids the stagebox area
being cluttered-up with all the spare cable (which can make
later access difficult) and makes those last-minute changes
of mic location much easier to cope with − especially when
the cable run to the stagebox has been taped down. If for some
reason the coils can't be at the source ends,
make them a metre or so away from the stagebox − and use
a releaseable cable tie around each coil to prevent them
- When connecting any unbalanced
source (e.g. most instruments, iPADs®, notebooks,
etc.), to a balanced
mic input of a mixer or
always use a DI box.
Don't be tempted to use an in-line adaptor to convert from an
unbalanced jack to an XLR, as these don't provide a
balanced signal to the
mixer and can cause serious damage to the source equipment
if the mixer has
- Not all balanced outputs are designed to cope with phantom
power being applied to them. For example, when linking a
mixer's balanced outputs to another mixer's mic inputs
(cascading), to avoid
possible serious damage be very sure that phantom power
isn't activated on those input channels before making the
connections. To be certain of avoiding damage (e.g.
if phantom power were accidentally activated later), use a
in each feed. (If possible,
it's always best to have phantom power deactivated on channels
where it's not needed, even when using source equipment
that is designed to cope with it.)
- When connecting balanced outputs to unbalanced inputs,
or connecting to them using unbalanced cable, check the
manufacturer's instructions for the source equipment,
on how to make such a connection. If making such a connection
from a balanced output of the
it is important to link the unused
of the output with
signal earth, in
order to avoid the possibility of relatively high levels
of noise being added by the
- If your speaker cables have jack plugs at the end that
connects to the speakers, don't plug-in or unplug the jack
at the speaker end while the other end of the cable is
connected to an amplifier
that is switched on. (As the plug goes in or out, the sleeve
contact inside the socket could bridge across the insulation
between the sleeve and tip of the plug,
the amplifier output and damaging the amplifier.)
In any case, it is not recommended to connect or disconnect
speakers from amplifiers that are switched on. − Also
see the next tip.
- Unless your speaker cables have connectors with
protected contacts (such as
Speakons) at the
speaker end, don't leave that end of
the cable unplugged while the other end of the cable is
connected to an amplifier that is switched on. (The
'signal +' (hot)
pole of the plug could make
accidental contact with earthed metalwork,
short-circuiting the amplifier output and damaging the
amplifier. And, in powerful systems, touching that pole
could be an electric shock hazard.) −
Also see the previous tip.
- Preferably, avoid connecting speaker outputs of
backline amplifiers to DI boxes.
(Instead, use a mic on the speaker, and/or use a line-level
output into a DI box.) If you must do this, only use a DI box
that has a specifically-designated speaker input, only use
a passive DI box, use a
correctly-wired speaker cable to make the interconnection
and take great care to make sure that the DI box's
earth lift switch is in
the 'LIFT' position before you connect the
amplifier to it.
[Also see the previous two proverbs, and see
output − Ed.]
- If you are faced with a
backline amp that has an
intermittent or crackly output, first check if it has
jack connectors that are not
being used. It's a frequent problem on older amps that the
internal switch contacts on these connectors, that complete the
signal path when no plugs
are inserted into them, fail to make good electrical contact.
Sometimes putting a plug rapidly in and out of the relevant
connector (usually the Return − but sometimes the Send!)
lots of times will clean the contacts sufficiently to
provide an adequate short-term fix,
but a much more reliable quick solution is to use a short
to link the Send and Return connectors.
- When assembling large systems, keep an eye on mains power
requirements. As a rough guide, amplifiers providing
a total of 2 kW
output power is the maximum that should be supplied through
any one 13 Amp socket outlet of the building's fixed
- When connecting several speakers to one channel of an
amplifer, take care not to go below the minimum
catered for by that particular model of amplifier.
- When connecting an unbalanced XLR output of a mixer to
an unbalanced XLR input of an amplifier, be aware that
equipment differs in which pin of the connector is used
as the 'hot' connection. Most British equipment uses
pin 2 for the 'hot', but some older US equipment uses
So, if these types of equipment are being interconnected
a special cable will be needed to make it work.
N.B. Pin 1 is always used as the 'earthy'
- When connecting a mic cable to a microphone, be sure that
the XLR is pushed in hard enough for the latch to click
into place (greater pressure is needed for XLRs having a
rubber sealing ring). This is especially important if the
mic is to be removed from its stand by the performer, and/or
is likely to be treated roughly. Plugs falling out of mics
during a performance is not good news.
- When running out audio XLR-to-XLR cables such as mic cables or
feeds to amplifiers, it can be helpful to remember that the
pins of the connectors 'point' in the direction of the
signal flow. So, the end of the cable with a female
connector needs to be at the 'source' end of the run, and
the end with a male connector at the 'destination' end.
N.B. DMX lighting control
cables are the opposite to this!
- When running out an
cable, avoid including the stage within the area of the
loop if at all possible. This will reduce the likelihood
of magnetic feedback problems caused by guitar pick-ups
etc. picking up the field from the loop.
(Note, however, that the field is not contained
entirely inside the loop area − there is some
degree of 'overspill' − so the further the loop area from
the stage the better.)
- Wrapping a mic cable a couple of turns around the
vertical pole and boom arm of a mic stand is a good
way to keep the cable tidily in place (when your stand
isn't supplied with the nice clips for that purpose).
However, don't do this (still less use the nice clips!)
on a vocal mic stand unless you're sure that the
vocalist will not want to remove the mic from its stand
and hold it, at some point during the performance.
- When a stereo source is to be connected to a stereo rig,
the ideal would be to use a fully-featured stereo input
channel on the mixer. However, many professional mixers
do not have these (e.g. so-called 'Tape/CD' inputs
often have very limited EQ and Aux Send facilities).
In such cases it may be necessary to use two normal mono
channels of the mixer, one for the Left signal (panned
hard left) and one for the Right signal (panned
hard right). When doing this it is necessary to ensure
that the channels are set-up identically, and that any
subsequent adjustments are made to both of them.
- When a stereo source is to be connected to a mono rig,
it is necessary to decide whether or not the Left and
Right signals must be
summed, or if just one of
them can be used. For recorded material, the signals
must usually be summed in order to avoid losing content
(in case of any
in the recorded mix), but for stereo instruments often
just the Left channel is used. (Many stereo keyboards
provide a summed mono output from the Left output jack
if the Right output jack is not used − but some
musicians might query the lack of two cables...)
If summing is required, then if the mixer has
an available stereo input with sufficient features this
may be used provided that the relevant
Left and Right busses get summed at some point into
the mono signal that is used
(e.g. by these busses being routed
to the same Mono output of the mixer).
If a suitable stereo input is not available then
a 'Y-splitter' may be used 'in reverse' to combine the
source's Left and Right output signals by direct
connection of both of them to a
single mono channel of the mixer. However, do not
do this if the signals come from a very
(such as a headphone output) − otherwise there
would be a risk of distortion or even possible damage
to the equipment, due to current overload.
There is not usually any problem
in making a direct connection between line-level Left and
Right outputs of semi-professional or
consumer-type CD decks
If there is any doubt about the suitabililty of
directly connecting Left and Right together,
then it is necessary to
use two mono channels of the mixer, one for the Left
signal and one for the Right. The two channels must be
set-up identically (routing both to the same bus), and
any subsequent adjustments must be made identically
to both of them.
- Problems (typically intermittent operation, or distortion)
are sometimes experienced on particular mixer channels,
due to oxidation of the normalling contacts of the
Insert jack sockets. (This is more likely to occur if
the contacts have been held separated for a very long
period of time, by a plug remaining inserted.)
Until the socket is replaced, the problem can be solved
by use of an insert lead with its 'send' and 'return'
connectors at the far end linked together, or by use
of a 3-pole jack with its tip and ring terminals
connected together (and no cable attached).
- When connecting or disconnecting to/from
a live 3-phase supply (for example by inserting or
removing a 4-pole CEE-form
connector), there is a possibility that the
connections of two or more of the phases may momentarily
make contact without the Neutral connection.
This could potentially result in serious damage to any
equipment currently connected to the distribution arrangement
that is being connected or disconnected. Therefore, it is
strongly recommended that all equipment is isolated from the
distribution arrangement (e.g. by removing their plugs)
before connecting or disconnecting the arrangement to/from
a live 3-phase supply. (It is not sufficient to merely ensure
that the equipment switches are in the Off position.)
- When using equipment that requires an external
power supply unit,
use only the make and model of unit advised by the equipment
manufacturer. [For an explanation of this advice, see
this question on the
FAQ page − Ed.]
Back to top.
(Also see the Intro for Mixing
Engineers page and the Mixing
- Always set the channel gain
controls first, using the mixer's built-in
indicators. Note, however, that a subsequent large change
to the channel EQ
settings will often change the overall level of the
signal. If an EQ boost
significantly increases the level, it may be necessary
to decrease the setting of the channel gain control
in order to restore the required
headroom (which in turn
may necessitate re-adjustment of the channel fader).
- After the initial
rig check, set up
monitor mixes before the
front-of-house mix, as this enables the total on-stage
sound level to be assessed and controlled early on.
Also, when the band are desperate to start their rehearsal
(because of delays to the set-up schedule, or because
insufficient time has been scheduled for a rehearsal
after the sound-check),
having the monitors set up first will enable the band
to start rehearsing sooner.
- It is common for vocalists to sing louder, and for
musicians to play louder, when the audience are in place
for the event (as compared to how they performed in
the sound-check). So it can be helpful to set the gain
controls a little on the low side during the sound-check,
to accommodate the higher levels expected later.
- It can sometimes be difficult to see which switch-buttons on
a mixer are 'In' and which are 'Out' − especially in
poor lighting conditions. To help with this, some mixers
(e.g. Mackie) have a line drawn around the buttons
(e.g. a white line on grey buttons). If you can see
the line above the mixer panel then the button is 'Out';
if you can't then it's 'In'.
- To avoid overloading
the mixing amp of the desk, when creating mixes start with
the faders at their '−5dB' positions (approx 60% of
travel), then vary them from there − mostly with
reductions. If during sound-check you end up with
any channel faders
exeeeding '+3 dB' (85% of travel), more than 10% of them
exceeding '0 dB' (75% of travel) or more than a quarter
of them exceeding '−5 dB', then increase the main
fader setting and back off all the channel faders by a
corresponding amount. (See also the next proverb.)
- To maintain a satisfactory
ratio from the the mixing amp of the desk, if during
sound-check you end up with all the channel faders
at below '−15 dB' (approx 30% of travel), then decrease
the main fader setting and increase all the channel faders
by a corresponding amount.
- Only mix in stereo when there's a real benefit
(e.g. special effects) − and only when
the layout of the venue is such that
the majority of the audience are covered well by both the
Left and Right speakers (this is very rare!).
- Make good use of your mixer's
(e.g. vocals in one group, drum mics in another,
guitars in another, etc.),
so that the level of these sets of channels in the mix
can be adjusted as a whole, using the group faders.
If your mixer doesn't have a grouping facility, but has Left,
Right and Mono (L+R) master faders, then by panning the
vocals to hard left and the instruments to hard right you
can use the Left and Right master faders as group faders
(in which case of course you use only the Mono output to
- The sound throughout a venue will be different at different
locations − and not just louder nearest to the speaker
What's more, the sound will often change significantly when
the audience enters − there will be less natural
the high frequencies will tend to be reduced towards the
back of the venue as they are absorbed much more by the
audience than are the bass frequencies
(see grazing effect).
So familiarise yourself with the sound in different parts of
the audience area, and during the event be aware that
members of the audience are not all hearing the same sound
as you − especially if you are mixing from the very
back of the venue.
- When setting the individual channel EQs during
sound-check, it can help you to focus on the sound
via the channel to be adjusted if you
first temporarily raise the level of that channel in the
mix. After setting the EQ, restore the channel fader to
its correct position (which may be slightly different to
its previous position, because of the effect of the changed
EQ) before moving on to the next channel.
- One possible way to set
controls is as follows:
- After setting the Low (LF or
Bass) and High
(HF or Treble) controls
as required, make sure that the cut/boost
the sweep EQ is set flat
(i.e. to '0',
- Now listen to the sound and decide what you don't
like about it most of all.
- Next set the cut/boost control of the sweep EQ to
give a large amount of
boost (about 10 to
12 dB) and
set the Q control (if you have
one) to about 2.5.
- Set the Frequency control to minimum, then slowly
rotate it up to its maximum setting, noting the position
that makes what you don't like about the sound (as noted
above) become significantly worse. When you have
swept the whole range, return the Frequency control
to that position, and return the cut/boost control to '0'
(flat), so that the original sound is obtained.
- Now slowly rotate the cut/boost control anti-clockwise
until the best sound is obtained, in conjunction with
adjustments to the Q control (if you have one).
- Finally, make any necessary re-adjustments to the
High and Low controls (and to other sweep EQ controls
on that channel, if it has any others).
- If you have other sweep EQ controls on that channel,
proceed to adjust them in like manner.
- When using a multi-amped system
(i.e. separate amplifiers for
each frequency range, e.g. bass, mid, high),
keep the main
flat until the
have been properly set and the amplifier levels
for each range have been properly balanced.
- When graphic equaliser sliders
have a very small travel
(35 mm or less), an adjustment
of just one or two mm can have a very significant effect
on the sound. Check the 'Range' setting, if there is one
(e.g. ±6 dB or ±12 dB).
- Remember that the FOH graphic
equaliser affects the total mix, so don't be tempted
to adjust it based on the sound of a single source.
(The exception is playback of a pre-recorded track
that you are very familiar with the correct sound of
− in which case first be sure that the relevant channel
EQ is set flat!) An ideal way to set up an FOH graphic
is using pre-recorded test tracks corresponding to
each frequency band of the graphic, and checking the sound
level of each band at several places in the venue using a good
quality sound level meter (this takes a long time!) −
Again, first be sure that the EQ is set flat on the channel used
for playing the test tracks! [Analysis tools are now a popular
alternative method for setting FOH grahics.
Monitor graphics are often best set
up using the ringing out
method − Ed.]
- It is unusual for controls to need to be at their minimum
or maximum settings (with a few obvious exceptions, such as
unused Aux Send controls and faders at minimum). Such a setting
is generally undesirable, as it gives no further room for
adjustment and implies that an 'ideal' setting
cannot be reached. If you find
that it is necessary to set a control this way without an
obvious explanation for the need, then it may be an indication
of an underlying problem that would be better corrected
in another way.
- Treat any comments from the audience judiciously. Enquire at
what time(s) during the event the comments relate to, and where
abouts in the venue the person was located. Show interest, be
courteous, and remember that
tastes differ from person to person.
- Get to know your mixer well − e.g. which Aux or
Effect sends are pre-fade and which are post-fade,
and whether they are pre-EQ or post-EQ.
- Activate the channel Low Cut
switches on all channels with no wanted deep
bass content − especially
on microphone channels used for vocals, strings, drum
overheads, etc.. This reduces pick-up of unwanted
etc. on those channels. [However, check that these
switches are not activated on channels with wanted bass
content, such as kick drum,
bass, etc. − Ed.]
- Keep alert, even when things seem to be going smoothly.
The unexpected can and does happen, and a rapid response
is sometimes required.
- If you are using a channel input for the return from an
effects unit, be very careful not to turn up the relevant
effect send control on that channel. If you do, the resultant
electrical feedback could seriously damage your speakers.
Preferably, mark the control in some way, as a reminder.
- Once a satisfactory mix has been established, and changing
circumstances then require further adjustments to be made,
take care to make only small adjustments (in the first
All the hard work done during sound-checks and
rehearsals can be rapidly undone by a few large changes
here and there.
- Remember that ambient noise
sources (such as HVAC, or sounds
from outside the
auditorium) may have
a significant impact on the overall
ratio perceived by the audience − especially in
low-level applications such as speech amplification.
When the PA system signal-to-noise ratio is satisfactory
but the perceived signal-to-noise ratio is poor, and a
further increase in amplified sound level is not possible
(e.g. because of feedback), steps may have to be
taken to reduce ambient noise levels.
- When using a monitor
mixer, with mixes created using the
This enables the channel faders
to be used as overall level controls for the individual
sources, allowing convenient and rapid adjustment of a
source in all the mixes simultaneously when required
(e.g. due to feedback or a sudden change in source
- When using a monitor mixer, patch
into the inserts of the
mixer outputs (usually the auxiliary
sends) rather than
the outputs via the graphic equalisers. This allows
the effect of the appropriate graphic equaliser to be
taken into account when monitoring a particular output
using its AFL (but check that
the AFL monitors the signal post-insert!).
- When using a monitor mixer, if at all possible use a
listen wedge that
is identical to the monitors being used by the
performers, so that you get the best possible match to
the sound that they hear from their monitors.
- When playing pre-recorded material that is routed
auxes (e.g. to stage monitors) as well as
via the channel fader, remember that if the
track needs to be manually faded out then you must
fade down the relevant aux
send(s) as well as the
fader − otherwise even with the fader fully
down the audience will probably still hear the material
via the monitors. (In such cases, consider
having the relevant aux send on that channel switched
to post-fade, if your
desk has that facility.) Obviously the same applies
to manual fade-ins.
Back to top.
(Also see the
Amps & Speakers page.)
- Be sure that amplifiers have an adequate output power rating
at least 30% above the power input that the speakers require
in order to achieve the desired sound level − to maintain
headroom on signal peaks.
But don't misuse the spare power by over-driving the
- Remember that the maximum output power that can be obtained
from a particular channel of an amplifier is not a fixed value
− it depends on the overall
impedance of the
speakers that are connected to that channel.
- Before switching on the amplifiers, switch on mixers,
graphics, etc., and check that the amplifier level
controls are set at minimum. Likewise, before switching
off any other equipment set the amplifier level
controls to minimum and switch off the amplifiers.
[For more detailed information on this, see
on/off procedure − Ed.]
- When using a multi-amped system
(i.e. separate amplifiers for each frequency range,
e.g. bass, mid, high), be sure that the
main graphic equaliser
is flat before starting to
balance the amplifier levels for each range. The only
proper way to balance the amp levels is to use an
analysis system or to use an audio
test CD having test tracks for each frequency range,
and check the sound levels at several places in the
venue using a good quality sound level meter. (First be
sure that the EQ is flat on the channel used for the
audio test CD!)
- Never connect a speaker output of an amplifier to anything
other than a speaker. Doing so can cause all kinds of
- Don't allow PAT testers to
stick their labels over the vent apertures of amplifiers
(or other equipment). They should know not to do this,
but it still happens!
Back to top.
(Also see the
Amps & Speakers page.)
- In terms of sound quality, this is the part of the system
that will make the most difference (closely followed by
microphones), so don't compromise on choice. It isn't
possible to properly compensate for poor quality speakers
- When choosing speakers, compare the
This is a guide to how much
you will get from
the speaker for each watt
of power input from the amplifier,
and can vary hugely between different types of speaker.
Remember, however, that the easiest way for the speaker
manufacturer to achieve an impressive sensitivity figure
is to compromise on sound quality, so be sure to check
- To get the best out of your speakers, be sure that they are
at the correct height for the situation are that they are
positioned and angled correctly. This can make a very
significant difference to the quality of the sound
perceived by the audience! For example, locating speakers
inward from the side walls, and/or angling them
slightly inwards towards the centre of the room, can help
to reduce troublesome reflections from the side walls
(especially in long, narrow rooms). And raising the height
of the speakers and angling them slightly downwards can
help to reduce the difference in sound level between the
front and back of the room. (See also the next tip.)
- When setting the position and angle of
use the 'line of sight' method to help with the alignment
of the high-mid
cabs and HF horns.
This is especially helpful to get an initial position,
before the system is ready to be switched on and
listening tests done.
First stand behind (or under) the speaker to judge what
area it is covering, and make adjustments to its
position and angle as necessary.
Then walk around the listening area, looking at the relevant
speakers − you should be able to see into the speaker horns.
(Remember to take into account any obstacles that might
not yet be in place, such as a standing or dancing audience.)
These methods work because it is the high audio frequencies
that carry the intelligibility and clarity of the sound,
and these travel in substantially straight lines, just
- If you are connecting speakers of different impedance
to the same amplifer, the speakers having the highest
impedance will take the smallest amount of power from
the amplifier (and will therefore probably produce the
- Configure the speaker system according to the
material. Powerful bass bins are not required for
reproduction of speech, or of music with minimal bass
- When positioning monitor speakers close to microphones,
take account of the
of the microphone in order to ensure minimum pick-up
of the monitor sound by the microphone, and so reduce
the monitor should be on the rear axis
of the mic, i.e. directly behind it.
use two monitors, each at
an angle of 55 degrees from the rear axis.
the two monitors should each be at
an angle of 70 degrees from the rear axis.
Back to top.
- For ease of recognition, put similar markings on
cables of the same type
(mic cables, speaker cables, instrument cables, etc.),
and store similar types together. They can be marked at the
ends with coloured tape, with clip-on identification rings,
or the cables themselves could be of a different colour.
- Don't coil cables by wrapping them around your arm − this
stresses the cable and puts a twist in it at each
turn of the coil. Instead use a good cable coiling technique, such
as the 'over-under method'.
- Releaseable cable ties and
ties are a real boon. Use them around
cables in storage or transit to prevent them becoming
tangled with each other; use them on-stage to keep coiled
excess cable lengths neat and tidy. 200 mm is a good length
to use for most cables. For bulkier coils (such as speaker
cables), two of these ties can simply be linked together
to make one (nearly) twice as long.
- If you plug together the two ends of XLR-XLR cables
as soon as you have coiled it for storage or transit,
the ends can't fall between the turns of the coil and
- If a cable is suspected of being faulty, don't put it back
in the box with the others, to be taken out again and be
used another time. Put it separately (preferably marked in
some obvious way) until it has been checked and repaired.
- Cable faults are often intermittent, so if a cable seems to
be faulty and then seems OK again, mark it as suspect and
don't use it until it has been fully checked out −
otherwise it may unexpectedly fail again during use.
- Always use proper speaker cables that are adequately
rated for each partcular job.
Don't use instrument jack-to-jack cables or microphone
XLR-to-XLR cables for the interconnections between
and speakers, or between backline
heads and their speaker
Inappropriate cables can be damaged by the high current
and voltage of speaker signals (which may in turn cause
- It's worth investing in good quality cables − but
the hyper-expensive types (such as are sometimes advocated
by audiophiles and audiophile
equipment suppliers) rarely give much added benefit in
the context of PA systems.
Manufacturers well-known for the high quality of their cables
Van Damme (the links
are to their websites, and open in a new window).
- Check mains cables frequently for signs of damage, and get
them promptly and properly repaired or replaced.
[See PAT − Ed.]
- When removing cables that have been
gaffer-taped to the
floor, don't pull up the cable from the floor with the tape
still attached to the cable. Rather, while pulling the tape
from the cable with one hand, hold the adjacent loose part of
the cable down on the floor with the other hand.
This will prevent the edges of the tape
curling around the underside of the cable − if the sticky
sides touch they are almost impossible to get apart again
and the tape will require time-consuming removal from the
cable afterwards by tearing or cutting, with a risk of
damage to the cable.
- In large systems, it can be helpful in tracing cables
(when you need to fix a problem or to make changes)
if all cables
have a unique reference number at both ends. Clip-on
numbered plastic rings are available for this purpose.
- Don't use XLR cables that have the shell of the connectors
connected to the cable screen (pin 1). This avoids the
being caused by the
connectors at cable joints coming into contact with
each other, or with adjacent metalwork.
- When wiring XLR connectors to make balanced cables, the
name 'XLR' can be used as a mnemonic for which pin is
which: pin 1 = X = Earth,
pin 2 = L = Live (hot),
pin 3 = R = Return (cold).
- The mnemonic 'Tip-To, Ring-Return' can be used to help
remember the (most common) wiring of mixer
insert jacks. So, the signal
is fed To the effect unit via the Tip connection, and it
Returns to the mixer via the Ring connection.
- When making cables to connect from a
3-pole (stereo) mini-jack
headphone output of a laptop, MP3 player, etc. to a
Line input (e.g.
of a mixer), it can be
useful to wire a pair of resistors into the
at the other (i.e. destination) end of the cable.
This avoids the possibility of damage to the laptop
or player if the hot pole of the destination end
connectors make accidental contact with something
earthed while the mini-jack is still plugged into
a headphone output. (Such an accidential
only easily occur if the destination end is a jack or
phono connector −
e.g. if jack connector tips make brief
contact with signal
earth as they are plugged in to a jack socket.)
Wire a 1 kilohm
series at the Left hot
connection, and another in series at
the Right hot conductor's connection.
This also provides
protection against damage, or current-overload
distortion, due to the Left and Right headphone outputs
being connected directly together. This might be a
permanent connection, as in the case when the
stereo output cable is wired into a single mono connector
at its destination end. Or it could occur if the two
separate Left and Right connectors at the
destination end get plugged
into linked input sockets (such as a pair of
linked input sockets on a single channel of a DI box),
in order to create a mono signal.
- When doing special things inside connectors, as
suggested in the previous entry, it's wise to label
the cable accordingly, to avoid confusion later.
(Also because such cables may be indicated as faulty
by a cable tester, even though they're wired as
- Keep all cabling well clear of transformer power
supply units (whether of the plug-in or in-line types),
as the stray magnetic field from the transformer can
into the cable conductors.
Even mains power cables should
not be located close to such power units (including
any excess length of their own supply cables), as a hum
current can be induced into the earth conductor
of the power cables − this is more likely to
cause a problem if you have any
signal interconnections. Preferably, route all
mains cables directly away from power supply units.
- When packing away bodypack
units, don't wrap the mic/earphone cable around the
bodypack. These thin cables are very easily damaged,
and repeated bending of the same points along the cable
around the corners of the bodypack can cause problems
to occur at those points.
- In an installed system, if you need to trace the route of
a cable that has been run out of sight within a wall, floor
or ceiling, then this can be done by passing a suitable
current through the cable and using a pick-up coil to
detect the resulting magnetic field produced by the cable.
If the current passed through the cable is at an audio
frequency then the signal from the pick-up coil can,
after amplification, be fed to headphones or earphones.
It can be convenient to use a frequency of the order
of 400 Hz and to use an
pick-up tester to detect the field. The test signal
can be obtained from any suitable source and amplified
using an PA amplifier to provide a suitable current
level, in which case a series resistor of suitable
value and power
rating will be needed,
to limit the current level. Alternatively, an
induction-loop driver can be used as the amplifier,
in which case no series resistor is needed.
The current can be passed down one conductor of the
cable and returned to the amplifier through another
− be certain, however, that the selected
conductors are not connected to any other equipment,
or to earth.
The amount of current required through the cable
is dependent upon a number of factors, including the
sensitivity of the pick-up equipment and the distance
between the accessible surface(s) and the cable. Care must
be taken, however, not to cause damage to the cable
by passing so much current that its conductors overheat
− extra care must be taken with
such as those within a
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This page last updated 22-Jun-2018.