When it comes to sound systems, all of the sources for sound fall
into one of two main categories: a) Electrical sound sources and
b) Acoustic sound sources.
Electrical sound sources are those where the sound originates as
an electrical wave generated by some piece of electrical
equipment. Examples of Electrical sound sources include: recorded
sound (CD, record, or cassette tape player) and electronic
instruments (keyboard, electric guitar, electric drums, etc.).
Many Electronic sound sources cannot be heard at all without the
aid of a sound system.
Acoustic sound sources are those which naturally make sound that
can be heard (at least to some degree) without a sound system.
Examples of Acoustic sound sources include: voices (talking or
singing) and acoustic instruments (acoustic guitar, horns, drums,
Below, we will discuss the various ways to connect Electronic and
Acoustic and sound sources to a sound system:
Connecting Electronic Sound Sources
In order to connect an Electronic sound source to a sound system,
you usually just "plug it in". That is, an Electronic sound source
usually outputs an electronic signal suitable for direct
connection to a sound system (the mixer).
CD, Record, and Cassette Tape Players
CD, record, and cassette tape players all have "RCA jacks"
on them which can be used to connect them to the sound system.
Some mixers also have RCA jacks for input, but many only have XLR
and 1/4" jacks. In this case, an RCA to 1/4" adapter is
If you have enough channels on the mixer, you may connect the
left and right signals from the CD, record, or cassette to two
mixer channels. However, if channels are scarce or if the system
is being run mono (rather than stereo), then you may use a
Y-adapter to bring both signals into the same channel.
If you are playing "Split-Track" performance tapes where the
music is on one track (i.e. the right) and a rehersal version of
the singing is on the other track (i.e. the left), then you MUST
connect to two mixer channels in order to be able play just the
music for the performance.
If you try to connect a record player to a mixer, you should
be aware that older record players put out a special signal called
"Phono" which requires special equalization to make it sound
normal. If your mixer does not have a "phono" input (and most
don't), then you may need to make drastic changes to the tone
controls (equalizer) to get the records to sound OK.
Electronic Instruments - Keyboard, Electric Guitar, Electric
"Electronic" instruments such as guitars have a built in
microphone or magnetic "Pickup". Keyboards output an electronic
signal. These signals may be connected to a guitar or keyboard
amplifier and/or the sound system mixer.
If the distance between an electronic instrument and the mixer
is much more than 25 feet, a "direct box" should be used to
convert the un-balanced high impedance signal from the instrument
into a balanced low impedance signal which can travel a longer
distance (hundreds of feet) without picking up significant noise.
The direct box has an input jack that accepts the 1/4" plug of a
guitar cord and an output jack that accepts the XLR plug of a
Usually, an electric guitar player and often a keyboard player
will want to have their own guitar / keyboard amplifier. This
serves two purposes: a) the musician can hear what they are
playing better with a dedicated amplifier than they can through
the monitor system and b) the musician may want to add special
effects that are only available on the guitar / keyboard
amplifier. If the guitar / keyboard amplifier is being used to add
effects, then it a direct box cannot be used. In order to get the
"sound" that the musician wants, you have to place a microphone in
front ot the guitar / keyboard amplifier to pick up the sound of
that instrument for the "House mix". Usually a desk mike stand
(6") with a Goose neck (12") works best in this application. If
the amplifier has treble and bass speakers, place the microphone
half way between them. If it has several full range speakers,
place the mike directly in front of one speaker.
Another way to connect electronic instruments to the sound
system is via an FM transmitter and receiver. This is most
appropriate for guitar and horn players that want freedom of
movement. The FM transmitter has a guitar cord which plugs into
the instrument and the FM receiver has another guitar cord which
plugs into the mixer.
Connecting Acoustic Sound Sources
To connect an Acoustic sound source to a sound system, you usually
need to use a microphone to convert the "acoustic" sound into an
Acoustic sound or "sound waves" are rapid minute variations in air
pressure created by a person's voice or an acoustic instrument. A
microphone is used to convert these sound waves into electrical
signals suitable for input into a sound system.
Voices - Talking or Singing
To get a person's voice into a sound system, you need a
microphone. There are many different types of microphones which
can be used depending on the particular situation.
Wired / FM Microphones:
Most microphones require a cord to carry the electrical
sound signal from the microphone to the mixer.
When the cord presents a problem such as a trip hazard or
limits the movement of the performer, then an FM microphone should
FM microphones contain a small FM transmitter which sends a
radio signal through the air to an FM radio receiver. The FM
receiver is then connected to a mixer input.
Placement of the FM radio receiver and its antenna(s) is very
important. It should be close to the microphone (20 to 100 feet)
and not near sources of electronic interference (i.e. CD player,
effects processor, keyboard, or computers).
You get what you pay for in FM microphones! The more expensive
units are called "True Diversity". That means they have two
antennas to receive the radio signal from the microphone. The
purpose of two antennas is to minimize the multi-path cancellation
effect. If one antenna is receiving the signal directly from the
microphone and also receiving a reflection of the same signal
(i.e. off a metal object), the two signals may be out of phase and
cancel each other out, causing "drop-out". However, with a second
antenna (properly located), it should not be receiving the same
reflected signal and therefore its signal will not be canceled out
(at the same time). The receiver automatically switches to
whichever antenna is receiving the strongest signal.
If several FM microphones are used at the same time, each must
operate on a different radio frequency.
The newest series of FM microphones are called UHF. This means
they operate on a very high radio frequency around 900Mhz. Usually
they will provide better performance than the VHF units.
Unidirectional / Omnidirectional Microphones:
Unidirectional (also called Directional or Cardoid)
microphones "hear" or pick up much better from the front than they
do from the sides or rear.
Unidirectional microphones are usually best for sound
reinforcement to prevent feedback (because they don't pick up much
sound from the main or monitor speakers)
Omnidirectional microphones hear or pick up sound from all
Omnidirectional microphones cause feedback easily.
Omnidirectional microphones sometimes sound more natural for
A Laveler microphone is a small microphone which usually
has a clip to attach it to the performer's clothing.
Laveler microphones provide "hands-free" operation.
FM Laveler microphones provide the greatest freedom of
Laveler microphones usually do not sound as natural as hand
held mikes and are less desirable for singing.
Depending on the clothing being worn, location of a Laveler
mike is sometimes a problem. It needs to be located as high as
possible and centered with the mike pointing straight up. The best
location is clipped on a tie, just below the knot. If the
performer is not wearing a tie or a buttoned shirt, it may be
difficult to find a place to clip the mike.
In theatrical performances, they often hide an FM Laveler mike
in the performer's hair either over one ear or above the
It looks better if you get the performer to wear the FM
transmitter in a pocket or under their clothes and route the wire
to the microphone through their clothes to minimize visibility of
Recently, Headset microphones have been gaining
popularity. Many professional performers use a Headset
A Headset microphone provides the "hands-free" operation of a
Laveler with superior sound quality for singing and better
An FM Headset microphone provides the best sound quality along
with "hands-free" operation for a singer.
When combined with an FM Instrument pickup, an FM Headset mike
gives a singer / instrument player complete freedom of
A PZM (Pressure Zone Microphones) looks like a flat metal
plate with a small raised area containing the microphone element.
It may be placed directly on a flat surface such as a floor or
table top to pick up sounds from as far as 10-12 feet away.
Sometimes, a shield is used to limit the sound pickup angle.
Tonal quality of a PZM microphone may not be as good as other
mikes, but they are useful when it is not practical to directly
mike the performer.
Acoustic Instruments - Piano, Guitar, Horn, Drum,
There are a great number of ways to mike acoustic instruments.
Experiment to find out what works for you and the
First, hope that the performer is using a guitar with a
good quality built-in Pickup. This can be directly connected to
the mixer. If the mixer is more than 25 feet away, a direct box
should be used.
If the guitar doesn't have a pickup (or has a pickup that
doesn't sound very good), use a directional microphone on a boom
mike stand. Place the mike as close to the opening in the guitar
as possible without being so close that the performer will hit the
mike when playing the guitar.
Similar to electric guitars, an accoustic guitar can be used
with an FM transmitter and receiver to connect it to the sound
system and allow the performer freedom of motion.
A good quality Laveler microphone clipped onto the bell of
the horn often works well (be careful not to scratch the metal of
the horn or you will have a very angry performer on your hands!).
An FM Laveler gives the performer freedom to move. Some Laveler
style microphones come with a special clip for horns which is
padded with felt so it doesn't scratch the horn. It also allows
the microphone to face into the bell of the horn.
A directional microphone on a straight, goose-neck, or boom
mike stand can also be used.
On a Grand Piano, the lid should be opened (probably on
the short stick). An omnidirectional microphone on a boom stand
can be positioned so that it hovers near the middle of the
strings. Tonal quality can be changed by moving the mike towards
lower or higher strings.
An alternative is to use a PZM microphone attached to the
inside of the Piano lid or possibly attached to the bottom. If you
are in a hurry, you can even place a PZM on the floor under the
Since the wood of the Piano tends to direct sound from the
speakers back to the microphone, feedback may be a problem.
An upright Piano can be miked with a PZM inside the lid or a
mike on a boom stand behind the Piano. Tonal quality varies
greatly with mike placement.
Before we complete the discussion of sound sources, there are some
related areas we should discuss:
Some microphones contain circuitry which requires power to
make the microphone operate. Condensor microphones are one
example. Some mixers provide "Phantom Power" for this purpose.
Phantom Power is usually 9 to 48 VDC.
If the mixer has Phantom Power, it usually has a switch to
turn it on or off. Sometimes there is a switch for each channel
and sometimes the switch applies Phantom Power to 4 or 8 channels
at a time. Be sure the Phantom Power switch is turned off if you
are not using microphones that need it. Try not to leave Phantom
Power turned on to a mixer channel connected to a Dircet Box or to
a microphone that has an On/Off switch - it may cause
Microphone Proximity Effect:
Directional mikes always have a "proximity effect". When a
person is in close proximity to the microphone (2" or less), there
is a dramatic increase in the low frequency (bass) response.
The proximity effect can be used to advantage by constantly
staying close to the mike (less than 2") for a more POWERFUL
Occasionally getting close for effect adds variety.
When a large number of microphones are used for a singing
group, the proximity effect is usually a disadvantage: Most of the
time, singers are to far away from the mike (8" to 18") for the
proximity effect, so the sound system is set up to sound best
without the proximity effect. On solos, singers get in close (2"
to 4") and the proximity effect makes them have too much
When the system is set up primarily for people using mikes at
8", then individuals should not get closer than 3" to
prevent excessive bass.
As mentioned above, the distance the sound source is from
the microphone is very important. For singing and speaking, 2" to
4" is the optimum distance.
Equally important to distance is the angle of the microphone.
When using a hand held microphone, it should be positioned just
below the mouth, even with the chin. The microphone should be held
almost vertical with only a slight tilt toward the mouth. You
should speak or sing across the top of the microphone. If you
speak directly into the top of the microphone it will cause
excessive breath noises and "P-popping".
When a hand held mike or a laveler is not appropriate, then a mike
stand is probably the best solution. Again, the proper choice of
mike stands can make a big difference:
Straight stand - usually suitable for a speaker or singer
or a group of people.
Boom stand - helps get the mike closer to a person playing a
piano, keyboard, guitar or other instrument.
Goose-neck stand - often useful to get a mike close to an
Hanging mikes - sometimes the best way to mike a choir is to
hang microphones above and in front of them.
Podium - often a lecturn or podium has a goose neck microphone
It is important to understand the different types of cords that
are used to make the connections between the various parts of a
sound system. All cords used to connect inputs to a sound system
or to connect the various parts of the sound system together MUST
be shielded cable in order to prevent the system from picking up
hum and noise. The only exception to this is the connection
between the amplifier and the speakers which does NOT need to be
The cords used to connect sound sources to a mixer fall into one
of two categories:
The term "unbalanced" refers to a two conductor cord where
one conductor is a grounded shield and the other conductor caries
the sound signal. However, the sound signal must also return via
the shield. The connection is referred to as "unbalanced" because
one conductor is grounded and the other is not.
Unbalanced cords may use RCA jacks, or 1/4" plugs.
Unbalanced connections generally should not be used for
distances much greater than about 25'. At greater distances, an
unbalanced cord picks up too much electronic "hum" and noise.
Although the shield protects the inner conductor from picking up
hum and noise, since the sound signal must return via the shield,
it is affected by the hum and noise picked up by the shield.
The term "Balanced" refers to a three conductor cord where
the outer conductor is a grounded shield and two inner conductors
carry the sound signal. The connection is referred to as
"balanced" because the two inner conductors that carry the sound
signal are "balanced" at the same voltage level.
Balanced cords can carry sound signals much further than
unbalanced cords, typically several hundred feet. Balanced cords
are not nearly as susceptable to picking up hum or noise because
the sound signal only goes through the inner two conductors and
never uses the shield. Therefore hum and noise picked up by the
shield is simply grounded.