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ByEziukwu David Ifeanyi

Direct Injection Box

DI Boxes

The DI (Direct Injection) Box is a device typically used in recording studios to connect a high-

impedance,line level, unbalanced output signal to a low-impedance microphone

level balanced input, usually via XLR connector. They provide ground-lift facilities to avoid

ground-loop hum problems caused by multiple ground paths.

ByEziukwu David Ifeanyi

Considerations in choosing an Amplifier

Considerations in choosing an amp

When choosing an amplifier for a loudspeaker system, there are a number of factors to consider.

It is important that the power rating of the amplifier not be too low; otherwise you will not be able to utilize the full SPL potential of the loudspeaker system.


A low power amplifier with inadequate power can actually damage loudspeakers by being driven into clipping. Clipping occurs when an amplifier is asked to produce output beyond its designed limits.

When an amplifier undergoes severe clippings, DC voltage is produced when a sine wave or complex wave (AC) is cut off at the electrical ceiling and floor of an amplifier. The power output is doubled.

The DC voltage will heat up the voice coil of the loudspeaker causing the glue, holding the voice coil to melt; the voice coil itself will exceed its thermal limitations and will expand. This expansion will cause it to get stuck in the voice coil gap.

Also it is important that the power rating of the amplifier not be significantly more than the loudspeaker can handle because it becomes easy to destroy the loudspeaker with excess power or with excessive excursion causing the driver to “bottom out”.

The amplifier must be able to drive the collective load of the loudspeakers if it is connected in a series or parallel or series-in-a-parallel connection. The impedance of each individual loudspeaker & the NET load impedance must be calculated.

ByEziukwu David Ifeanyi

Amplifier Power Rating

  1. Amplifier Power Rating

The power rating of an amplifier will state the power that the unit will deliver into a specified load – at a specified distortion level & over a specified frequency range.

An amplifier specification is referred to as “X watts RMS into X ohms” can also be known as continuous average power rating.

Continuous power is the ability to do work continuously as opposed to periodically i.e. programme or peak power.

Note: This is the power rating specification an engineer should consider when looking into the power rating of an amplifier.

An amplifier’s specification usually states its:

Continuous Power Rating is 100 watts into 8 ohms Programme Power is 200 watts into 8 ohms
Peak Power is 400 watts into 8 ohms

ByEziukwu David Ifeanyi

Amplifier Maintenance

  1. Amplifier Maintenance
    1. ensure make sure the fans work clean the fan filter regularly
    2. check & tighten all connections regularly
    3. change the fuses regularly
    4. always earth/ground the amplifier
    5. keep a spare amp at hand
    6. keep all audio equipment cool, clean & dry
ByEziukwu David Ifeanyi

Power Amplifiers

Professional power amplifiers work so hard, it is very important to look after them & check them regularly. An amplifier that dies can often destroy all the loudspeakers connected to it.

ByEziukwu David Ifeanyi

Power Amplifiers

Power Amplifiers

A power amplifier is a signal-processing component whose function is to increase the power of an audio signal. It will take the small signal from the mixing console & turn it into a large signal that will drive the speakers to high volume levels.

In sound systems, the power amplifier is
always the final active component in the signal chain, located just before the loudspeakers.

ByEziukwu David Ifeanyi

What is Sound?

Sound is a disturbance of the atmosphere that human beings can sense with their hearing systems. Such disturbances are produced by practically everything that moves, especially if it moves quickly or in a rapid and repetitive manner. The movement could be initiated by: Hammering (rods), plucking (string), Bowing (strings), Forced air flow (vibration of air column – Organ, voice). Vibrations from any of these sources cause a series of pressure fluctuations of the medium surrounding the object to travel outwards through the air from the source.

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