Amplifying your sound - Amplifiers and Mixers

In the first post of this series, we talked about health and safety. Now that we know the necessary precautions we have to take, we can talk about the main devices we are dealing with: amplifiers and mixers.

1. What is an amplifier?

Amplifiers are not unique to music. In fact, they can be found in most, if not all, electronic equipment. Their basic function is to increase the magnitude of a signal, which is itself defined as a current that varies through time. Microphones, electric instruments and digital devices feed signals to audio amplifiers and mixers, which then amplify (i.e. increase loudness)them to make them come out of speakers with the volume and characteristics that we want. 

The main difference between an amplifier and a mixer is the number of signals that each of them can handle. The amplifier is designed for only one, while the mixer can process multiple signals at the same time. Due to this, amplifiers tend to have a built-in speaker, while mixers don't.

2. Basic elements of an amplifier.

• Gain:  On amplifiers/mixers there is a dial called 'Gain'.  You will use this to increase the volume of the microphone, instrument, coming into the amplifier.  

• Volume/Fader: It allows you to control the volume of a track/instrument/microphone going out of the amplifier/mixer through, for example, speakers.

• EQ: It is the balance between the volumes of different frequency bands within an audio signal. These frequencies range from low to high.  Sometimes they are labelled as Bass, Middle, and Treble on amplifiers.

In addition, you will find in both devices a power supply, which enables it to work.  Also specific leads are used to connect instruments into the amplifier/mixer.   Mixers have LED indicators to show whether the signal strength is at a safe level (green), slightly high (amber) or high enough to potentially cause auditory damage and make a horrible sound (red).  Amplifiers may have one light which changes colour to show the signal strength. 

Amplifiers and mixers come in different colours and weights. The type and location of their sliders and knobs also varies. Amplifiers can usually be set on poles, while mixers sit on a stand or table.

3. Which one to choose?

When deciding what to get for your PA system, consider:

• The amount of signals you need to amplify. Count instruments, microphones if you sing or want to address the audience between songs, and backing tracks.
• Your type of instrument so that you purchase the correct amplifier for it. For example, a Bass amp is designed to handle lower frequencies, a keyboard  amp is designed to handle low to high frequencies.  
• Your music genre. Some of genres favour tonal coloration and distortion, while others don't.  Having an amplifier with a range of effects may be better than one that does not, unless you intend to purchase another device to handle effects, such as a guitar pedal, which is then connected into an amplifier or mixer.
• The size and acoustics of the venues you are most likely to play at.
• The means you have to transport the amplifying device, along with your instrument and other devices (microphones, speakers, etc.), to venues.

If you have doubts or questions, it is worth to check whether music stores in your area offer demos.  You can also speak to an experienced musician or sound engineer you know. 

Bear in mind that a PA system can have both mixers and amplifiers. As an example, the Millicent Stephenson Trio has the singer's microphone, the saxophone and the keyboard connected to a mixer, whilst the bass is connected to a separate amplifier. There are two reasons for having it this way. The first is that the low frequencies of the bass can overpower the mixer's system and drown other signals. The second, that amplifiers designed for electric guitars and basses don't usually seek to reproduce the signal as accurately as possible, but rather, they add tonal coloration and distortion to the sound. Due to this, and given the limitations of the context, the bass will have more character and freedom if it is not added to the mixer. 

 
We hope that this article clarified some of your doubts about amplifiers and mixers. Please, share it with anyone who could also benefit from this information.