Now that we have our power connections complete.

Let's move on to “audio input”.

Audio input is the sound that you would like to amplify.

In this case, it is your radio.

There are two types of audio outputs available on car stereos:

1. Amplified out or "high level out".

2. Pre amp out or "low level out".

What is the difference?

Pre amp out or - Low level out

Simply indicates that there are no amplifiers connected to the output wire of this connection. The audio signal coming out of this connection (from the radio) is just enough power to supply an audio amplifier for amplification.

What type of output signal should I use?

Well, that depends on your radio capabilities!

pre-amp level

The most desirable type of output is, pre-amp level.

This is because, when an amplifier in the radio amplifies audio, it will create a specific amount of distortion.

Distortion is measured by:

• T.H.D.- Total Harmonic Distortion

When you add a larger amplifier, you are basically taking the distortion from the radio amplifier and amplifying the distortion.

So, lets assume your radio is generating a rate of 1% t.h.d. and the larger amplifier (the one you are adding). Has 2% t.h.d.

More about output signals

With low level out, you have minimal distortion, as there is very little amplification.

You can however, purchase what is called a "High to low level adapter".

This device will bring the high level down to a low level.

This will help with distortion rate, however, it will still be there, as the high to low level adapter will try to remove as much distortion as possible.

For the lowest distortion rate possible, you should choose the higher quality high to low level adapter, for better audio reproduction.

A High to low level adapter can be purchased at most audio retail or online stores.

Note:

Many amplifiers now come with built in high to low level adapters.

You should refer to your owner's manual or it should indicate on the amplifier "high level in", or may indicate "speaker in".