High Level Inputs

The Lowdown on High Level Inputs

So you just purchased an amplifier for your vehicle's sound system.  Did you get a wiring kit to go along with it?  Hopefully you did because it means you can get to installation the amplifier sooner rather than later.  Most amplifier installation kits include 1 set of RCA cables

that send the signal from your radio via a pre-amp output to the input side of your amplifier.  This is how the amp "knows", if you will, the music that is playing on the radio.  RCA cables and pre-amp outputs have been used to do this in vehicles for over 30 years.  However, now many amplifiers

will accpet high level, or speaker line inputs.  This is to explain the difference and give you some more insight as to which ones you should use.

Traditional RCA Cables.

Most radio or head units come with at least 2 channel RCA pre-outs.  What this means is that the radio is sending the signal to these output connections before sending that signal to the internal amplifier that is built into the radio.  This is usually done at somewhere between 2-5 volts.  Traditionally, amplifiers could not handle

the amplified, higher voltage signal that is coming from the speaker wires.  The signal was passed via RCA connections which had a center conductor which is the positive and an outer shield which is the negative.  Usually the RCA cables are twisted internally inside the insulattion to try to prevent noise.  The ground or negative side is grounded

to the actual radio chassis whcih is in turn, grounded to the chassis of the vehicle via the ground wire at the power connection.

High Level or Speaker Level Inputs

Nowadays, most amplifiers accpet high level inputs up to 10 volts.  This means that you can actually connect speaker wire, via the radios speaker wire connections and run speaker wires to the amplifier.  Sometimes you made need some speaker wire to RCA converter cables depending on the amplifier, but the signal coming form the radiois being sent to the external amplifier, AFTER it has already

been amplified with the radio's internal amplifier.  With this, the positive signal is sent via the (+) wire and the (-) is sent via the negative wire.  The signal ground is coming from the internal electronics of the radio rather than the chassis of the car, just how your speakers work.  Most of the time, the signal coming from most radios is about 10 volts.  This meansthat the signal that is actually

coming into the amplifier is at a higher voltage which means less noise, and generally better sound quality.  Also, every other electrical item in the car is grounded to the chassis which allows for a good amount of noise to enter the system.  With high level inputs, instead of the ground for that signal coming from the chassis, it comes from the internal electronics of the radio as we stated above.  Another advantage

of high level inputs is that the cost is usually much cheaper.  RCA cables can be expensive, especially if you need to make long runs.  Speaker wire is relatively cheap.  Depending on the amplifier, you may need adapters as we stated above, but running the speaker wire is also much easier and less bulky than RCA cables.

If your amplifier will accept high level inputs, use them!  If you are old school and you just want to run RCA's becasue that is the way you have always done it, that is fine too.  But, when you run RCA inputs you get the following:

You will usually have to select a switch or tell the amplifier what the input voltage is, but when in doubt, high level out!