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Old 08-13-2006, 01:34 AM   #10
Audio Guy
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Re: start of newbie info thread

Another installment

Installing a Head Unit:

Power - there are 3 wires that must be connected

1) Constant power - connect to a power source that has 12 volts on it even when the car is off, this is the connection that keeps your memory settings. It is usually yellow.

2) Switched power - connect to a power source that has 12 volts ONLY when the car is turned on, this wire is usually red. You can connect this wire to constant 12 volts as well but you must make sure you turn the headunit off when you leave the car.

3) Ground - do NOT connect this to a black wire in a harness somewhere. It is black and comes with a spade connector crimped on to it, connect this to a bolt or screw behind the radio opening that screws into a solid piece of metal.


Lighting - connects to a source that has 12 volts when the lights are on, it dims the lighting on headunit a good bit when the lights are on. It is typically orange and not all headunits have this.

Power Antenna - raises the antenna when the radio is turned on, do NOT use this to your amp on because the amp will turn off when you try and play a CD. Usually blue or blue with a white stripe

auto turn on - supplies 12 volts when the headnit is turned on to switch on your other stereo components (amps, eq's, crossovers, etc ..), it's usually blue or blue with a white stripe.

Antenna - the antenna wire from the car will plug in here, atfermarket headunits typically have a 4-5" wire that the antenna wire connects into.


Speaker outputs - refer to your owners manual for color codes

RCA outputs - these are what are used to connect to external amps, eq's, etc .. Most head units have 2 or 3 sets of these, the ones with 2 sets are labeled F(ront) and R(ear). Ones with 3 sets also have a subwoofer output as well. Some headunits with 3 sets of outputs also have a builtin crossover and can be configured so that the front output is for tweeters, rear output is for mids and subs are for the subwoofer amp. You would need to consult the owners manual to see if you're headunit is capable of this and how you
would do it.

Installing an EQ:


1) Constant power

2) Ground

3) auto turn on - this comes from the headunit as described above


The RCA signal outputs from the headunit will go into the EQ signal inputs

The EQ signal outputs go into either the crossover or amp signal inputs

Installing an amp:

Power: the power and ground wire will typically be large wires

1) Constant - run a large guage cable (see owners manual for their recommendation) directly from the battery to the amp. Remember to fuse this cable in the engine compartment as close to the battery as is feasible. If you compete, it must be 18" or less from the battery (Some SPL orgs have different rules, consult them for details BEFORE you start building.

2) Ground - Typically use same size wire as constant power wire. Make this run as SHORT as possible, typically less than a foot. Find a spot on the frame and drill a small hole, sand the area until it's just bare metal about the size of a quarter or so, attach a ring terminal to the ground wire and screw it down tightly. You may also want to use a star washer to get a good connection. Alternatively, you can find a bolt, remove it, sand down the paint underneath and attach the ring terminal to that. These two
connections are CRITICAL to getting the most out of your amp.

3) auto turn on - turns the amplifier on from the headunit


There will be an RCA jack for each of the channels, make sure you put the right rca cable into the correct jack.


The outputs connect directly to the speakers. Be careful not to load the amp down too low. Low impedances cause the amp to work harder, it will try to put out more power if it can ... or die trying. Don't skimp on speaker wire size, try and match the wire size to the amps power output.
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