View Full Version : what do preamps do

10-27-2005, 07:39 PM
What do preamps do in a headunit?

If a HU only has 2 preamps outputs for the front and rear, can i still add a sub?

so if i have a HU that has 3 preamp outputs, does that mean the HU will power the front,rear,and sub. Meaning i wont have to buy an amp for the sub?

10-27-2005, 07:41 PM
Preamp sends the signal...Im not a technical person. Frost will answer this. :)

You will need an amp for your sub. You can use a LOC if you only have front and rear preamps.....

10-27-2005, 07:42 PM
Provides the signal needed to drive external amplifiers.

Some decks (like my Alpine 7894) combined the rear and sub pre-outs.

The pre-outs themselves can't power speakers; they simply provide a signal for the external amps that actually drive the speakers.

10-27-2005, 07:44 PM
they are rca outputs on the deck. they send music signals to the amps. the decks with 3 rca's, have a dedicated sub output that lets you specificly adjust the sub. you can run a sub on front and rear outputs, you just don't have a sub control on your deck and if you hook your subs to say the rear, when you fade to the rear you fade to the subs and vice versa.

10-29-2005, 07:26 PM
i have one question abt preamps voltage my p8mp has 6.5 volts preouts and 770 has 4.0 volts preout

whats the difference i know the higer the volt the better but can someone explain it to me how that works...