Does Preamp Head Unit Voltage Matter For Car Audio Amplifiers?

First of all, pre amp voltage is the level of volts provided by the RCA preout signal from the head unit, that is fed into the car amplifier. This is by connecting the RCA plugs, found on the cable into the RCA outputs connectors on the back of the stereo, near the wiring harness and connecting the other end of the plugs into the car amp's input connectors, creating an connection. This allows the car amplifier to receive a sound signal from the deck and it amplifies it into an powerful output to drive your speakers or subwoofers.

There are many head units that have different preamp voltages, low end ones, that are cheaply made, from manufactures like Ripspeed, JVC and Panasonic tend to have 1.8 or 2 volts preouts and high quality aftermarket decks from Alpine, Kenwood, Pioneer, Clarion and Eclipse have 4, 5 or 8 volts, suitable for most high end car audio purposes, for the best sound quality and noise reduction. In general, the higher the RCA volts is, it will send an better, cleaner, sounding input signal into the amp. Which will prevent hissing background noises and any other interference noises, caused by electrical interference, when you listen to your stereo because the gain setting doesn't have to be turned all the way up, reducing the noise created by the amp and signal leads. But if you have a good grounding, good high quality speaker wire and RCA leads, with proper shielding, to block out interference and static noise, then you won't hear hissing, even if you are using a 2 volts preamp output, so it is not a big issue if the wiring is good in the first place.

Also a high voltage preamp output, with decent impedance output means that the car amplifier doesn't have to work as hard, as the higher the voltage is, the more lower the gain control has to be set, as it can be matched, with the radio on a lower setting. This makes the amp run more cooler, preventing it to overheat, increasing its lifespan because the output circuitry inside it doesn't have to work as hard to create audio output for the driver, as the input signal is already strong. One thing you must understand that is a stereo with a high preamp voltage output, will not make your car sound system sound more louder, or provide more power, or reduce clipping or distortion than a stereo that has a preamp voltage of 2 volts.