What is the significance of the amount of voltage a head unit's preamp out's have?
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Anonymous
ANSWERS: 2
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The basic principle is that the higher the output voltage of the preamp output, the less susceptible it is to picking up stray noise during signal transfer to amplifier. This was seldom a concern in the past and preamp outputs were standardized to be about 1 volt maximum. However, as the power and complexity of car audio systems has increased, the chance of noise radiating into the preamp signal has grown. Let's assume that a car audio system is subject to a 100 millivolt induced noise. In the older 1 volt max system, that noise would be 10% of the signal and would probably be quite noticeable. In the new 4 volt max system, the noise is 2.5% of the signal and is more likely to be inaudible.
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4v preouts offer greater volume, allowing the input gains on the amp to be kept low, meaning everything runs more easily & is further from their peak limits, which means cleaner audio. Matching the inputs to the output levels on the ehad unit is the best way to avoid noise (assuming grounds are short & power is clean)
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