2volt / 4volts

[Bluliner]

The goal of a high voltage pre-out is much the same as twisted pair RCA's and keeping your signal wire away from power wire.

Ever wonder why you don't need a lot of shielding for speaker leads yet you do for signal leads? It's all do to voltage. There's always going to be a few electrons here & there that get, shall we say, confused and just kinda hang out where they are. In a low voltage signal lead, that can be a problem as there isn't a lot of electrons being passed through (compared to speaker leads). Hence, you get into the mathematics of the signal to noise ratio. Boost the signal with the noise being the same and you never notice as the ratio is much more favorable.

The fact that you can keep the gains down on your amp is a nice unintended consequence. The higher voltage signal going into the amp means you're not amplifying much, if any, noise that's picked up through the RCA run AND the noise floor of the amp stays low. WIN-WIN

That's the good news...here's the bad news.

Do you really think every head unit that's rated @ whatever voltage really does that? Unfortunately, they do not. Furthermore, the resistance of the RCAs will lower the voltage that amp sees @ it's input anyway. I've seen nice Alpine HU's meter out below 2v at the end of a nice set of RCAs.

So how do you get around that? 2-ways:

1. Use home audio RCA's - they're thicker, have less resistance, but forgo twisting in favor of shielding.

2. Line drivers

I swear by line drivers, however they can cause more problems than they solve. For instance, you can run into ground loops & other noise related issues if you have a bad install or bad unit. The better ones are not exactly cheap and some can take up as much room as an amp; so there's a give & take with them. But if you're not a hack installer and don't mind having a processor that's not in the dashboard, line drivers are great as most processors will do a better job than what comes in a HU and boost the RCA voltage. The ones I've always used have been Audio Control pieces as every processor they make is also a line driver. I also know some people with car PC's who have used Audio Control line drivers with great success.

So a quick wrap up:

High voltages going through the RCA's is good, some manufacturers lie about their specs, and line drivers (or processors that do the same thing) are usually money well spent.

[Quiet]

This thread won't die.

Generally speaking:

Higher voltage out, lower noise floor = better signal quality to your amp

No loss in volume if you adjust your amp gains properly

You are better off not running a line driver if your intention is only to overcome noise. Too much chance to encounter ground loop or does nothing for you by amplifying the existing noise already in signal. Use a line driver for splitting signal among multiple amplifiers.

/thread again.