right way to wire up a line driver

Hi and welcome.  Sure, you can generally tap the power/ground/remote at the HU for something like a line driver since the current pull is relatively small.  It doesn't matter how you do ot, but I suggest you disconnect the HU and solder the wires together.  Disconnect your battery before you begin. 

I assume this means you are not using the amps built into the HU to drive your speakers, so its current draw should also be small.  The only danger of tapping more than one device off the factory radio power is it is generally a 10 or 15 amp fuse and you might blow it.

Now on to a more basic question: whay do you feel you need a line driver?

Thanks alot Dyohn...so either way is right but the solder wire is probably a better way so thats what I`ll do.

I have an Alpine 9813 w/ the internal amp off....

The reason why I think i need one...well I have the 9813 running to a dqx then to the sub and component amp. I measured the output of the 9813 and while its rated @ 4 volts I found that its only putting out .5!...I wasnt able to level match the dqx b/c I dont have enough signal from the HU going into the dqx. I found I had to bump up the gains of both amps to get adequate volume but found after I did this that my noise floor was really noticeable. I bought An Audio Control Overdrive to send 7.5 volts to input gains of the dqx so I should be able to send enough voltage to the inputs of the amps thats I dont have to touch my gains and leave them @ minimum....which brings up another question I hope you dont mind anwering for me:

.My amps are rated to handle 4 volts and 2 volts min input sensitivity. My DQX lets me know how much voltage is being sent to each amp up to 5 volts.  If I try to use 3:1 overlap to set the gains    does this mean I need to bump up the gains on the amps any way?...For example if the dqx isending 5 volts to the sub amp that has 2 volts min input sensitivity do I still need to turn up the gains a hair on the amp?...Hope that made sense!!!!! Thanks again 

OK, a couple of things.  First, any device, whether its the head unit or your line driver or the DQX only puts out the maximum rated line voltage with the volume all the way up and usually while clipping.  Line voltage will vary from zero to max depending on the program material and the volume control setting.  You should have no problems level matching the Alpine output to the DQX input.  Second, if your amps can only handle a 4 volt input and the line driver is sending them up to 7.5, then perhaps the "noise floor" you are hearing is being caused by too hot an input to the amp and no matter what setting you use for the input gain it will be present.  The DQX has adjustable output levels and for your amps will probably need to be set to 2 volts.  Follow the steps on page 11 of your DQX owners manual and see if it works for you.

In general, you should set your input sensitivities (gains) so that all your maximums before clipping match, then back them of from there if necessary.  Leaving the input on your amps set to minimum and then boosting the pre-amp inputs to achieve acceptable volume is just as bad as boosting amplifier gain to force higher outputs.  Whether it's introduced in the HU, the amp or somewhere in between, noise and dostortion is still noise and distortion.  :)

Let me tell you what I did . I figured out where my HU clips using a 1k  0db test tone 24 on the alpines volume knob so 23 is the highest setting w/o clipping. Heres where my problem is, the DQX has an input maximized led that should start to flicker once the DQX`s input gain is matched to the HU....I turned the input level knob all the clockwise but that led never starts flickering for me...I used test tones and music nothing the only way it starts flickering is when I turn up the volume on the HU therefor clipping the signal. The maximum input level on the DQX is 7.5v I dont know what the minimun is but I know thats its more .5 volts because thats the highest measurment I got @ the output of my HU with the volume @ 23. So since the input led never flickers my output leds barely come on. I should tell you that the DQX also has output voltage indicators that let you know how much voltage its sending the amps. The most I`m sending the amps is 1 volt b/c theres a weak signal to begin with from the HU. So with the volt going into the amps and both their gains turned all the way down it sounds real clear but the volume is considerably low, not that I like my music super loud or anything but this is barely louder than road noise. So now I have an amp that can take 4 volts min and its only getting 1 volt and I have another that can take 2 volts min and its getting 1 volt if I use 3:1 gain overlap that would mean the amp needs to be getting 3 times the voltage it can handle right so I should set the gains on both amps to read 0.33. Am I right in thinking this?

On my comp amp its easy to know when the gain is set to 0.33 b/c it has the voltage written by the gain knob but when I set it to .033 I get the hiss actually even when I lowered the gain the hiss is still there the only time its not is when the gain is all the way down.

So I figured the Overdrive would be able to maximize the input level on the DQX ...even if the Overdrive doesnt put out the full 7.5v it should be more than what the HU is putting out So I should be able to get the Input led to flicker w/o having to turn my hu vol knob into clipping. So once i get the input on the DQX maximized I should be able to get more voltage out to the amps ...unclipped b/c the vol knob on the Alpine would still be @ 23. Am I going about this the right way? 

Sorry theres alot there to read !!!! But I`ve been playing around with this for a week...and I`m a little obsessed!!! lol 

i am not entirely familiar w/ the dqx, but when remember that when you adjust your input signal from the deck and set it, that the output is idependent, so don't try and adjust the input if your output makes the light flicker, I was doing that and eventually realized not to. Are you all your bands set to flat, that will make a difference as well. 

Hahaha I have done that before !!!! But this time I`m positive that its on AC (you planted the seed of doubt in my mind so I tested again...lol)...I managed to get .8 mv with the volume set @ 31 (clipped signal)..and .1mv with the volume on the hu @ 23 (right before clipping)

Dyohn ....are there any tests I can run to see if the h/u is defective?...I was planning on measuring the output of the rear channel. But other than that can you reccomend anything else? I take it you dont think I need the line driver and I felt the same way but the more I try to figure out the problem the more I keep coming up with a line driver being the solution!...Thanks again guys for responding.