Yes, they do make a difference when placed iimmediately after the source unit. Many people place them near the amps in their trunk, which in my opinion, defeats the whole purpose. Doing it that way is basically sending a low voltage signal all the way into the trunk, into the line driver, which in turn boosts the low noisy signal even more and sends it to the amps/processors.

Which would you rather have: a low <1V signal coming from your head unit and going into your amps/processors in the trunk -or- would you rather have a nice high voltage signal coming from a line driver located near the head unit going to your amps/processors in the trunk? I'd take the latter any day.

I am one of those people that believes turning the gains up on an amplifier does increase noise floor. I know there are people here that will argue against this, but I will continue to stand behind my belief on that. Not everyone uses megabuck amps with ultra low noise floor.

 

I agree u want to set the gain on the amps low. IME it does make a difference, no matter how expensive the amp.

 

There are other differences between two completely different head units, than just their max output voltage.

 

I traded for a tru line8 that I haven't had a chance to install yet. I am running a p99rs and using zapco z150.4 and zx200.4 amps. What kind of difference do you think that I will see? Should I try to install it in the front of the truck or back by the amps? Is that correct that I should try to mount it up front somewhere? Will I gain much by using it? I have never used one before.

 

I traded for a tru line8 that I haven't had a chance to install yet. I am running a p99rs and using zapco z150.4 and zx200.4 amps. What kind of difference do you think that I will see? Should I try to install it in the front of the truck or back by the amps? Is that correct that I should try to mount it up front somewhere? Will I gain much by using it? I have never used one before.

 

IMO you won't see much diff at all; in fact u may get some degradation in SQ or at the very least some coloration. The P99 has really strong output voltages. KISS is usually the best way to go.

As for the comment about the fact that I compared 2 completely diff HU's, you're absolutely correct. I didn't say I was logical or smart I just said i noticed a difference; clutching at straws, I know.

 

IMO you won't see much diff at all; in fact u may get some degradation in SQ or at the very least some coloration. The P99 has really strong output voltages. KISS is usually the best way to go.

As for the comment about the fact that I compared 2 completely diff HU's, you're absolutely correct. I didn't say I was logical or smart I just said i noticed a difference; clutching at straws, I know.

Did you readjust the gains on the amps after swapping HU's?

 

If the source already has decent outputs (2V or more) then I wouldn't even bother using a line driver. Less than 1V? It might be a good idea. This comes from experience. Last summer I used a couple of miniDSPs for my install, and I was so annoyed by the maximum 0.9V they put out! It just was so weak. I was actually going to buy line drivers to use along with them, but I opted to sell the miniDSPs instead.

 

I think the OP is asking whether or not using a line driver with an already high voltage HU makes a big difference.

The only difference it will make is that the signal will obviously be stronger. It's not going to magically make things sound better. You are just adding more unnecessary devices to the signal path. Why do that?

My rule of thumb is to always choose a HU or DSP with the strongest pre-outs as you think you will ever need or want. Get it right with the HU or DSP where it matters the most and be done with it.

 

I installed a line 8is in my system as close to the amps as possible which is what tru recommended. It made a huge difference, my system sounded good before but the line driver made a big difference. Much more dynamic after the line8 install.