Line driver location

fordtough1 · Post by **fordtough1** » Mon Apr 14, 2008 4:17 pm

I'm sure this has been covered before, but I can't find it.

Why does it matter where the line driver is located. Everyone always says to put it as close to the headunit as possible, but I don't understand why. Is it to reduce noise in the system?

Reason I ask is because there is very little accesible space near the front of my car. Does it really make that big of a difference where you put it?

Oh, it's a TLD 66 if it matters.

Thanks guys

Post by **stipud** » Mon Apr 14, 2008 4:34 pm

The main purpose of a high voltage signal is noise rejection.

A car is an electronically noisy environment, especially considering the number of gizmos, and how your entire chassis is used as a conductor. Big fat power cables, electrical switches, motors, etc will all give off electrical interference.

Now, let's say you have a 0.2v hypothetical noise spike, being radiated into your RCAs as they run along your chassis. Assuming you have a 1 volt RCA being passed to the rear, this 0.2 volt spike would be a whopping 20% of your signal voltage, so you will hear it very clearly with your amp gains set for 1 volt. On an 8 volt signal, that same 0.2v spike is only 2.5% of the signal voltage, so it will be MUCH less audible than the noise spike at 1 volt.

Now with your line driver situated in the rear, the noise spike will occur closer to the front of the car. If this happens, the line driver will amplify the 0.2v noise to 1.6v, where it will still be 20% of the 8 volt input signal. As such, this is really no different than running the 1 volt signal. In fact, having more items in your chain will only add more noise, so any theoretical advantages might be lost.

So yeah... the main purpose of linedrivers is to boost the signal up front, so it can make the dangerous journey to the rear of the car, and be less affected by radiant noise.

fordtough1 · Post by **fordtough1** » Mon Apr 14, 2008 5:37 pm

I see, I knew there had to be a good reason to have it as close to the headunit as possible, I just never had it explained to me. That however makes perfect sense.

Thanks stipud

trckydve · Post by **trckydve** » Mon Apr 14, 2008 11:26 pm

So why do people mount them in their trunk? I had to go to considerable effort to get mine mounted up front but I see a lot of people mount them in the trunk next to the amp. Why would you do this if it more or less defeats the purpose of the line driver?

Post by **stipud** » Tue Apr 15, 2008 6:04 am

trckydve wrote:So why do people mount them in their trunk? I had to go to considerable effort to get mine mounted up front but I see a lot of people mount them in the trunk next to the amp. Why would you do this if it more or less defeats the purpose of the line driver?

Well, if you had a ZPA or something that absolutely NEEDED an 8 volt input signal, and your entire dash was filled with concrete, then I suppose it might be forgivable.

I assume most people use it to boost their input voltage, without touching their amp gains (leave them set for 1 volt or something). All of a sudden the setup is "louder" (despite that they are clipping like mad), but they feel like a champ because they got "more".

Always install your LD as close to the headunit as possible. You can usually zap strap it up to a bundle of wires (TLD66 might be a bit more challenging). If you can, pull out your glove box... I usually mount it behind them somewhere, where there us usually lots of room.

Post by **Bfowler** » Tue Apr 15, 2008 7:43 am

yes to all that tom said.

hers a few pics of my tld66 install behind my glove box...where i swore there wasnt room...but with vw337's help....made room by moving one of my ecu modules

Post by **AVICJR** » Tue Apr 15, 2008 12:12 pm

That's exactly how I installed my LD's. Set it and forget it, it doesn't have to be on display.

My only knock against the TLD66 is that the power inputs are on the opposite side of the RCA connections. This made it a little more difficult in squeezing it behind the HU.

Post by **Bfowler** » Tue Apr 15, 2008 12:23 pm

yeah...that was sort of a pain

Stereo Junkie · Post by **Stereo Junkie** » Fri Apr 25, 2008 1:52 pm

stipud wrote:The main purpose of a high voltage signal is noise rejection.

A car is an electronically noisy environment, especially considering the number of gizmos, and how your entire chassis is used as a conductor. Big fat power cables, electrical switches, motors, etc will all give off electrical interference.

Now, let's say you have a 0.2v hypothetical noise spike, being radiated into your RCAs as they run along your chassis. Assuming you have a 1 volt RCA being passed to the rear, this 0.2 volt spike would be a whopping 20% of your signal voltage, so you will hear it very clearly with your amp gains set for 1 volt. On an 8 volt signal, that same 0.2v spike is only 2.5% of the signal voltage, so it will be MUCH less audible than the noise spike at 1 volt.

Now with your line driver situated in the rear, the noise spike will occur closer to the front of the car. If this happens, the line driver will amplify the 0.2v noise to 1.6v, where it will still be 20% of the 8 volt input signal. As such, this is really no different than running the 1 volt signal. In fact, having more items in your chain will only add more noise, so any theoretical advantages might be lost.

So yeah... the main purpose of linedrivers is to boost the signal up front, so it can make the dangerous journey to the rear of the car, and be less affected by radiant noise.

Stipud,

Wouldn't that be assuming the noise was coming directly from the head unit and not the the wiring between the head unit and the amplifier? Most noise I have occurred over my years has been picked up by a ground loop or running power lines next to the RCA's etc. Perhaps you can clarify this for me.

Thanks,
Stereo Junkie

Post by **stipud** » Fri Apr 25, 2008 1:59 pm

Stereo Junkie wrote:Stipud,

Wouldn't that be assuming the noise was coming directly from the head unit and not the the wiring between the head unit and the amplifier? Most noise I have occurred over my years has been picked up by a ground loop or running power lines next to the RCA's etc. Perhaps you can clarify this for me.

Thanks,
Stereo Junkie

My post was made with the assumption that the noise occurred between the headunit and the back of the car (thus, on the RCAs). If your noise occurs at the headunit, before the RCAs, even if you have only 1" of cable between your HU and RCAs, the linedriver it will still amplify the noise, and your noisefloor won't be reduced. In this case, you would have to fix the problem with the headunit, and no linedriver would solve the noise.

As you said though, mist noise will be picked up through the RCAs as they travel to the back of the car. This is why you want to have the linedriver as close to the front as possible, in order to have the highest signal voltage along your RCA runs. This will reduce the effect of radiated noise on your RCAs, since their voltage will be much higher than the radiation.

Stereo Junkie · Post by **Stereo Junkie** » Fri Apr 25, 2008 2:04 pm

In that case I might pick up a TLD66 soon....

Post by **stipud** » Fri Apr 25, 2008 2:27 pm

Even more important than a linedriver is proper installation.

Use this FAQ to see how you can eradicate noise from your system, before you even need to consider a linedriver. I would only add one once these checks have all been exhausted.

http://phoenixphorum.com/trouble-shooti ... vt178.html