question about line drivers

deathcloud · Post by **deathcloud** » Sun Sep 28, 2008 10:47 pm

So I have now purchased a SLD-44 and PLD-1 line drivers

I was going to have my SLD-44 plugged into my Xenon 200.4 front/rear inputs which it says 11volts and I think I read somewhere that bfowler has it at 11 volts and it doesn't have any problems. I tried reading the manual and it doesn't really say the maximum input voltage like it does for my RSD600.1 which is 10volts.

My second question is if I use my PLD-1 for the RSD 600.1 then it should be fine right? 8 volts send to my RSD 600.1 should be really nice.

I am getting super excited for all my goodies to come.

maka78 · Post by **maka78** » Mon Sep 29, 2008 7:19 am

Although I haven't tried putting a line driver in my setup yet, I'm pretty sure it goes something like this:

The line driver will make you turn down your gain. If you have an amp that accepts a voltage that's less than the input voltage of the line driver, then your gain will be all the way down and you will still end up clipping. What I would is check your output with a DMM (check the how-to section). If your amp is clipping with the gain all the way down and your HU on 3/4 volume, then turn your HU down a bit more until the clipping goes away.

Someone who has more experience on this topic than me correct me on this, but I believe your HU volume knob is what controls what the HU output RCA voltage is, which determins what the line driver input voltage is, what determines what the line driver output voltage is, which in the end, determines what the amplifier RCA input voltages is. Again, I'd wanna check this and confirm (since I don't have a line driver and haven't proven this theory myself).

Post by **Bfowler** » Mon Sep 29, 2008 7:47 am

i'm sending my xenon's just a hair over 10, but 11 will be fine, they can easily take up to 13.

Post by **fuzzysnuggleduck** » Mon Sep 29, 2008 8:57 am

Remember, music is dynamic. Saying "I'm feeding my amp 10V from the line driver" really means "the most my amp will ever see during the highest musical peak is 10V from the line driver".

You can apply the same method to gain setting your amp to setting your line driver's output voltage.

Post by **Bfowler** » Mon Sep 29, 2008 9:12 am

true^

but that still drastically more then "the most my amp will ever see is 4volts out of my kenwood"

Post by **fuzzysnuggleduck** » Mon Sep 29, 2008 9:18 am

Bfowler wrote:true^

but that still drastically more then "the most my amp will ever see is 4volts out of my kenwood"

Certainly!

Post by **stipud** » Mon Sep 29, 2008 9:20 am

The best way to set linedriver gains is to lower your amp gains to a minimum. Then play a 60Hz test tone, and increase your line driver gains until you reach the desired voltage AT THE AMPLIFIER. However, you must ensure that the linedriver doesn't clip the signal either. If it does, turn the linedriver down, and increase the AMP gains until you get your desired voltage.

Alternatively you can do as fuzzysnuggleduck suggested. With the amp disconnected, connect your multimeter probes to the RCA pole + and shield -. Increase the linedriver gains until you see the voltage you want, or until it clips (most LDs have a light for this).

maka78 · Post by **maka78** » Mon Sep 29, 2008 10:02 am

What is the point of a line driver exactly? If an amplifier accepts .2-8V input, and your HU is outputting .283V (as in my eclipse), then you should be fine, correct?

You would set the gain relatively high on the amp, but I feel like this is equivalent to setting the gain at its lowest on the amp and boosting the signal on the line driver.

Are there any advantages to having the line driver do the boosting over your amp?

Post by **fuzzysnuggleduck** » Mon Sep 29, 2008 10:11 am

maka78 wrote:What is the point of a line driver exactly? If an amplifier accepts .2-8V input, and your HU is outputting .283V (as in my eclipse), then you should be fine, correct?

You would set the gain relatively high on the amp, but I feel like this is equivalent to setting the gain at its lowest on the amp and boosting the signal on the line driver.

Are there any advantages to having the line driver do the boosting over your amp?

It raises your noise floor as the signal travels down the RCA pair. It basically makes your signal to noise ratio much higher for the transport section of your signal chain.

Post by **stipud** » Mon Sep 29, 2008 10:15 am

Bingo. Lets say you have a 250mV noise hitting a 1V RCA. That 250mV noise would be 25% of the 1V signal. At 8v, it's only 3%. So by having a higher RCA voltage, your signal is less affected by radiated noise.

Play a 0dB track through your stereo (aka a totally quiet signal) and turn up the volume all the way. If you hear hissing, this is your "noisefloor". A linedriver will typically reduce this background hissing substantially, assuming it is installed correctly. That is, it has to be installed UP FRONT, where it actually does its job. Installing a linedriver in the back of a car completely defeats the purpose, since there will be very little noise inducted in the last foot or two before your amp.

maka78 · Post by **maka78** » Mon Sep 29, 2008 10:20 am

fuzzysnuggleduck wrote: It raises your noise floor as the signal travels down the RCA pair. It basically makes your signal to noise ratio much higher for the transport section of your signal chain.

So would it be better to have the line driver closer to your HU, amp, or in the middle?

From what you're saying, it'd be better to have it right out of the HU, without an extra set of RCAs.

Post by **stipud** » Mon Sep 29, 2008 10:32 am

maka78 wrote:So would it be better to have the line driver closer to your HU, amp, or in the middle?

From what you're saying, it'd be better to have it right out of the HU, without an extra set of RCAs.

Yep. The ideal situation would be 8 volts RMS straight out of the headunit. Unfortunately I have yet to find an "8 volt" headunit that actually puts out that much power.

deathcloud · Post by **deathcloud** » Mon Sep 29, 2008 10:36 am

Well thats the thing. Some people like thedeal7235 have their line drivers in the rear of the car for example

however, if I mount my line driver in the rear, because it looks to be easier to do it that way, is there a disadvantage? Here is how I planned to install my line drivers for ease of installation. I dunno where I would install my line drivers cuz I would have to install two by the Headunit which would be fairly hard.

Post by **stipud** » Mon Sep 29, 2008 10:46 am

There's very little point in running a linedriver in the rear of the car, unless you have an amp like the ZPA that absolutely cannot run on headunit voltage. For a linedriver to be useful with your amps, they need to be installed up front.

Instead of a PLD and SLD, you could get a TLD66. This has 6 channels in a smallish box, and should be easier to install. Alternatively, just use the SLD and run two RCAs to the Xenon and RSD. The Xenon can take its rear inputs from the front channels.

deathcloud · Post by **deathcloud** » Mon Sep 29, 2008 10:52 am

Yea I was thinking of doing that too. I guess I will do that. Just try to find a place to install my SLD-44. Somewhere as close to the HU as possible...

Post by **fuzzysnuggleduck** » Mon Sep 29, 2008 10:52 am

Well, the disadvantage of running you LD in the back is that it's amplifying any noise the RCAs pickup. It'd be no worse than without the LD, but it certainly isn't doing much unless, as stipud said, your amp NEEDS high level input and you have nowhere else to install your LD.

deathcloud · Post by **deathcloud** » Mon Sep 29, 2008 10:54 am

I know the PLD-1 ups the voltage to 8volts and the SLD-44 ups it to 11volts but I was wondering what the TLD-66 ups the voltage to as it doesn't really say on the manual. anyone know?

I see your point about just putting it in the back vs up front by the HU where its supposed to do its job from there. Cool thanks for the info.

Post by **stipud** » Mon Sep 29, 2008 10:59 am

fuzzysnuggleduck wrote:It'd be no worse than without the LD

Actually, it can be. For every device you add in the signal chain, you increase noise. A linedriver installed properly will reduce way more noise than it will cause, but one installed in the back of the car may create more noise than if it weren't there.

All you are doing with a linedriver in the back is bypassing the amplifier's preamp and using the linedriver instead. This might still have a modest benefit if your linedriver has a better opamp than your amp's preamp. In this case it would do the 8 volt amplification better than your amp's preamp does. I heard the RSDs have very nice preamps, but there is room for improvement with the Xenons (whether or not a linedriver is better though, I do not know).

Deathcloud, there is usually lots of space behind the dash in cars. You just have to figure out where you can mount to. Removing the glove box is usually a great place to start, as it gives you much more access behind the dash. Alternatively, you can install it behind or even in your glovebox if there's absolutely no room.