Line driver or not

[allmet33]

I've seen a few threads on here where folks have had issues with their Xenon amps. I have read some that say they have to turn their gain up to like 3/4 before everything sounds the way they want it. Of course, I know the voltage output on the HU RCA outputs determine what the gain setting should be at, but...if one is using an HU with voltage output of 2 volts (such as my Pioneer), would the performance of my amp benefit from installing the SLD44 I have?

From my understanding, it would increase the signal voltage before it goes into the amp, therefore requiring less of the amp in terms of producing the signal on the back end. Essentially...I would be able to get the same performance an not have to turn the gain up. Is this information correct?

Initially I bought the SLD44 to integrate an aftermarket amp into the factory system in my '07 Outlook.

[fuzzysnuggleduck]

Yeah, you're pretty much right on.

You can think of a line driver similarly to the pre-amp in an amplifier. If you turn up a line driver, your pre amp (gain stage) has to do less work.

With the Xenons, I would think more than 2V would be good.

Edit: as below Brett is right, lower gains don't make you amp work less "hard". They make the pre-amp section of your amp do less. The power amp still does the same work.

[bretti_kivi]

not quite true; the amp still has to "work hard" to produce the output, but as it starts with a larger signal, it doesn't have to be pushed towards its limits to do that.
You're making the amp's life easier and also (probably) increasing the max volume you can get out of the system - if I take mine, I was running the amps in the garage with the gain wound round to 3 o'clock, just to get reasonable levels, because it's only a carPC.

Higher input signals also mean less audible interference.

Yep, I will be ordering a TLD-66 shortly

Bret

[allmet33]

Yeah, you're pretty much right on.

You can think of a line driver similarly to the pre-amp in an amplifier. If you turn up a line driver, your pre amp (gain stage) has to do less work.

With the Xenons, I would think more than 2V would be good.

So...the 2 volts that my HU is producing is at the low end of what I would really want, right?

If that's the case...I'll just have to install it and see what happens!

Here's another question...I understand how to set the gain to match the HU output, do I do the same thing once I install the SLD44???

[fuzzysnuggleduck]

Yeah, you're pretty much right on.

You can think of a line driver similarly to the pre-amp in an amplifier. If you turn up a line driver, your pre amp (gain stage) has to do less work.

With the Xenons, I would think more than 2V would be good.

So...the 2 volts that my HU is producing is at the low end of what I would really want, right?

If that's the case...I'll just have to install it and see what happens!

Here's another question...I understand how to set the gain to match the HU output, do I do the same thing once I install the SLD44???

2V will work, but you may want a line driver anyways.

As for gain setting with a DMM, yeah it's the same, just remember to set your LD gain with the same method.

[allmet33]

not quite true; the amp still has to "work hard" to produce the output, but as it starts with a larger signal, it doesn't have to be pushed towards its limits to do that.
You're making the amp's life easier and also (probably) increasing the max volume you can get out of the system - if I take mine, I was running the amps in the garage with the gain wound round to 3 o'clock, just to get reasonable levels, because it's only a carPC.

Higher input signals also mean less audible interference.

Yep, I will be ordering a TLD-66 shortly

Bret

Gotcha...so basically, the performance of my amp will be enhanced by installing the SLD44 and probably help the amp live a longer, happier life too, huh?

[Rold Gold]

yep...........

[allmet33]

yep...........

Cool...I'll take care of that when i redo my sub enclosure & amp rack!!!

Thanks a lot for all the input!!!

[Rold Gold]

Check out the "auctions" threads. There is a TLD66 on the bay for $45.....

[allmet33]

Check out the "auctions" threads. There is a TLD66 on the bay for $45.....

I may jump on one when I do the sytem in my Outlook. Good lookin out!

[thedeal7235]

i may not do some things right, like blow tweets, etc., but IVE always ran a line driver, from the old pld-1s to the newer sld-44, youll be glad u did , and ur amps may live a bit longer-imho, it also helps to clean the signal up some time, kinda like the tbas do

[allmet33]

i may not do some things right, like blow tweets, etc., but IVE always ran a line driver, from the old pld-1s to the newer sld-44, youll be glad u did , and ur amps may live a bit longer-imho, it also helps to clean the signal up some time, kinda like the tbas do

Many thanks for the feedback. I've got a few projects to look forward to when the weather is a bit warmer. So for now...I'll just get all my plans down so I can jump on them when the time comes.

[mrblack]

Alot of the info posted in this topic is quite misleading.

Lets start with the basic function of a line driver. When used in a correct application it will result in a lowered noise floor and hotter signal arriving at the amp. And yes, if you look at it from the skewed perspective presented in the earlier posts, it may take a bit of the work load off of the preamp section of an amp, but it will NOT make the amp work any less hard or generate any less heat to achieve the same output level as it would when driven without using a line driver. In most cases the result is exactly the opposite!

Line drivers are often used improperly when used with amps that have their gains set too high. The result of having your gains turned up may sound better and brighter to your ears in the immediate and until ear fatigue sets in, but in truth your signal will be driven to clip sooner, and your amp will overheat faster since it is being forced to work harder than it was ever intended to. And I've never heard of an amplifier burning itself out because the preamp section was receiving a signal that wasn't hot enough. The output stage of an amp does the most work and generates the most heat and therefore this is where problems most often arise. (which again is usually the result of an amp that has been pushed too hard)

Before you decide to get a line driver, you should ask yourself these questions:

Does your source unit have a lower than normal output level (if your unit is in fact 2Vrms, that should be more than enough to push your amp to its limits)
Are you running the signal over a longer than normal distance (>12ft)
Do you have to turn your gains all the way up to attain a reasonable volume level (when your amp starts to distort, it has already reached its output ceiling. A line driver won't fix this problem, only a bigger amp will)
Do you have audible background noise in your system due to having to set your gains too high (keep in mind there are many reasons that background noise may be present, this most often has to do with the preamp section built into your head unit. The use of a line driver will actually boost your noise levels in this situation!)

Unless one of those scenarios jump out at you as a major issue you're encountering, a line driver will likely be more than just a waste of money. If used improperly it could also cause your amp and possibly your speakers to fail sooner than you expected.

[fuzzysnuggleduck]

Good information.

I'm wondering however about the "improper" use you're talking about... is that in reference to driving your amp too hard and thus into clipping?

[stipud]

Hmm... I only saw one post with conflicting info (bretti_kivi). In fact in the second post fuzzy stated your exact point...

Edit: as below Brett is right, lower gains don't make you amp work less "hard". They make the pre-amp section of your amp do less. The power amp still does the same work.

Anyways, what mrblack is talking about is the usual misunderstanding about linedrivers. People install them to boost their signal voltage, but do not adjust the gains down... and all of a sudden their amp is in clip city. They think it sounds better because it is louder now.

Just to reiterate,
- A linedriver, properly installed, should not make your system "louder" - your gains should match the output level of the amp, regardless of the input voltage.
- A linedriver, properly installed, should be as close to the headunit as possible, so that it can offer greater noise rejection. Installing it in the back of the car next to the amp will amplify any radiated noise and defeat the purpose of having one.
- A linedriver does exactly the same thing as the preamp section of your amp. It's just a little chip op-amp that boosts your signal voltage.

So let's take PG's amps for comparison. Their output sections are designed for 8 volts input. However, most headunits don't come anywhere near this, so they have to add a preamp as well. This boosts whatever voltage input signal to 8 volts, so that the amp can reproduce the frequencies as if they were 8 volts straight in.

Another comparison... since the ZPA was a super-SQ amp, PG opted to remove the pre-amp, and forced you to use an external pre-amp (line-driver) instead.

[marko]

Another comparison... since the ZPA was a super-SQ amp, PG opted to remove the pre-amp, and forced you to use an external pre-amp (line-driver) instead.

this always confuses me, i know the zpa's don't have a preamp but they do have gains, so how do the gaind work in the zpa's

[mrblack]

I found these sets of comments the most misleading if taken at face value...

Originally posted by bretti_kivi
it starts with a larger signal, it doesn't have to be pushed towards its limits to do that.
You're making the amp's life easier and also (probably) increasing the max volume you can get out of the system

I disagree with most of the above. Ok, so yes the amp starts with a hotter signal at its inputs, but if set correctly, the signal that arrives at and travels through the output section of the amp should not be any hotter than it would have been without the use of a line driver.

Originally posted by allmet33
so basically, the performance of my amp will be enhanced by installing the SLD44 and probably help the amp live a longer, happier life too, huh?

Originally posted by FuzzyHoNutz
yep...........

Right here it shows that allmet33 misunderstood the true purpose of a line driver and took the comments that were made the wrong way. For those of us sharing our knowledge, we need to make sure we're careful to put it into a context that is factual and with integrity. A special thanks to Stipud for further clarifying what I was trying to say in my previous post.

Originally posted by thedeal7235
... but IVE always ran a line driver...youll be glad u did , and ur amps may live a bit longer-imho, it also helps to clean the signal up some time, kinda like the tbas do

I don't believe that the correct use of a line driver will in any way extend the life of an amp. A basic line driver only boosts a signal, it has no magic processing built in to clean it up. In fact, as a general rule the less equipment a signal has to travel through to reach its destination the cleaner the signal will remain. A line driver can however help keep the signal clean under the right conditions.

Over the years I've met many people who felt they understood what went on under the covers of their stereo equipment. The least knowledgeable of those are usually the most vocal when it comes to telling others what they NEED to do to get great sound out of their system. The average member here seems to be a little more knowledgeable and open minded than the rest out there. That's a big reason why I stop by here from time to time. But posts like this can be poisonous to newcomers, since a number of people might stop by and read this much like allmet33 did and take it the wrong way, and then go on down the road and repeat what he learned here. We just have to remember to be careful with what we post and how we post it.

I don't mean to be rude, but I'm probably coming off that way. I'll just go back and lurk a bit more till next time. Long live PG, and please bring back the forums!

[stipud]

this always confuses me, i know the zpa's don't have a preamp but they do have gains, so how do the gaind work in the zpa's

Do they? Perhaps they do have pre-amps after all, and they just require higher voltage. Hmm... makes you wonder why they would do that, and not put in one that's good down to 0.2V like normal.

I'll have to look into that some more.

[stipud]

Over the years I've met many people who felt they understood what went on under the covers of their stereo equipment. The least knowledgeable of those are usually the most vocal when it comes to telling others what they NEED to do to get great sound out of their system. The average member here seems to be a little more knowledgeable and open minded than the rest out there. That's a big reason why I stop by here from time to time. But posts like this can be poisonous to newcomers, since a number of people might stop by and read this much like allmet33 did and take it the wrong way, and then go on down the road and repeat what he learned here. We just have to remember to be careful with what we post and how we post it.

I don't mean to be rude, but I'm probably coming off that way. I'll just go back and lurk a bit more till next time. Long live PG, and please bring back the forums!

Ah, now that you point those comments out I see what you mean. I believe your assumptions were correct, and this thread was indeed leading allmet astray. As for going back to lurking, don't even think of it . If you hadn't piped up, we might've never fixed the miscommunication.

It seems that every time things like linedrivers or capacitors come up, regardless of the forum, there are always hundreds of people lining up to tell you the wrong way to use them

Perhaps I should make a topic in the How-To/FAQ section about them.

[allmet33]

Mrblack...my understanding after reading the posts was that the line driver can help lower the signal floor by increasing the signal voltage. I understood this to mean that instead of setting the amp based on the 2 volt output from my head unit, I would set the input sensitivity to match the output after the line driver. So if the output using the line driver turned out to be 8 volts, then I would set the gain to match that instead of 2 volts.

Now, correct me if I'm wrong...600 watts is 600 watts regardless of what the signal voltage is from the source, right? From my understanding, cranking the gain up doesn't necessarily make the amp work harder, but it surely abuses your sub(s) because you could potentially be sending an amplified dirty signal to them and if the gains are set incorrectly...clipping is more likely to happen, right? The use of the line driver lowers the signal floor creating a cleaner signal going to the amp, right?

Maybe these questions are dumb, but I'm asking based on what I understand. So if my understanding is incorrect...please let me know.

I'm also glad it was posted that you should install the line driver as close to the head unit as possible because I sure 'nuff would have put it in the rear with the amp somewhere.

See...this thread has helped me already!!!

P.S. Speaking of caps...what IS the proper way for them to be used??? I've heard both arguments that they are a waste of time and money and yet everywhere I look...I see installs using them like they are a necessity.

[bretti_kivi]

what you NEED to get great sound? Sound insulation, decent installation, and a good idea of what you want. An understanding of some of the basic principles...and math.

However, that's straying

Anyway, yes, the post I made is incorrect in some aspects and I was assuming quite a lot (which appears to have been justified, even if that was "lucky").


so, something like this could be considered to be correct:

Why use a line driver? Let's use a PA amp as an example. There's normally no "volume" control on those; they just amplify whatever is thrown at them. So, if you create a larger signal, you'll get a louder output, to a certain point. If you're putting in something that's bigger than design, then you'll (probably) get distortion and clipping and fried voice coils.

Conversely, if your signal isn't as large as the amp was designed for, you won't get all you could out.

Junk in, junk out applies here, too: you might be amplifying noise instead of music. Line drivers can help by increasing the output of a source, and then you should also turn your amplifier gains down to match. A Line driver shouldn't make your system "louder", though it may make the power of the amplifier accessible in a way it wasn't before. They should also be installed close to the source, as that way the more important input connections can be short and that means less chance for interference. The outputs are more resistant to noise.

As an aside, class D amps work on a slightly different variation of the same fundamental idea as the PA amps mentioned above. They have a fixed voltage and apply it for a proportion of time - so if it's a 0dB signal, the output is permanently on, but if it's only 25%, the "on" pulses are 1/3 the size of the "off" ones. Averages out to 25% voltage output: ___-___-___-___ .This is called "pulse width modulation".

comments?

Bret

[allmet33]

what you NEED to get great sound? Sound insulation, decent installation, and a good idea of what you want. An understanding of some of the basic principles...and math.

However, that's straying

Anyway, yes, the post I made is incorrect in some aspects and I was assuming quite a lot (which appears to have been justified, even if that was "lucky").


so, something like this could be considered to be correct:

Why use a line driver? Let's use a PA amp as an example. There's normally no "volume" control on those; they just amplify whatever is thrown at them. So, if you create a larger signal, you'll get a louder output, to a certain point. If you're putting in something that's bigger than design, then you'll (probably) get distortion and clipping and fried voice coils.

Conversely, if your signal isn't as large as the amp was designed for, you won't get all you could out.

Junk in, junk out applies here, too: you might be amplifying noise instead of music. Line drivers can help by increasing the output of a source, and then you should also turn your amplifier gains down to match. A Line driver shouldn't make your system "louder", though it may make the power of the amplifier accessible in a way it wasn't before. They should also be installed close to the source, as that way the more important input connections can be short and that means less chance for interference. The outputs are more resistant to noise.

As an aside, class D amps work on a slightly different variation of the same fundamental idea as the PA amps mentioned above. They have a fixed voltage and apply it for a proportion of time - so if it's a 0dB signal, the output is permanently on, but if it's only 25%, the "on" pulses are 1/3 the size of the "off" ones. Averages out to 25% voltage output: ___-___-___-___ .This is called "pulse width modulation".

comments?

Bret

I believe I have a better than decent installation, I'll be adding sound insulation for sure and I'm pretty close to arriving at the sound I want. I guess I'm here to ultimately understand what it is I'm doing, why I'm doing it and what the end result of my actions should be.

I've always done factory replacement systems, you know...systems that are just upgrades of what was in there before. What I have now is my stepping stone to creating a high quality sound system for my listening enjoyment. I say stepping stone because I am understanding that there are better components out there that I can be using. I'm learning that there is a lot more to it than just slapping it in your car and cranking the tunes. There is a science to the madness and that is what I'm trying to get an understanding of.

I do get what you're saying. Let me clarify this one thing...I never expected the line driver to make my subs play louder. From everything I've read or heard, nothing ever suggested (to me) that it would increase the loudness of my subs. My understanding was that the line driver would clean up the signal and lower my chances of pushing a dirty signal to the amp, therefore lowering my chances of worrying about clipping.

[stipud]

Mrblack...my understanding after reading the posts was that the line driver can help lower the signal floor by increasing the signal voltage. I understood this to mean that instead of setting the amp based on the 2 volt output from my head unit, I would set the input sensitivity to match the output after the line driver. So if the output using the line driver turned out to be 8 volts, then I would set the gain to match that instead of 2 volts.

Bingo.

Assume you're running a 2 volt signal on your RCAs. Let's say there's a 0.2v radiated noise coming from your car, as the RCA runs from the front to the back. At 2 volts, that 0.2v noise is 10% of the signal, and it would result in a very audible background hiss at lower volumes or between songs. However, at 8 volts, that 0.2v noise is only 2.5% of the signal, so it will be much less audible.

This becomes much more important when you consider how fake headunit voltage ratings are. Most people know that a "55x4" headunit will produce closer to 10x4. Same goes for the RCAs. Most "2v" headunits i've tested are lucky to make 1v RMS, and even expensive 4v Alpines are lucky to make 2v.

The linedriver needs to be installed next to the headunit, since the high signal voltage is used to minimize the amount of radiated noise on the RCAs as they travel to the back. If the signal was 2v from front to back, and the linedriver was installed in the rear, it would amplify the noise and you would be no better off than without it.

Now, correct me if I'm wrong...600 watts is 600 watts regardless of what the signal voltage is from the source, right? From my understanding, cranking the gain up doesn't necessarily make the amp work harder, but it surely abuses your sub(s) because you could potentially be sending an amplified dirty signal to them and if the gains are set incorrectly...clipping is more likely to happen, right? The use of the line driver lowers the signal floor creating a cleaner signal going to the amp, right?

Assuming the gains were properly set, you will get 600 watts out of your amp regardless if the input voltage is 2v or 8v. That is the point of the gain knob -- to match your input voltage to the amps output voltage.

To properly set your gains, you can do it with a multimeter and a test tone:
http://phoenixphorum.com/gain-setting-w ... vt280.html

Now assuming you have your gains turned higher than necessary... your amp will clip on louder notes. This is not good, because it damages the amp and possibly your speakers as well.

Maybe these questions are dumb, but I'm asking based on what I understand. So if my understanding is incorrect...please let me know.

I'm also glad it was posted that you should install the line driver as close to the head unit as possible because I sure 'nuff would have put it in the rear with the amp somewhere.

See...this thread has helped me already!!!

The only dumb questions are the unasked ones.

P.S. Speaking of caps...what IS the proper way for them to be used??? I've heard both arguments that they are a waste of time and money and yet everywhere I look...I see installs using them like they are a necessity.

Caps are a great addition to any adequate power system. The wrong way to use them is as a bandaid for an inadequate power system, which is unfortunately the most common thing I hear about them.

The common incorrect school of thought is, if you have headlights flashing... add a cap. Because a cap acts as a power storage device, so it will store power in between bass hits, and unloads that power during them. This is BS because a capacitor will be unloaded within milliseconds, assuming your power distribution (e.g. alternator, battery) can't support the current draw. In this case, a capacitor only makes things worse, because it acts as a current draw on a system (since it also has to recharge), and only reduces the amount of current available for the amp.

Much more important is ensuring your power distribution is adequate. Most people's installs have fat 0 gauge coming off the power terminal, but they leave their shitty 10 gauge factory ground in place. Obviously, you need to upgrade your battery ground to 0 gauge as well, otherwise you are forcing all of your system's current through that tiny 10 gauge wire. Also, there is a benefit to upgrading your alternator to battery connection to at least 4 gauge as well... and it can be beneficial for your engine's performance to ground to the engine block to the battery with 4 gauge too

A capacitor's usefulness as a power storage is minimal. What makes capacitors useful is that they act as an A/C ripple filter. Your alternator does not provide pure, clean D/C current due to the way it creates power. An alternator actually creates many A/C waves a few steps out of phase from each other, and then uses a big rectifier diode to cut the tops off of the A/C waves, and sum them into D/C voltage. However, there is still some A/C ripple left in the signal (it's not perfectly flat D/C).

The amplifier's power supply doesn't like A/C ripple. This is why the input on amps have capacitors... to filter out A/C ripple. Otherwise the amps would not run stable whatsoever, and would likely shut down all the time. However, the input capacitance in amps is typically very low, and you can achieve additional filtering by adding a capacitor. This results in a cleaner sounding setup... assuming your gear and install is good enough to hear the difference. Things like sound deadening are likely way more important to do first, in order to even hear a difference.

Also, when using a capacitor, you want to use it for all your amps... not just the bass amp. Also, any more than 2 farads is overkill in any setup. Most of the larger capacitors have lower ESR (Equivalent Series Resistance), which means they are worse at A/C ripple filtering. So if you decide to add a cap one day, look for a low ESR cap under 2 farads.

[allmet33]

Bingo.

Assume you're running a 2 volt signal on your RCAs. Let's say there's a 0.2v radiated noise coming from your car, as the RCA runs from the front to the back. At 2 volts, that 0.2v noise is 10% of the signal, and it would result in a very audible background hiss at lower volumes or between songs. However, at 8 volts, that 0.2v noise is only 2.5% of the signal, so it will be much less audible.

This becomes much more important when you consider how fake headunit voltage ratings are. Most people know that a "55x4" headunit will produce closer to 10x4. Same goes for the RCAs. Most "2v" headunits i've tested are lucky to make 1v RMS, and even expensive 4v Alpines are lucky to make 2v.

The linedriver needs to be installed next to the headunit, since the high signal voltage is used to minimize the amount of radiated noise on the RCAs as they travel to the back. If the signal was 2v from front to back, and the linedriver was installed in the rear, it would amplify the noise and you would be no better off than without it.

Okay...got that! As far as wattage output of h/u's...I've never paid attention to the max power, always look for the rms numbers. I learned that lesson early on. However, I was not aware of the voltage output on the RCA's being the same way. I guess I could use a DMM to measure the voltage output of the RCA's on my h/u, right?

Assuming the gains were properly set, you will get 600 watts out of your amp regardless if the input voltage is 2v or 8v. That is the point of the gain knob -- to match your input voltage to the amps output voltage.

To properly set your gains, you can do it with a multimeter and a test tone:
http://phoenixphorum.com/gain-setting-w ... vt280.html

Now assuming you have your gains turned higher than necessary... your amp will clip on louder notes. This is not good, because it damages the amp and possibly your speakers as well.

Understood.

Caps are a great addition to any adequate power system. The wrong way to use them is as a bandaid for an inadequate power system, which is unfortunately the most common thing I hear about them.

Yeah...initially my interest in a cap came from the whole headlight dimming issue, but come to find out...I was working with a crappy battery to begin with. When I replaced the factory battery with a new one...the dimming went away. However, after reading what you posted, it would seem that my amp would actually benefit from me keeping the cap in place so it can filter the A/C ripple and provide the amp with a closer to D/C type current it prefers, correct? Now...as far as using the cap on all the amps, the OEM amp isn't running off the cap, just the sub amp. If I were to install an aftermarket amp to run everything on the inside...I would run it off the cap for sure.

As far as the grounds, I always understood that the gauge of your ground wire should be the same gauge as your power wire.

[stipud]

attention to the max power, always look for the rms numbers. I learned that lesson early on. However, I was not aware of the voltage output on the RCA's being the same way. I guess I could use a DMM to measure the voltage output of the RCA's on my h/u, right?

That's right. Just follow the DMM link I posted above, and instead of testing on the + - speaker leads, you test between the RCA pole (+) and shield (-). That will give you the RMS voltage of your RCAs.

Yeah...initially my interest in a cap came from the whole headlight dimming issue, but come to find out...I was working with a crappy battery to begin with. When I replaced the factory battery with a new one...the dimming went away. However, after reading what you posted, it would seem that my amp would actually benefit from me keeping the cap in place so it can filter the A/C ripple and provide the amp with a closer to D/C type current it prefers, correct? Now...as far as using the cap on all the amps, the OEM amp isn't running off the cap, just the sub amp. If I were to install an aftermarket amp to run everything on the inside...I would run it off the cap for sure.

As far as the grounds, I always understood that the gauge of your ground wire should be the same gauge as your power wire.

You got it!