Stereo Line Drivers

I'm pondering a Phoenix Gold Line Driver. I understand what it does and how it works. But what I'm wondering is why would I need it?

My head-unit puts out 2v on the RCA preamp outputs. I understand that this Line Driver would take the 2v and output an 8v signal. My amplifiers are about 20 feet from my head unit. It seems that EMI and RFI noise wouldn't effect the SQ output as much at an 8v signaling voltage verses 2v. (this would be nice for when someones cell phone starts chattering.) I'm not really having a problem with SQ (that my tin-ear is aware of.) The next benefit would be to overcome a voltage drop due to wire resistance from the 20 feet of RCA cable - I'm not sure how to approach evaluating wither or not this is a concern. Finally, it seems to me that if I were running multiple amplifiers and were supplying signal to them by simply splitting RCA's with 'Y' cables that I could use the line driver to overcome a voltage drop.

My questions:
1) Do I actually understand what these things do, based on my above description?

2) Why would someone install a line driver?

3) Those of you who use them, Why have you decided on them?

I ended up having to put a line driver (used Audio controls version) as well. I wanted to be able to control the volume Independently (one for the boat i.e. sub and components, and another for the tower speakers) of the clarion remote. I ran one 20ft RCA cable around the front of the boat to the driver side PAC-1 level control and then 20ft RCA all the way back to the amps. I originally tried it without the line driver and it was not loud enough, especially the tower. I removed the 40ft of RCA cables, using jumpers from the radio to the amps directly and it was MUCH louder. So after talking to clubmyke he suggested getting a line drive and it solved my problems. The HU outputs the maximum 2V with the radio turned all the way up, but the signal with the radio not cranked is much less. the line driver just helps the signal get all the way around and then still and adequate for the amps. I am very pleased with the outcome and now do not need to turn the radio all the way up to get the output I had expected form the JLamp and the wetsound speakers.

I hope this helps and if I can answer any more questions let me know.

Tim

So in that case you're using it to combat the attenuation caused by the resistance of a 40' RCA run. Makes sense.

Anyone else have experiences with Line Drivers?

Adam? Mikeski? Rod?

alright here goes......I have one built in to my clarion eq.....I don't think it really puts out the 7 volts it claims. They do work and you will really be able to tell a difference with and w/o one. Someone on here , I think PHM??? found a planet audio (mostly known for junk) that claimed 10 volts and he bench tested it and the thing really produces what it states (only cost liek $40). do a search for planet audio line driver and see what you find.

The way I understand is that you need to match your gains up to the output voltage of yoru HU. If your voltage on your HU is 2 volts you should not have your gains up all the way for optimal SQ, with a line driver your voltage is boosted and you can properly turn up your gains to match the new RCA voltage (hence the louder volume) Most non competition systems will just turn up the gains regarless (I do) but the line driver allows you to do it the right way.....the end result is louder volumes and theretically better SQ than before.

What most people end up doing though is keeping the gains where they were set (too high) and hook up the line driver and the result is alot more volume with the same SQ as before.

Another benefit to higher line voltage is less interference...similar to phone lines...they boost voltage for clearer calls.

I haven't used one yet, but I have been considering it.

I am surprised that anyone would need it for a connection between the head unit and the amp. I don't care how much wire you ran there couldn't be enough signal loss to require boosting the signal. The amps should have enough adjustment range to get full power output.

It is possible that an increased signal strength would make the wiring more immune to picking up noise. If the noise level stayed the same, but the signal was 4x you would effectively cut the noise out. On the other hand, I have had very bad luck powering anything off the boats electrical system that feeds the stereo. I can't even power my Ipod off the cigarette lighter wihtout getting noise. So it would be a question of which was the greater source of noise.

Where I want to use a line driver is on the INPUT to the head unit. When I connect my Ipod the music volume is way down, even when I have the Ipod cranked all the way up. I would like to install a line driver to bring the Ipod up to the same level as the receiver and CD player so it doesn't blast me out when I switch back from the Ipod.

or call audiocontrol and ask them

for a really nice overview on high voltage signals go to zapcos website and readup on symbilink.

for practical purposes ~longer cable = more capitance =frequency falloff as the cable lengthens..compound that with meager 2v preamp output stage of the clarion...the MOST it can put out is 2 volts..think of preamp voltage level as a low voltage amplifier.
trying to get a weak 2v signal through 40 feet of cable doesn't work to well...most the time a high voltage balanced signal for long runs since the noise from the high voltage gain will be cancelled ....since most systems are not balanced the next best thing is to add a line driver to overcome the capitance of the cable and not to mention to match the input gain of the amp...

if you don't want to add one..you don't have too..

if you find you have to turn up the gains of your amp to compensate for the low level (this is really bad for the amp since the output stage is being overworked to compensate for the low input)

btw, forgot to mention noise..

(Message edited by clubmyke on August 24, 2006)

I bought the AudioControl Three.1 and love it. It boosts the line voltage, has master volume control, sub amp controls (gain and sweep), fader knob for the tower speaker amps, and 3 band equalization all in one little unit. Works perfectly for my application.

Clubmyke explain to me how its bad for an amp to turn the gain up? Seems to me it was desgned to operate within those adjustments and I read that the higher the gain is set, on certain amps, all it does is increase the rate at which the output drivers increase their output? The amp consumes power based on its relative output/current not more just because the gains are turned up from my understanding of basic electronics? Overworking an amp is driving the output section into clipping where there isnt high enough voltage or the gains plus the relative input to the amp determine the output. I do understand though how a higher preamp voltage can be cleaner at lower settings because you WONT have to drive anywhere near the max to get a clean signal of optimum levels.

adam youre referring to psyclone(if im not mistaken he is an electrical engineer). he did mention the panet audio line driver and i picked one up based on his recommendation(mostly b/c i just run an mp3 player and no hu). anyway, its been about the best 40 bucks ive ever spent.

"Clubmyke explain to me how its bad for an amp to turn the gain up?"

depends how high..if within the amps parameters... no problem.. if too high it is kinda like driving a car at high rpm (7k) all the time whe the limit is 7.5k rpm.. can the car do it...yes... good for it... no..

"if you find you have to turn up the gains of your amp to compensate for the low level (this is really bad for the amp since the output stage is being overworked to compensate for the low input) "

most amps have 2 gain stages input gain stage(little gain) and a output stage(lots of gain)...if they are not matched (ie voltage and impedence).. to reach the desired output then both of the stages has to be increased. oversatuation (high input gain) or low input gain are equally bad. oversaturation will cause the amp to clip at low levels and undersaturation will cause the amp the clip at high levels.

if the input level is too low then the amp gains will have to be turned up(this turns up both input gain and output gain) by overpushing the output stage which produces the most power creates more heat and too huch heat leads to "generally" less output..

even with very high quality amps, excessive heat will lead to premature failure.

btw, the audiocontrol gear is very, very high quality gear and reasonably priced..


(Message edited by clubmyke on August 24, 2006)

Clubmyke,

"~longer cable = more capitance =frequency falloff as the cable lengthens"

Is it a correct statement to say that as the cable lengthens, low frequencies fall-off quicker than high frequencies? I assume this since the capacitance increases proportionally to cable length. Also, Is this different than attenuation, of which I assume attenuation to be the degradation of signal over distance, regardless of frequency?


Also,
"if you find you have to turn up the gains of your amp to compensate for the low level (this is really bad for the amp since the output stage is being overworked to compensate for the low input) "

I'm trying to understand this, this would be like setting the amp gain to 1.7v while the deck puts out 2v signal?



To sum, there isn't much advantage to a line driver, aside from noise, for short distance pre-amp runs? If I have a 2v HU signal, then I set the amps to 2v gain. If I ran a line driver, that increases the voltage to 8v, then I set the gain to 8v. (no benefit in SPL, as in this scope SPL is a product of wattage output and has little to do with GAIN adjustment after it's been setup correctly.)

In the past I've had problems with clipping, regardless of what I set the gain to, when I use an RCA-Y splitter to split the signal to multiple amps. Would a line driver benefit to where I could run a RCA-Y splitter?

Alan Plotz -
Is this the one you're talking about?

http://cgi.ebay.com/PLANET-AUDIO-6CH-LINE-DRIVER-6-CHANNEL-NEW_W0QQitemZ120024601179QQihZ002QQcategoryZ14932Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

Craig like I mentioned earlier, not to many people have their gains set correctly, I know I don't, and have zero problems. you can analyze it a million different ways but at the end of the day adding a line driver to your system (all else the same) you will notice a significant difference.

I've been screwing with my gains for weeks and have found that the Skylon Rubicons are hyper sensitive to gain variations. The Rubicons have clipping protection in their passive cross-over. They attenuate the horns if they detect clipping. I think I'm pretty close to having my gains set correctly. (finally) After this exercise, I've learned that I've never had gains set correctly in the past.

So maybe the best bet is to just set theory aside and drop the 40 or 50 bucks to see for myself?

david yes thats it. you can find those online too for the same price or a little cheaper with more reasonable shipping

That Planet Audio line driver looks like it does not have a simple volume adjustment for each output.

For that, I would still probably need to use my LC1's, correct?

uhmmm... see what adam said..it is sooo true.

the best way to put this.. the speced 2v from these headunits is pretty much the worse preamp out stages to exist in mobile audio (ie the worse of the worse... sorry.. not to mention it is 2v at full output ie no headroom)...sometimes this is compounded by running attempting to run this through 40 feet of rca cable (ie pac controllers)... keep in mind since these are passive units the impedence will change dpending on where the volume knob is..this is also compunded by the capitance of the cable..

in regards to the amp input level... you are assuming it is a constant 2v... it is 2v at FULL OUTPUT given the quality of the topology of these decks (see above about the quality ) and that is if you believe the specs.. whay do you think SO many people who added one said they noticed a major improvement ?

which brings the question -what is the input sensitivity of your amp ? do you know ? chances are it is 4v-5v....so if you are attempting to run a poor quality 2v (at highest output) to a 4v-5v amp input your amp will get 1/2 power if your lucky (if through pac controllers about 1/3 with both volumes wide open)... which now leads to the question of the current capability of your amp.

if your amps are clipping then could one or a combination:

- poor quality amps
- not enough power to them (electrical system)
- gain set to high
- pre amp level set to low
- low sensitivity speakers
- amp power to low

y spilters are a really bad idea on cheap decks.. you are trying to ask the deck to double the voltage output into a lower impedence ( the preamp stage will clip and/or burn out)

there is a reason why the really,really high quality decks in the $1k up range (denons, clarion, macintosh, eclipse(good bang for the buck ) offer high voltage "balanced" outputs- it sounds better... i am using the eclipse 8053(the last of the 16v balanced eclipses running symbilink in the boat)very clear and no noise...

if you dont want to run a $$$$ balanced headunit then 8v-13v line driver like the audiocontrol is the next best thing(high quality output stage and allows for dynamic headroom)

(Message edited by clubmyke on August 25, 2006)

Hey Clubmyke - which Audiocontrol line driver do you like? Something like the Four.1, or the Matrix? Any other recommendations? Please be specific...lol

I'm getting a line driver soon for sure.

I have a Audio Control line driver. I have the Overdrive. I dont use it to drive my system. I use it to pass a signal from boat to boat.

Neither the audio control Matrix or the Planet Audio six channel line drivers have a front panel type volume adjustment. They have a gain adjustment, but it is meant to be a fixed adjustment after you set it up.

The AC 3.1 and 4.1 have two channels, or one stereo pair. It has knobs and front panel with EQ controls. THere are other manufacturers that make similar dash mount line drivers/EQs.

I needed three for what I want to do.
I tried to order the matrix three times online, no joy so I bought the cheap ass Planet Audio one. It works great and puts out like a cheerleader.

The Matrix and Planet Audio are underdash mount, like an amp.

I use a three channel volume control (PAC LC1 type but homemade, see my old post for details) on the output of the line driver to have independent control of the RCA inputs to my three amps, sub, tower, boat speakers.

19.5 ft is the magic length where cable capacitance starts making a noticeable difference. If you are going to use long RCAs, pay the extra money for good ones and use a line driver.

David - I use the Audiocontrol EQS it is attached a factory Clarion HU. It totally changed the quality of my system.

Psyclone,

Thanks for answering my question. I appreciate it.

david,

there are a couple... the eclipse 21010 and the audiocontrol 3.1 & 4.1 (btw, i spoke to the engineer at audiocontrol and they can make a resistor to run the sub control full range so you can use it on control your towers..pretty cool..wether the 3.1 or the 4.1 is a tough call.. alot will depend on how you configure your system... here is a really good checklist:

http://www.mobileaudiocontrol.com/dept.asp?d_id=5250&l1=5250

if using long interconnects i would be tempted to run a matrix right out the deck and over a 3.1 or 4.1 (one for getting there and the other to take it back)

(Message edited by clubmyke on August 26, 2006)

Okay Clubmyke - this is pretty random as far as the order of my questions but I have a few thoughts I was hoping you could comment on:

The 3.1 has sub controls and more outputs than the 4.1, but the 4.1 has an auxilary input (which the 3.1 doesn't have).
--Is there any product that I could get to have more outputs AND sub controls AND an aux input?
--Also, will the aux input on the unit help with the fact that I have an aux on my HU that basically sucks - namely, I have to turn the volume waaaay up compared to a CD when I use my iPod. Will the Aux on the 4.1 unit help with that problem?

Next, maybe you can help me out and make a recommendation based on my amp setup. And FYI - the main reason I want to get one of these is to add to the voltage that the amps are getting - my crappy Sony head unit is putting out 2 volts so that sucks - and have more control of the sound coming out of the tower speakers since I know they tend to sound a little bright right out of the box.

The other thing I don't get is how exactly to set one of these up with regard to the RCA plugs.
--If I have 4 amps (one 4 channel, one 2 channel, and two mono) that means I have 5 sets of RCA plugs and the line driver/EQ only has 2 ins and 3 outs (or something like that) how do you connect it all? I'm a little confused on this.

My setup is 2 500watt (mono) Memphis amps that are powering 2 Kicker S12L7 subs. And my third amp is a Memphis 55x4 that powers the interior speakers. I'm going to have a 4th amp in the next week or two, as I'm adding tower speakers - it will probably be the Arc Audio 2500xxk or the Massive Audio 800.4 - so I want to account for that as well.

Oh yeah, thanks for the help.

And one last thing - Greg posted above about the AudioControl EQS. I checked it out and it looks pretty sweet. Will that unit work as well as, or better than the Four.1 or Three.1 unit? Do you have any experience with the EQS or similar?

thanks again.

dave,

whoa....

what is your ic length you will run ?
why do you need separate control over the subs?
if so, does your sub amp have a volume control and crossover (most do)?
do you need crossovers ?
how many volume control zones do you need (sounds like 3)?
is the tower the only section you want to equalizè?
do any of the amps have rca 'outs' ?
could you go a zapco 750 instead of the arc? (symbilink~adds high voltage and volume control)...

if you want-send me your cell number and a good time to talk..

Your questions:

---The cable length is probably 12 feet max. I'm going from the HU down to the floor, and directly across the boat (under the walkthrough) to the observer seat storage. Not that far.

---I don't need separate control over the subs. I just thought it was a cool feature. As a matter of fact, my cheap Sony HU has sub controls on the deck.

---My sub amp has a crossover. It also has a volume control knob, but that's an option - I don't have the knob. No big deal though. I figure on the subs, once the gain is set, it's set and it's fine.

---I don't think I need crossovers. My mids/highs don't get worked that hard with the way my 4 channel amp is set up so I think it's dialed. I guess an external crossover would be more of a fine tuning, but I think it sounds pretty good as it's set right now. Although I'm sure there's always room for improvement.

---The only thing I think that would be nice to have for separate volume control would be the tower speakers. It's not necessary, but I can see where I might want to have them softer than the rest of the boat at one point or another. I don't see a reason to have 3 separate volume control areas unless having it was a by-product of the EQ/line driver I end up buying.

---Yes, the tower is what I want to equilize. Unless there is going to be an advantage to EQ'ing other areas, I'm only considering EQ'ing the tower speakers becuase Wet Sounds Pro80s are pretty bright to begin with, and I like music a little "rounder" so to speak.

--The mono amps have outs, and I'm pretty sure the 4-channel has outs too. I'll check the manual since the boat is in storage right now.

---I could go with the Zapco 1000 (not 750), but I've been told it won't work with the ohm load and 4 speakers. That's why I was going to go with the Arc or the Massive, and tonight, I found out that the Massive warranty is 1 year, but only if the charging system is a minimum 220 amp alternator. So the Massive might be out. I want to give the speakers 200-250 watts a piece, and I am assuming that I'll buy an amp that can accomodate powering 4 speakers, as I'll probably have 4 at some point. I'm undecided on that at this point, but was planning for 4.

Also, I just found out that Memphis just released a 125x4 amp, and I could probably go with that amp if I decided to only go with 2 speakers so it will match my other stuff. hmmmm.

Anyways, the point to having the line driver originally was to increase the voltage to my amps. If I can EQ the tower speakers in the meantime with the same unit, then that would be great. Other than that, it's all bells and whistles.

Lastly, I'm assuming that you wanted to know if my amps have outs because the way to hook up a line driver is to run one mono amp and 1 AB amp to the inputs, and then run them from the outputs to the amps, then run the outs from those amps to the other amps. Right?

oh and by the way, an aux on the unit would be nice (like the Four.1) since I use an iPod a lot and it sounds REAAAALLY soft coming out of the factory aux. I have to crank the volume and the bass way up to get close to the sound of a CD. I assume that being able to plug my iPod into the aux input of the line driver would be a big improvement over my existing scenario?

this is tough call assuming you have a remote for the deck..... most systems will use the fader to go between the boat system and the towers speakers..

lots if choices...dont worry about using a y-adpaters with these units, they can handle the lower impedence and voltage unlike the deck..

you could go with 2 units..you could add a 30 band eq in between the 4.1 and the tower amp..you could also go with the eclipse 21010...

i was thinking the zapco on the tower speakers... it has the symbilink which would allow for a seperate volume control...

in regards to the ipod, i dont know if the eclipse or the audiocontrol has a different voltage gain for that input (check out the eclipse 21010 too..nice unit) you might have to add a seperate 2 channel line driver for that..

I had the eclipse 21010 its a great (Non-powerd) or passive eq. Another nice EQ is the PPI par-650

Aslo if your looking for a Line Driver Ill sell you my Audio control overdrive

Alright. Well, I still don't know what to do, but I guess I have some stuff to think about now.

thanks for the help Clubmyke.

grant thanks for catching that... i wasnt aware of it (eclipse is very good and looks good on paper)..

clubmyke,

I understand analog signaling to some degree, and understand that 2v represents the max, or peek of the wave.

So after re-reading this thread tonight, I pondered the significances of the 2v signaling. Please verify if my logic is correct...(sorry guys, I get rather detail oriented and like to thoroughly understand the theory behind stuff)

At a 2v signal strength, when you turn the volume from max down 3db, the max signal then becomes 1v, down another 3db it becomes .5v, one more 3db .25v, and so on logarithmically.

My deck has a volume indicator that runs between 0 and 34. I usually run at about 27, Assuming each notch is 3db adjustment, at 27, the signal is at max .03 volts.

If all that is correct, I am now understanding the importance of line drivers.

btw: I'm going to order a line driver tonight. Thanks for everyone's input!

Mike: I had the 21010. Like I said its a great EQ. At the Time I was running looking for a powerd (line boosting eq) it didnt work very well for that. So I bought a Earthquake PA4000 it was a powerd EQ it pushed as much as 12v. After that I bought the Audio control Line driver. And then I had a powerd EQ pushing into a line Driver (way to much voltage) so then I sold the Earthquake eq and bought the Passeve PPI Par 650 out of the 6 EQs I have owend, Including a Old school Zapco PX this is the bes ED so far

craig,

i dont know the "exact" details but there are a couple things to consider..

- preamp stage is a mini 2 stage amp (input and output)
-the higher the quality the more volts it can swing into a lower impedence (my home tubed preamp arc ls-25 put out 40 volts into 200k output impedence)

-system matching (amp input sensitivity and preamp output voltage AND impedence.

-high quality preamps stages are really rare in head units

-there isnt alot of info on this but most people that have high voltage find out it sounds better...

grant, old school ppi rules !!!! i love that stuff.. any suggestion with dual volume controls ? (one for the boat and one for the tower)

PPI Par 650
IMO it what head unit you couple the Eq with . Im running the CMD-4 with the PPI EQ and I have plenty of Line voltage

Craig,
How much attenuation there is per step on your head unit depends on the circuitry used. For example, the first 10 steps down from MAX on your HU might be 3db steps, and then 1db steps until you are at your min. So, I don't believe your logic is valid, due to the assumption you made.

Also when talking about signals, 3db down doesn't cut the amplitude in half. However, when talking about power, 3db down is half power. To use your same example

At a 2v signal strength, when you turn the volume from max down 3db, the max signal then becomes 1.41v (0.707*2V), down another 3db it becomes 1v, one more 3db 0.707v

So you can see that signal amplitude decreases by half every 6db.

Hope this helps clear things up for you.

Tom



(Message edited by wakeprodigy on August 29, 2006)

got it...And yes, things are becoming much clearer.
So Power strength doesn't equal Amplitude.

Curious, Where does 0.707 come from?

Grant - is this similar to the Earthquake powered EQ you had?

http://cgi.ebay.com/EARTHQUAKE-EQ4000PXi-4-BAND-EQUALIZER-8-VOLT-OUTPUT-NEW_W0QQitemZ270020261178QQihZ017QQcategoryZ79841Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

0.707 is equal to 1/sqrt(2). Without getting into too much detail, the amplitude of a signal in db is given by Vdb = 20*log(x) where x is the voltage of the signal. So, for 1V the db value would be 0db. 3db down from this would give you -3db. So if you substitute -3db for Vdb and solve for x you will get x = 0.707. Hence when talking on the volatage scale, 3db down for a 1V signal is 0.707*1V. For a 2V signal it would be 2V*0.707 etc... Make sense?

Tom is smart.

Tom is a prodigy.

Yup thats the one I had
BTW I have a few Audio Control peices 4 sale
Line Driver
and Epicenter

tom is very, very, smart....