# Does preamp out voltage really matter?



## blamus (Mar 9, 2009)

I'm deciding between the Pioneer AVIC F700BT (~$400) and the F90BT(~$500) The only difference are:

F90BT can play DVD, ipod cable ($50), 4v preout (as opposed to 2v)

I do have an iphone but I don't really care about the ipod cable because I'll use a USB harddisc anyway for music. I can't even imagine myself watching DVD in my car, and I only own DIVX, not DVDs anyway. 

So the ONLY difference is the 4v output as opposed to 2v.

Is that worth $100? I have been reading around and I know that higher voltage preout is a very good thing, but how much practical difference does it really make? Am I going to hear the difference? How much extra would you pay for the 4v preout? 

I'm planning to power everything with 2 class D amps - Kenwood X4R (2-way active front stage) and Planet Audio BB150.4 (bridged for 600W RMS to power 1x DIYMA R12)


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## mSaLL150 (Aug 14, 2008)

The pre-outs on my 880prs are weaksauce, I dont like pegging the gain on my amplifiers. A line driver is a possibility I am considering. IMO pre-amp voltage is pretty important.


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## freemind (Sep 11, 2008)

2v is not worth your time.


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## Hillbilly SQ (Jan 26, 2007)

The higher the better especially if your amps need lots of preout voltage to really get going. My amps won't reach full output without at least 9 volts going to them.


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## JohnnyTwoTone (Sep 7, 2008)

What I want to know is; I have a deck that has 8v outputs but my amps say they have an input sensitivity of up to 4vs. So, if I plug my 8v HU into those 4v amps does that mean that I should simply keep the gain knob all the way down, or do I still have to fool around with the gain to get it just right?

It seems like you wouldn't need to turn up the gain if there's more voltage going to the amp than the amp is sensitive to.


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## Mooble (Oct 21, 2007)

The more the better! Many HUs don't put out their stated wattage. Even when they do, it's often at full volume and with the EQ boosted to its max. Like Hillbilly, I need a lot of voltage to get my amp moving.

To the OP, no it's not worth it because you could get a better quality line driver for the same $100 that will out out more than the 4v would anyway. Get a line driver and you'll get at least 8v since most line drivers I've seen have a 4:1 gain ratio.


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## MarkZ (Dec 5, 2005)

I don't understand why everybody is so opposed to adjusting their amplifier's gain.

If the amp is INSTALLED correctly (ie. ground loops are minimized, signal cables / routing good, etc) and it doesn't suck, then low voltage input should be just fine. The gain adjustment is usually just a voltage divider feeding a buffer. It's not like it's an EQ boost or something. I don't understand the point of the line driver in this whole thing... So you guys are saying you want to BUMP UP the voltage before it hits the amp only to cut it down again as soon as it's in the amp?? Makes no sense. In the process, the line driver is just one more piece that you have to worry about ground loops and isolation..


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## ErinH (Feb 14, 2007)

I used to think it didn’t matter. But, after dealing with some noisy amplifiers, I’ve kind of changed my opinions. In short, if you want to minimize your ground noise potential, go higher. If you don’t think this is a problem with your car, then I don’t see it as a must. 

$.02


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## chad (Jun 30, 2005)

bikinpunk said:


> I used to think it didn’t matter. But, after dealing with some noisy amplifiers, I’ve kind of changed my opinions. In short, if you want to minimize your ground noise potential, go higher. If you don’t think this is a problem with your car, then I don’t see it as a must.
> 
> $.02


if you can un-plug the signal input and hte noise is still there than it's a noisy amp, if the noise is only there with something plugged into it then it's what's in front of the amp. Usually if I find an amp noisy, I also find that it's broken or older than me.


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## blamus (Mar 9, 2009)

Thx guys for your input! I was going to ask for some recommendations for line drivers, but that post got lost somewhere for some reason, and now I think I'll just go for the F90BT and call it a day.


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## THATSALEXUS? (Mar 23, 2009)

JohnnyTwoTone said:


> So does that mean that I should simply keep the gain knob all the way down, or do I still have to fool around with the gain to get it just right?



You will always need some form of gain adjustment to tune the output levels for your system, your vehicle and your listening preferences.


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## THATSALEXUS? (Mar 23, 2009)

MarkZ said:


> I don't understand why everybody is so opposed to adjusting their amplifier's gain.


(does this site not support "multi quote"?)


Amplifier gains will always need to be adjusted. Ideally, you would want to have to turn them up as little as possible. 

A higher signal voltage does alot for you. First, it keeps the noise floor to a minimum. Secondly, it has a huge inpact on dynamic range. A deck with a 2V output can accurately track the original recording between 0V and 2V. A deck with an 8V output can acurately track the original recording between 0V and 8V (less compression of dynamic range, less distortion at higher amplitudes)

In short, a higher input voltage will provide a higher sound quality advantage over turning up an amplifiers gains to achieve the same output voltages.


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## chad (Jun 30, 2005)

it has little to no impact on dynamic range, it CAN improve S/N ratio due to the attenuation of induced noise. I see no reason for the "gains way down" mentality. you are basically running witht eh most amount of attenuation possible thus making the chance for level mis-match due to potentiometer tolerances much greater


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## dbiegel (Oct 15, 2006)

I can't speak as to how useful the extra preamp voltage is on the F90BT... BUT when making the same decision you are faced with, one thing I considered was the possibility that the preout voltage isn't the only technical difference (although it's the only one Pioneer marketing publishes). Like other Premier units, the F90BT might have better SQ than the non-Premiers due to better components or design.

On the other hand, it might be exactly the same other than the preout voltage. Unless someone has compared the two circuit boards, it's anyone's guess. For me, this was a factor in my deciding to spend a little more for the F90BT version.


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## 14642 (May 19, 2008)

Preout voltage does make some difference. There's a mucg bigger difference between 100mV and 2V than there is between 2V and 4v. The difference between 100mV and 2v is about 26dB and the difference between 2 and 4V is 6dB/ The idea is that the signal should be much louder than the noise. 

Why not use the speaker level outputs? They'll be about 5V and completely isolated from ground.


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## kyheng (Jan 31, 2007)

Well, I only know the following :
Lots of amps pre-in is around 0.2-4V
2V pre-out HU is just ok to begin with sometimes noise issues
4V pre-out HU is just nice for average usage 
>4V is bonus
>6V is overkill if using lower pre-in range amps
At the end of day, choosing amps is like choosing HU, you have to get the best match between 2 of them.


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## blamus (Mar 9, 2009)

Andy Wehmeyer said:


> Why not use the speaker level outputs? They'll be about 5V and completely isolated from ground.


I imagine double amping signal like that can introduce distortion and lower quality etc?


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## chad (Jun 30, 2005)

Andy Wehmeyer said:


> Preout voltage does make some difference. There's a mucg bigger difference between 100mV and 2V than there is between 2V and 4v. The difference between 100mV and 2v is about 26dB and the difference between 2 and 4V is 6dB/ The idea is that the signal should be much louder than the noise.
> 
> Why not use the speaker level outputs? They'll be about 5V and completely isolated from ground.


A man after my heart 

And thank you for mentioning the amount of gain these differences are. I'm a firm believer standardization to Decibels of nominal operating output level should be adopted and the voltage ratings should be thrown out the window. Life would be MUCH easier.



blamus said:


> I imagine double amping signal like that can introduce distortion and lower quality etc?


Well, this distortion CAN turn up when driving a speaker BUT the amplifier has a high impedance input MUCH, MUCH Much higher than the 4 ohms of a a speaker. In this arena many integrated output IC's act just like what they are, Op-Amps with really high current rails that are really stable. Many headunits are not only isolated in ground but internally bridged, meaning you now have differential outputs, uber low output impedance, and comparatively massive current capability. if utilized properly and you are indeed concerned about "output voltage" then the benefits of these outputs would greatly out-weigh the issues of "double ampling" which in theory you are not, there's a buffer op-amp on your preamp outs too


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## Hillbilly SQ (Jan 26, 2007)

I'm going to go ahead and say my pg tld66 is THE BEST $60 I've ever spent on my system. Dynamics went through the roof and hiss is nonexistent. Too many people also forget how important independent channel attentuation is. I don't know how many times I've gotten into someones vehicle and had the left tweeter make my left ear bleed while wondering if the right tweeter is even hooked up.


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## buchaja (Nov 10, 2007)

So could I use the 4v outputs of my drz to drive a tweeter? No need for an amp?


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## benny (Apr 7, 2008)

something made to push 10Kohm might not like driving 4 or 8 ohm. My guess.


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## MarkZ (Dec 5, 2005)

The entire discussion makes the assumption that the dominant source of electrical noise (in the car) is noise induced into the signal cables. When has that ever been demonstrated? I can't think of very many real world scenarios where that's true, actually.

Noise generally comes from... 
*ground loops 
*ugly power source fluctuations (exacerbated by dying batteries and eroding connections...) 
*bad grounds in general (how many people here upgrade their head unit ground anyway?)
*crappy board layout in the amplifier 
*power supply switchers, etc. 

Higher preout voltages aren't really going to tackle those things. So where does induced noise betw. HU and amplifier rank among those? I'd say pretty low in most cases. My two cents..


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## buchaja (Nov 10, 2007)

benny said:


> something made to push 10Kohm might not like driving 4 or 8 ohm. My guess.


Hmm... 0.4mA vs. 1 Amp. 

I always wanted to use my nice, new Clarion to make toast on road trips. :laugh:


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## chad (Jun 30, 2005)

buchaja said:


> So could I use the 4v outputs of my drz to drive a tweeter? No need for an amp?


No, Look at a schematic, there is an output buffer resistor on the op-amp to protect it from shorts and is driven from a low current supply. An output IC is a glorified op-amp, an op-amp is not a glorified power IC.

HOWEVER an op-amp WILL drive a speaker, proof in point is the Smopky line of tiny guitar amplifiers.


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## suds1228 (Apr 22, 2008)

My Soundstream Van Goughs have a switch that allows me to toggle between 4V or less or >5V input. However when I do use the high voltage side the music seems less dynamic and "pushed".


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## chad (Jun 30, 2005)

suds1228 said:


> My Soundstream Van Goughs have a switch that allows me to toggle between 4V or less or >5V input. However when I do use the high voltage side the music seems less dynamic and "pushed".


You are runnign the headunit on the ragged edge 



Andy Wehmeyer said:


> There's a mucg bigger difference between 100mV and 2V than there is between 2V and 4v. The difference between 100mV and 2v is about 26dB and the difference between 2 and 4V is 6dB/ The idea is that the signal should be much louder than the noise.


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## suds1228 (Apr 22, 2008)

chad said:


> You are runnign the headunit on the ragged edge


So Less HU volume and more preamp.


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## chad (Jun 30, 2005)

some headunits don't' like to be run flat out, some don't mind it at all.


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## AWC (Mar 31, 2008)

*****comic interlude*******


I have a planet audio line driver hooked up to each nipple Y'd off of the sub...you bet your ass the voltage matters and when bitches gots GIN AND JUICE!!! WHOOOO!!!!


*****please continue...whatever it is you guys were talking about.


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## eRush (Apr 2, 2009)

Hillbilly SQ said:


> My amps won't reach full output without at least 9 volts going to them.


I am not saying that you are wrong, but I havent heard this before. What amp are you running???


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## chad (Jun 30, 2005)

eRush said:


> I am not saying that you are wrong, but I havent heard this before. What amp are you running???


If I ever meet him I'm gonna prove him wrong


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## Mooble (Oct 21, 2007)

eRush said:


> I am not saying that you are wrong, but I havent heard this before. What amp are you running???


I have the same problem. My Tru was factory modified to accept 4v minimum input. With anything less, I cannot get full power from the amp. This lowers the noise floor substantially, but it requires a line driver. My 880PRS supposedly puts out 5v, but we all know manufacturers have a way of fudging the numbers. I can promise you that a line driver is absolutely necessary in my case, but probably isn't to most people.


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## chad (Jun 30, 2005)

Mooble said:


> I have the same problem. My Tru was factory modified to accept 4v minimum input.


useless, utterly useless.

To think amps people make money with with make power at .775V, 1.4V, or 26dB of voltage gain.

Another reason for standardization... big time.


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## blamus (Mar 9, 2009)

hmmm. So when I get my new HU, how would I know if I would benefit/need a line driver?


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## eRush (Apr 2, 2009)

blamus said:


> hmmm. So when I get my new HU, how would I know if I would benefit/need a line driver?


By scoping the output at max volume and seeing if it shows any clipping.


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## chad (Jun 30, 2005)

eRush said:


> By scoping the output at max volume and seeing if it shows any clipping.


lets try hooking it up, setting the gains by ear and forgetting about it, if your install is up to par you will be just fine.


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## t3sn4f2 (Jan 3, 2007)

blamus said:


> hmmm. So when I get my new HU, how would I know if I would benefit/need a line driver?


If you run out of clean gain from any of the devices in the chain.


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## eRush (Apr 2, 2009)

chad said:


> lets try hooking it up, setting the gains by ear and forgetting about it, if your install is up to par you will be just fine.


My experience has shown that the average person/listen wouldnt be able to do that.


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## t3sn4f2 (Jan 3, 2007)

eRush said:


> My experience has shown that the average person/listen wouldnt be able to do that.


But they can appreciate the detail accuracy of a scoped signal?


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