# Benefits of high voltage pre-amp outputs.



## Fricasseekid (Apr 19, 2011)

I just installed an Eclipse dead head unit that has 8v RCA outputs. Is there any benefit in having the higher voltage preamp outputs other than the ability to set your gains lower? 

There is alot I dont understand about this, such as:
If the difference in amp wattage between 12v and 14.4 volts is so great, why doesn't doubling your preamp voltage allow you to make more power?

What's the difference, SQwise, between setting gains low and running the HU at full throttle (assume no clipping), as opposed to running a HU at half volume and setting gains higher to compensate?

Is reduction in noise floor the only benefit of high voltage preouts?


One more thing; Should this be in the dumb questions section, cause I don't see alot of discussion about it?


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## kyheng (Jan 31, 2007)

Higher pre-amp voltage are for noise rejection, nothing more than that.... Balanced pre-outs/ins are mainly for long lenght from 1 point to another(like a concert hall), just that some companies uses this for marketing gimmick....
Amp's pre-in and output power are depending the multiplier(gain), so if say the amp accept max of 4V pre-in, at that voltage, the amp should have the rated output. With your HU, the gain should be in 0.2V to get an uniform volume control.... But my explanations could be wrong on this....
As for the 12V or 14.4V, I will see the power at 12V only, as that is more accurate. Some car can do 14.4V, but my car can't. Under car enviroment, what more important will be the external noise, I'll put more effort on this.....


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## Fricasseekid (Apr 19, 2011)

Ok well, one more question,

If you can set your gains lower because of a stronger preamp signal, does that mean your amp will run cooler?


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## chefhow (Apr 29, 2007)

Eclipse HU's don't reach 8v output until 69-70/72 on the volume.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

The amp wont run any cooler, because if you set the gains properly, you'll still be putting out the same power, just with lower gain and less noise.


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## mires (Mar 5, 2011)

Fricasseekid said:


> One more thing; Should this be in the dumb questions section, cause I don't see alot of discussion about it?


Nah, this is the right place for it I think. I would definitely like more information on the subject as well as I have the 8443. Are you running the 8053?


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## tonesmith (Sep 8, 2011)

Running the gains lower will result in a lower noise level at any given volume. How much of a difference it makes, beats me.


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## denetnz (Jul 31, 2009)

tonesmith said:


> Running the gains lower will result in a lower noise level at any given volume. How much of a difference it makes, beats me.


Road noise could easily be 70db, so unless you have the world's first completely silent car, my guess is absolutely no difference when the car is moving - or even running for that matter...


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## Jani X (Sep 10, 2009)

It has been said by some competitors (whos views I deeply respect) that *some amps* sound better when you adjust gains higher than usual "proper" way would be. I have been thinking what the heck could be the reason for that... ?? 
Something to do with structure or class of amps pre-stage ...?


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## kyheng (Jan 31, 2007)

As far as possible, I'll prefer to crank my HU's volume control as high as I can, Pioneer I can go till max.....


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## fisc2307 (Oct 29, 2011)

Your gain is to match the head unit preamp voltage to the amplifiers voltage. 12V is what your battery runs at (aka the voltage your car has when its sitting in the driveway). 14.4V is the Voltage your car should be outputting if the engine/alternator is running. If your car is not running at 14.4 V you may have a problem with the voltage convertor or the alternator itself in your vehicle. Again as other people are saying, especially if you have a car that is older and as the car gets older, panels and materials wear out and more and more NVH (noise, vibration, harshness) is transmitted into the cabin. Unless you're driving a newer luxury vehicle ($40,000+) you wont notice the THD imputed into the system.


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## Sean Morrison (May 27, 2007)

Many older amps didn't even accept higher than input voltages. Like the PPI arts for example only go up to 2.5V input.


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## Fricasseekid (Apr 19, 2011)

mires said:


> Nah, this is the right place for it I think. I would definitely like more information on the subject as well as I have the 8443. Are you running the 8053?


I'm running the 8052.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

fisc2307 said:


> Your gain is to match the head unit preamp voltage to the amplifiers voltage. 12V is what your battery runs at (aka the voltage your car has when its sitting in the driveway). 14.4V is the Voltage your car should be outputting if the engine/alternator is running. If your car is not running at 14.4 V you may have a problem with the voltage convertor or the alternator itself in your vehicle. Again as other people are saying, especially if you have a car that is older and as the car gets older, panels and materials wear out and more and more NVH (noise, vibration, harshness) is transmitted into the cabin. Unless you're driving a newer luxury vehicle ($40,000+) you wont notice the THD imputed into the system.


I agree on the noise, but there are a ton of cars that don't put out 14.4 volts. My wifes brand new civic puts out 13.8. My dads brand new Tacoma puts out 14. 14.4 is ideal, bit not having it doesn't really mean somethings wrong.


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## chad (Jun 30, 2005)

Here's the deal, you will ALWAYS have noise induced on the line going to the amplifier/preamp/whatever.

So if you have X amount of signal going to the amplifier you are setting the gain structure up for Y amount of voltage gain at the amplifier, this voltage gain amplifies both the intended signal and the noise.

If you increase the output of the source to 4X then you decrease the voltage gain at the receiving end /4 this leaves you with the same amount of voltage at the output for the intended signal but induced noise is reduced by a factor of 4.


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## Ianarian (Dec 20, 2010)

Fricasseekid said:


> I just installed an Eclipse dead head unit that has 8v RCA outputs. Is there any benefit in having the higher voltage preamp outputs other than the ability to set your gains lower?
> 
> There is alot I dont understand about this, such as:
> If the difference in amp wattage between 12v and 14.4 volts is so great, why doesn't doubling your preamp voltage allow you to make more power?
> ...


Your preamp voltage has nothing to do with the output power. Fluctuating the input voltage to the amp, only changes the magnitude in which the amp receives signal. The amp is just a regulated quantification of whats received.


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## Fricasseekid (Apr 19, 2011)

Thank you everyone for the responses. 

One more question. This might seem dumb though...

What does the amplifier do with the extra voltage? I dont really understaffed many EE concepts, but it seems to me that what goes in must come out. So how can you double the input signal voltage and nothing changes in the amp aside from the gain position?


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## kyheng (Jan 31, 2007)

Case by case... If you are using regulated amps, then power at 12 or 14.4V does not matter.... If unregulated then you will have some difference on the power output... Again, cabin gain and external noise will be your public enemy....


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## Hillbilly SQ (Jan 26, 2007)

The extra voltage comes out in the form of clipping/distortion if the gains are set too high. Remember, the gain on an amp is just an attentuator.


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## AAAAAAA (Oct 5, 2007)

If the amp can only accept up to, let say 4 volts input and the deck can actually put out 8... usually amps don't have a problem accepting higher voltage... from what I understand they would simply take the 8volt but use it as if it were 4.... essentially the end results is just lke compressing music, making everything the same loudness.


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## t3sn4f2 (Jan 3, 2007)

IE extra voltage is like you growing from 6 ft to 9ft and trying to stand up tall in a room with an 8 ft ceiling. You'll be ok from the neck down but your head will be all f'ed up.


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## Fricasseekid (Apr 19, 2011)

t3sn4f2 said:


> IE extra voltage is like you growing from 6 ft to 9ft and trying to stand up tall in a room with an 8 ft ceiling. You'll be ok from the neck down but your head will be all f'ed up.


This is why I don't wear underwear.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

Another thing, i doubt it actually does 8 volts. I remember a thread on another forum where a Denon was measured, and it put out 6.7 volts or something like that with a 0db tone. That was also a 8volt unit.


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## keefebrennan (Jan 23, 2013)

Jani X said:


> It has been said by some competitors (whos views I deeply respect) that *some amps* sound better when you adjust gains higher than usual "proper" way would be. I have been thinking what the heck could be the reason for that... ??
> Something to do with structure or class of amps pre-stage ...?


This is a very interesting observation. It was discovered back in the 30's that human hearing has a frequency response that alters with the intensity of a sound. Both bass and treble are attenuated at low levels, bass more so than treble. Its believed that we evolved this way to be more alert to higher frequencies making us better hunters (we could hear the sound of rustling leaves and snapping twigs easier). This helps explain why people believe that subs sound better loud, because they do, it just has nothing to do with the speakers or amp quality.
Honestly cheaper class A amps could possibly sound better at higher gains since they are very inefficient and produce lots of heat because there is a large amount of current flowing through the output transistors even with no audio signal so lots of voltage goes to waste.
I Think the former is the main reason. Its just an audible illusion.


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## chad (Jun 30, 2005)

I believe that they are speaking of for X output the amp is apparently sounding better with the gains up and the source output lower.

I sort of attribute this to the fact that the vast majority of gain pots are ganged dual channel and they simply track each other more accurately when they are not operating at the lower extreme of their throw.


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## Fricasseekid (Apr 19, 2011)

chad said:


> I believe that they are speaking of for X output the amp is apparently sounding better with the gains up and the source output lower.
> 
> I sort of attribute this to the fact that the vast majority of gain pots are ganged dual channel and they simply track each other more accurately when they are not operating at the lower extreme of their throw.


I have no idea what your talking about.


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## chad (Jun 30, 2005)

Go to your home stereo, plug in headphones, start turning the volume down, one channel will stop playing before the other.

Dual gang pots don't track each other for **** at (especially) the lower end of the throw.


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## Fricasseekid (Apr 19, 2011)

I see.


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