# Why do 2V RCA outputs even exist, still?



## sirbOOm (Jan 24, 2013)

Dear car audio brands:

If a HU has 6-channels of pre-amp outputs, the design assumption should be that the buyer will indeed add amplification in their car. There is no f'ing reason to have 2V pre-amp outputs on such models. Should be 4V+ only.

In fact... it's 2013 now. Drop the 2V pre-amps altogether! :mean:

2V bad 
:stupid: 4V+ good oke:

...rant over


----------



## jowens500 (Sep 5, 2008)

There are less than a handful of radios made today that even have a TRUE PRE amp section.


----------



## sirbOOm (Jan 24, 2013)

Gotta be caused by global warming... and Obama. :bulb2:


----------



## cyrusthevirus23 (Feb 16, 2013)

im shocked they still exist what a waste of funds


----------



## shawnk (Jan 11, 2010)

sirbOOm said:


> Dear car audio brands:
> 
> If a HU has 6-channels of pre-amp outputs, the design assumption should be that the buyer will indeed add amplification in their car. There is no f'ing reason to have 2V pre-amp outputs on such models. Should be 4V+ only.
> 
> ...


The extremely low noise floor of todays amplifiers makes me wonder why you "think" you need any more than a 2v preamp :shrug:


----------



## sirbOOm (Jan 24, 2013)

For the same reasons people put spoilers on FWD econo cars... it adds power, bro!

(I know it doesn't add power...)

















(or does it............ :rockon::shocked::elvis


----------



## cyrusthevirus23 (Feb 16, 2013)

i always had better outputs with the 4volts over the 2


----------



## shawnk (Jan 11, 2010)

"Most" car audio amplifiers will reach their clipping threshhold with a mere 1v (or even less) input when the gain is adjusted to its maximum setting.

The only advantage that a "4 volt" output will give you over a "2 volt" output is the ability to minimize the gain of the amp thereby reducing noise floor. But as I had previously stated, modern amplifiers have very low noise floor even with maximum gain settings.

I would have to believe that you are driving your amplifiers well into clipping if you think 4 volts is an improvement over 2 volts. I see no legitimate reason why anyone could not build a complete car audio system using a 2v preamp and not have optimum performance.

This discussion of coarse is leaving out the hardcore spl competitors where hard clipping is par for the coarse


----------



## sirbOOm (Jan 24, 2013)

I get the point trying to be made (and agree with it). You can indeed have a 2-volt pre-out head unit, an amplified system, and hear no noise. It's possible, it's likely, it's common (especially when gains are set properly and your amp is recent).

The 2v vs. 4v debate is akin to debating whether or not JL Audio products are overpriced for what they are. I'd say the price is unnecessarily high in many instances just as in most circumstances 4-volt pre-amp outputs aren't truly necessary (for the purpose of reducing audible noise). Nevertheless, in both instances, with your purchase you know you're getting something that, overall, is going to deliver well in your particular vehicle, assuming you haven't made some overt installation error or have malfunctioning kit.

We all don't have the same vehicle. We all don't have the same amplification. We all don't have the same skills in setting gains and keeping audio wires away form or perpendicular to power wires, where possible. Nevertheless, all of us should not be hearing alternator whine or other noise that 4-volts could have reduced or prevented (understanding still that a problem does exist below the covers, in that situation). 

It's 2013 now. Unless having a 2-volt pre-amp output actually REDUCES noise sourced from WITHIN the head unit somehow, then there's no reason for 2-volt to still exist. Especially with cars that have powered center consoles, seats, and other bits that have often pretty thick power wires running on both sides and the middle of the car.

When Pioneer sells a new Stage 4 head unit with 2-volt pre-amp outputs, I'll believe that 4-volt+ doesn't have the worth that I attribute to it. Then again, the latest McIntosh has 3-volts... but it's a McIntosh (and 3 is still higher than 2).


----------



## shawnk (Jan 11, 2010)

Just trying to help here so please don't take my comments the wrong way cool..?



It appears that you are confusing "noise floor" with "induced noise" which are two different animals. It also appears that you are under the assumption that a 4v output can somehow reduce (or block out?) induced noise bette than a 2v output. This is false. If this were true, then even the "4v" capable preamp would have induced noise issues when the volume is low. Remember, the signal is not a constant 4v (or 2v). When listening to a system at low volume, for instance, the signal feeding the amplifiers could feasibly be only fractions of a volt. So....

Also keep in mind that there are indeed plenty of amplifiers (even new amplifiers) that will NOT even accept a 4 volt signal input without going into clipping!


----------



## cruzinbill (Jul 15, 2011)

I agree with what some others have said. I dont really think its something that is a huge deal these days. While I think it gives more room for things I think decks, amps, and processors these days are just built better and dont "need" it.

Now.... to not skew to far from the thread.... I do believe rca should be phased out and digital (such as toslink or alpines ainet) should be standard. Leave the D/A conversion in the amp side of the house.


----------



## sirbOOm (Jan 24, 2013)

Nope, I don't take learning things the wrong way. I am indeed mixing types/sources of noise. I do not claim to be an expert -- that's why I joined this form... to get better. But I have my perspective and experiences, which are nonetheless valid. And all of them have resulted in a 4-volt output contributing to a better overall audio system.

Why not just make all of them 2-volt... if it doesn't matter?
Why does Pioneer equip their Stage 4 with 5-volt pre-outs?
Why do high end audio processors feature 4+ volt outs?

Understanding that this voltage is dependent on certain variables and certainly not constant, I'd like to keep the gains on my amplifier(s) as low as possible. Not necessarily because, these days, I need to be worried about noise caused by my audio components, but because if 4-volt is going to offer me any benefit, I want it.

Back in high school, I went from a Pioneer 2-volt model to the next model up which had 4-volts. No other real difference. Gains were adjusted properly in both instances. Zero noise in the 4-volt (no alternator whine, no hiss, no nothing). These were MTX amps back when MTX amps were underrated and awesome. Friend went from a 4-volt model to a 2-volt model and no matter what we did, it never got as loud. He had Clarion amps.

We were like the noob-iest of noob then. And we knew it. (We were so noob we even changed our reverse lights from normal white to blue! Added like 15 hp!!!) But in both instances, our parents made us take the car to the local audio shop (not Best Buy) to get set up properly after we installed everything based upon what we learned from sounddomain.com (when it existed) because we didn't know what the knobs did on the amplifiers. Same amps - up to 4 volt got better, down to 2 volt got worse.

Rinse and repeat in every example I've seen since.

Amplifiers have gotten way better. Class D tech. is now usable for highs! But maybe it's like buying an extended warranty... I want the assurance I'm getting something that is going to deliver. 2-volts doesn't offer up that assurance (to me). It doesn't to a lot of people, even seasoned vets. I've been to competitions (not SPL-focused) where I asked about 2v vs. 4v and they all said 4v is what they'd prefer (and have, or higher). I didn't ask also, "Could you get away with 2v?" The answer would have been no by default - because the units that come with 2v tend to be lower end and they want high-end.

Thanks for the comments... this is good learning for me.


----------



## sirbOOm (Jan 24, 2013)

cruzinbill said:


> Now.... to not skew to far from the thread.... I do believe rca should be phased out and digital (such as toslink or alpines ainet) should be standard. Leave the D/A conversion in the amp side of the house.


Is an HDMI (or HDMI-style) cable such a solution? I am surprised RCA cables are still used in car audio given there's been so much digital advancement in home audio/video. That'd be really cool to just plug in one HDMI cable and be done.


----------



## cruzinbill (Jul 15, 2011)

sirbOOm said:


> Nope, I don't take learning things the wrong way. I am indeed mixing types/sources of noise. I do not claim to be an expert -- that's why I joined this form... to get better. But I have my perspective and experiences, which are nonetheless valid. And all of them have resulted in a 4-volt output contributing to a better overall audio system.
> 
> Why not just make all of them 2-volt... if it doesn't matter?
> Why does Pioneer equip their Stage 4 with 5-volt pre-outs?
> ...


If you're paying for high-end premium gear they are gonna include any and everything.

I'm not saying 4v isn't better than 2v. Just that its not really necessary with today's equipment. But that's my opinion everybody has there own... that's why all these different outputs even exist different peoples opinions of what is needed.

All I'm saying at the end of the day you can get plenty loud clean music from 2vs rcas. if that's all that mattered is the voltage why arent we running 12v preouts or something silly like that.


----------



## sirbOOm (Jan 24, 2013)

I say we petition Pioneer for 120 volt pre-outs powered by little wind turbines mounted on the side-view mirrors on cars. Then we can get some tax breaks on our audio systems.

...I'm just sayin'


----------



## chad (Jun 30, 2005)

cruzinbill said:


> Now.... to not skew to far from the thread.... I do believe rca should be phased out and digital (such as toslink or alpines ainet) should be standard. Leave the D/A conversion in the amp side of the house.


Audinate


----------



## shawnk (Jan 11, 2010)

sirbOOm said:


> Why not just make all of them 2-volt... if it doesn't matter?


Easy... Much like so many other car audio myths, we can thank the wonderful marketing departments for the "hype" 



sirbOOm said:


> Why does Pioneer equip their Stage 4 with 5-volt pre-outs?


Same deal. Marketing. It's all in the "perspective" of what potential consumers "think" is best.

Let me ask you this... just because the Pioneer Stage 4 system utilizes a 5v preout, does that mean it's a better pre amp than say the 4v Alpine F#1? No, of coarse not

Unfortunately in order for the "high-end" gear to actually sell, it almost needs to have *at least* a 4v pre out simply for the wow factor and not so much about overall performance  This here thread is a prime example. 



sirbOOm said:


> Why do high end audio processors feature 4+ volt outs?


Back in the early 90's, "high" voltage pre outs were in the 2v range. Now keep in mind that many of the source units out in that era had very low output voltage (as low as 0.25v in some cases). This meant that the input gains for many of these older amps were at their maximum setting and often times the system suffered from audible noise coming from the amp (noise floor). 

So the "high" voltage 2v outputs pretty much solved any noise issues and realistically, nothing really neaded to be changed. Then in the mid 90's, or so, the good old marketing team evidently needed a new tool to try and outsell the next guy.... in comes the venerable 4volt preout head unit... even though it was never really necessary 

So this is pretty much the era that made the "4v" output the *reference* I guess you could say.... again, even though it wasn't necessary

In the end, there's nothing magical about a 4v output, especially when comparing to say 2v, within the car audio realm. I have built dozens upon dozens of wonderfully sounding and perfectly quiet (refering to distorion, noise floor, and induced noise) systems using sources with outputs that provide 2 volts (or even less).

Hell, I would gladly take a measly 1v balanced line signal over a ground referenced phono cable any day


----------



## SaturnSL1 (Jun 27, 2011)

It don't even matter playa.


----------



## chad (Jun 30, 2005)

shawnk said:


> Hell, I would gladly take a measly 1v balanced line signal over a ground referenced phono cable any day


On mini XLR plz, rated in decibels in reference to 0dBu. All problems solved.

Also folks need to keep in mind that HOME AUDIO IS -10 dBV which is .316V nominal, FWIW most pro audio is +4dBu which is 1.228V nominal but will hit +18-22dBu easily.

Also keep in mind that at concerts you see mics on the stage, these have an output of -35dBu that is 0.013V That travels 20-50 feet across an electrically noisy stage, to a transformer split where it is split a minimum of 2 times, generally 3, then travels down 150 feet of multicore snake to FOH where an assload of gain is applied, then sent back to the stage at 1.2V nominal where another assload of gain is applied in the form of power amplification.

Been doing this for a LONG time, longer than car subwoofers, nobody has died from not having a 4V+ microphone.


----------



## Pitmaster (Feb 16, 2010)

Does the signal impedance of the preamp out matter?


----------



## sirbOOm (Jan 24, 2013)

At least it wasn't an HR department that came up with it... then you'd be required to believe that 4 volt was necessary as a condition of use. It'd say it right there in the policy.


----------



## cruzinbill (Jul 15, 2011)

chad said:


> Audinate



Exactly!! whats the hold up?



chad said:


> On mini XLR plz, rated in decibels in reference to 0dBu. All problems solved.
> 
> Also folks need to keep in mind that HOME AUDIO IS -10 dBV which is .316V nominal, FWIW most pro audio is +4dBu which is 1.228V nominal but will hit +18-22dBu easily.
> 
> ...



Are you 100% sure that no one has died? Have you taken a poll and do you have proof of said poll?


----------



## sirbOOm (Jan 24, 2013)

A lot of "singers" these days lip sync... maybe it's cuz they only have 2 volts?


----------



## cyrusthevirus23 (Feb 16, 2013)

sirbOOm said:


> I say we petition Pioneer for 120 volt pre-outs powered by little wind turbines mounted on the side-view mirrors on cars. Then we can get some tax breaks on our audio systems.
> 
> ...I'm just sayin'



lol that would be something else, like seeing pigs fly


----------



## sirbOOm (Jan 24, 2013)

I seen a pig fly. In the form of bacon. Into my mouth at Denny's.

GRAND SLAAAAAAMMMMMM! Get some.


----------



## shawnk (Jan 11, 2010)

Pitmaster said:


> Does the signal impedance of the preamp out matter?


It's debatable.

Without trying to get into it too awefully much, a lower output impedance is always better than outputs with high impedance.

Basically, there is always a resistance to current in cables. To be more specific, with AC volatge (our music signals) this is impedance, and impedance will rise as the cable gets longer. This causes attenuations in the high frequency. So the short answer is, high impedance attenuates high frequency.

I have an older RF deck that boasts an ultra low 50ohm output impedance and it's a great sounding deck, but also keep in mind that I've done numerous systems with Alpine headunits that have 10k ohm output impedance and I've never noticed any loss in high frequency reproduction.  I think you would need to approach the 50k ohm range to actually detect a noticeable difference.


----------



## Maylar (Dec 6, 2012)

shawnk said:


> It's debatable.
> 
> Without trying to get into it too awefully much, a lower output impedance is always better than outputs with high impedance.
> 
> ...


Fixed. And I'll take issue with a couple of points here. I think you're off by an order of magnitude (I'd believe 1K source but not 10K ohms in a preout). Are you sure about that?

Secondly, I once did a calculation on the losses in an RCA cable due to the capacitive loading - this was for a magnetic cartridge in a turntable (47K ohm source) and a high end 6 ft cable had enough capacitance to shunt 10 Khz to 50%. A 15 ft RCA with 50K source would leave nothing for highs.

But the real advantage of low source impedance is in noise immunity. The lower the impedance the less radiated noise can be picked up. Which is why I'm an advocate of using high level speaker lines for amp inputs.


----------



## shawnk (Jan 11, 2010)

Maylar said:


> Fixed. And I'll take issue with a couple of points here. I think you're off by an order of magnitude (I'd believe 1K source but not 10K ohms in a preout). Are you sure about that?.


Wait what?? I'm sorry but you'll have to expain much further if you're going to "fix" my statements. I'm under the impression that you believe that impedance actually drops as a signal cable is increased. I will certainly not claim to be an EE by any means , but this contradicts everything I have learned over the years. EVERY cable has at least "some" resistance which translates to impedance when dealing with AC, and the longer a cable is, the more resistance/impedance can be measured. Again, I'm no EE, but this is fundamental stuff :worried:

And yes I'm sure about many Alpine head units having *10k ohm* source impedance 




Maylar said:


> Secondly, I once did a calculation on the losses in an RCA cable due to the capacitive loading - this was for a magnetic cartridge in a turntable (47K ohm source) and a high end 6 ft cable had enough capacitance to shunt 10 Khz to 50%. A 15 ft RCA with 50K source would leave nothing for highs..




Now this statement (although doesn't really pertain to car audio...47k is quite high!) more or less reinforces what I've already stated.... that high impedance can reduce high frequency response (I was trying to keep in simple )



Maylar said:


> But the real advantage of low source impedance is in noise immunity. The lower the impedance the less radiated noise can be picked up. Which is why I'm an advocate of using high level speaker lines for amp inputs.


I'm not going to say you are wrong here as I have not done any testing on this myself, but I'm not so sure here. I'd really like to see some proof of this. I'm quite confident that radiated noise can be induced into a signal cable regardless of impedance OR voltage capabilities.


----------



## Pitmaster (Feb 16, 2010)

The reason I ask is that my Eclipse HU is rated at 55 ohms, but for most consumer units, 10k ohms seems to be very common.


----------



## chad (Jun 30, 2005)

Lower is better.... 600 ohms was the defacto in pro audio and telcom forever.... Back when things had to be matched.. Many still gravitate around 600 ohm.


----------



## Maylar (Dec 6, 2012)

shawnk said:


> Wait what?? I'm sorry but you'll have to expain much further if you're going to "fix" my statements. I'm under the impression that you believe that impedance actually drops as a signal cable is increased.


You were correct in that the high frequencies suffer when source impedance is high. The reason for this is that the distributed capacitance in an RCA cable acts as a "shunt" that bypasses the highs. The longer the cable, the more capacitance so the effective impedance (at high frequencies) goes down. Maybe this diagram will help:













> I will certainly not claim to be an EE by any means , but this contradicts everything I have learned over the years. EVERY cable has at least "some" resistance which translates to impedance when dealing with AC, and the longer a cable is, the more resistance/impedance can be measured. Again, I'm no EE, but this is fundamental stuff :worried:


The DC resistance of the wire of course increases with length. But that's fractions of an ohm and affects all frequencies equally. The loss of high freqs is due to the cable capacitance making the cable more of a load (lower impedance) on the preout source impedance.



> And yes I'm sure about many Alpine head units having *10k ohm* source impedance


Wow. That makes no sense to me. The input impedance of most amps is 10-20K ohms. That would mean the preout voltage would be cut in half when the RCAs are plugged in. Even my 10 yr old Pioneer deck has 300 ohms.




> Now this statement (although doesn't really pertain to car audio...47k is quite high!) more or less reinforces what I've already stated.... that high impedance can reduce high frequency response (I was trying to keep in simple )


Except that your assumption that the cable impedance goes up doesn't really explain the relationship to high source impedance. Hope I cleared that up for you.



> I'm not going to say you are wrong here as I have not done any testing on this myself, but I'm not so sure here. I'd really like to see some proof of this. I'm quite confident that radiated noise can be induced into a signal cable regardless of impedance OR voltage capabilities.


A high impedance circuit can/will pick up more noise than a low impedance circuit. You'll have to trust me on that. It's why we don't shield speaker wires, the impedance is so low there's virtually no chance of picking up noise.


----------



## shawnk (Jan 11, 2010)

Thanks!

Ok so apparently I need to freshen up a little on this subject. 

I understand cable capacitance and how it creates a low-pass filter in conjunction with the source impedance, but I was under the impression that it really didn't have much effect until much higher frequency than within the audible spectrum. :blush:

So if I'm getting this right then, cable impedance is still present (I don't see how it couldn't be), but it is essentially "dominated?" by capacitive reactance?


----------



## cyrusthevirus23 (Feb 16, 2013)

chad said:


> Lower is better.... 600 ohms was the defacto in pro audio and telcom forever.... Back when things had to be matched.. Many still gravitate around 600 ohm.


i learned something new today


----------



## cyrusthevirus23 (Feb 16, 2013)

shawnk said:


> Thanks!
> 
> Ok so apparently I need to freshen up a little on this subject.
> 
> ...


same here


----------



## Maylar (Dec 6, 2012)

shawnk said:


> Thanks!
> 
> Ok so apparently I need to freshen up a little on this subject.
> 
> I understand cable capacitance and how it creates a low-pass filter in conjunction with the source impedance, but I was under the impression that it really didn't have much effect until much higher frequency than within the audible spectrum. :blush:


That's correct. However...



> So if I'm getting this right then, cable impedance is still present (I don't see how it couldn't be), but it is essentially "dominated?" by capacitive reactance?


The resistive component of cable impedance (the wire itself) is insignificant when compared to the source impedance (preout) and the load (amp input impedance). The amount of "dominance" of the capacitance depends entirely on the source impedance, which is why I'm absolutely certain that no HU manufacturer would design a preout with a 10K ohm source. It would be absurd. Noise susceptability would be terrible and even the best RCA cables would have too much capacitance.

I looked at a spec sheet for an Alpine HU and it said, "Maximum Pre-Output Voltage 2 V/10 k ohms" - that's the specified LOAD impedance, not the source. It means the preouts can supply 2V into a 10K load. The source impedance would be a separate spec.

In the old days RCA cables also had specs, including capacitance per foot. I can't remember the typical numbers... the brain gets fuzzy lookin' back 35 years...


----------



## sirbOOm (Jan 24, 2013)

shawnk said:


> "dominated?" by capacitive reactance?


I think I just got turned on a little... :whip:


----------



## chad (Jun 30, 2005)

A quality cable (bulk) will always have the capacitance spec. But with the stupidfying of America they try not to confuse people these days.


----------



## MarkZ (Dec 5, 2005)

sirbOOm said:


> I get the point trying to be made (and agree with it). You can indeed have a 2-volt pre-out head unit, an amplified system, and hear no noise. It's possible, it's likely, it's common (especially when gains are set properly and your amp is recent).
> 
> The 2v vs. 4v debate is akin to debating whether or not JL Audio products are overpriced for what they are. I'd say the price is unnecessarily high in many instances just as in most circumstances 4-volt pre-amp outputs aren't truly necessary (for the purpose of reducing audible noise). Nevertheless, in both instances, with your purchase you know you're getting something that, overall, is going to deliver well in your particular vehicle, assuming you haven't made some overt installation error or have malfunctioning kit.


This logic doesn't make any sense to me. Why not 8v outputs then? Or 16v outputs? Voltages like those aren't uncommon in some pro audio gear.

The fact is that 2v is already overkill. So I don't see anything particularly wrong with companies that don't adopt 4v. I use a preamp in my car that's designed to be compatible with home audio, so I only get about 500mV.  In fact, it makes more sense for car audio manufacturers to try to conform to the consumer audio standard of 1v p-p than to continue to go on this path of "DUDE, MORE VOLTS IS MORE POWA WHICH IS BETTER ESSQUES"


----------



## sirbOOm (Jan 24, 2013)

Anywho...


----------



## shawnk (Jan 11, 2010)

Maylar said:


> That's correct. However...
> 
> 
> 
> ...



Good info.... Thank you!


----------



## Pitmaster (Feb 16, 2010)

Great thread!

Thank you Chad and Maylar for the lesson.


----------



## RandyJ75 (Dec 4, 2006)

Interesting thread, thanks for starting it Sirboom.


----------



## chad (Jun 30, 2005)

Many if not most of hte modern decks with DSP will make full rated voltage, flat, at 0dBFS.

But, for example alpine, if you make a boost of say "3" even at 20 KHz where NOTHING will ever really reach 0dBFS in real music. it will still pull "3" off of the top end of the volume control, meaning that on the volume control the zone between 32 and 35 is merely placebo. Cuts actually reduce volume if you go nuts. Sub all the way up is 0dB and anything lower than WFO is an attenuation.


----------



## hurrication (Dec 19, 2011)




----------



## jmacdadd (Mar 4, 2008)

All I can say is thank the audio Gods for still giving us 2V preouts...otherwise, I'd have to get RCA attenuators to run my old school amps since they only offered up to a 2V input!


----------



## Oliver (Jun 25, 2007)

sirbOOm said:


> For the same reasons people put spoilers on FWD econo cars... it adds power, bro!
> 
> (I know it doesn't add power...)


Spoilers are used for down force ( push tires for better contact ).

















(or does it............ :rockon::shocked::elvis[/QUOTE] *"DUDE, MORE VOLTS IS MORE POWA WHICH IS BETTER ESSQUES" * Everyone knows that !


----------



## chad (Jun 30, 2005)

jmacdadd said:


> All I can say is thank the audio Gods for still giving us 2V preouts...otherwise, I'd have to get RCA attenuators to run my old school amps since they only offered up to a 2V input!


Don't limit yourself, if there is a headunit you like then rock it... the 4V thing is running downhill with it's wind against it's back anyway. IF you get nervous then it's pennies to build a pad.

4V --> 2V is 3dB

Uneeda Audio - Build your own attenuator pads


----------



## IBcivic (Jan 6, 2009)

*Chad*epedia


----------

