Originally Posted by TJElite

Not saying you're wrong, but do you have anything to document the voltage levels CD's are recorded at? I'm curious as to what that exactly means.

I'm also not sure how you would lose sound quality SOLELY because you played it back at a different voltage than it was recorded at.

What higher voltage outputs let you do is get the signal above the noise floor. This is what is called signal to noise ratio. All the electronic goodies in your car make noise. Depending on the shielding, this can be loud or quiet noise, and can make it into your RCA's, where it looks like sound to your amp, which will reproduce it. Say this noise looks like a .05 volt signal to your amps. If your headunit only puts out .5v, this is only a 10:1 SN ratio. Kick the output up to 4v, and you have 80:1.

The bigger part of this problem is when the volume is down. Since 4v is a maximum at full volume, normal listening levels are much less than 4v. Since volume is a log10 function (not linear) 1/2 volume is actually .4v, not the 2v you were probably expecting. Take the .5v example, and your down to only .05 volts...right in the noise. This is why some systems have gain hiss...that noise you hear when the headunit is turned all the way down. Many headunits actually mute the output completely at very low volumes, so you can't hear this. Many test discs contain zero bit tracks...digital silence, that you can 'play' at any volume. This is where all the ugly noises you don't think you have surface. They are always there, slightly clouding your music, you just don't notice them. This is also about the only way to isolate noises coming from the headunit, as they will be volume dependent.

Now, look at the amp gain. You set this so maximum output comes somewhere near maximum input. This becomes the sensativity of the amp. The higher the input, the lower you set your gain, the less sensative your amp is, the less that pesky noise floor gets reproduced.

Back to your statement about playing back a 4v CD at 2V. I believe that in the absense of noise, as long as you match the gains on the amp to the output of the headunit, sound quality will be the same. Its not like your compressing the dynamic range by going to a lower voltage, as the peaks and valleys of the music are all relative. That being said, I don't know everything, and if you have data showing this, I'd love to see it.

Now, do 4V units really put out 4V, maybe. I think this would depend on lots of things, like the input impedance of whatever it is driving. Also, where is the 4V measured? At the board? At the end of the pigtail? Wherever, I doubt it will still be 4V at the end of a 20ft RCA.

In any event, more voltage is better than less voltage, provided you don't exeed the inputs on the amp. Even then, you'll just end up not using the top of the volume scale.

Toby

Originally Posted by TJElite

Not saying you're wrong, but do you have anything to document the voltage levels CD's are recorded at? I'm curious as to what that exactly means.

I'm also not sure how you would lose sound quality SOLELY because you played it back at a different voltage than it was recorded at.

What higher voltage outputs let you do is get the signal above the noise floor. This is what is called signal to noise ratio. All the electronic goodies in your car make noise. Depending on the shielding, this can be loud or quiet noise, and can make it into your RCA's, where it looks like sound to your amp, which will reproduce it. Say this noise looks like a .05 volt signal to your amps. If your headunit only puts out .5v, this is only a 10:1 SN ratio. Kick the output up to 4v, and you have 80:1.

The bigger part of this problem is when the volume is down. Since 4v is a maximum at full volume, normal listening levels are much less than 4v. Since volume is a log10 function (not linear) 1/2 volume is actually .4v, not the 2v you were probably expecting. Take the .5v example, and your down to only .05 volts...right in the noise. This is why some systems have gain hiss...that noise you hear when the headunit is turned all the way down. Many headunits actually mute the output completely at very low volumes, so you can't hear this. Many test discs contain zero bit tracks...digital silence, that you can 'play' at any volume. This is where all the ugly noises you don't think you have surface. They are always there, slightly clouding your music, you just don't notice them. This is also about the only way to isolate noises coming from the headunit, as they will be volume dependent.

Now, look at the amp gain. You set this so maximum output comes somewhere near maximum input. This becomes the sensativity of the amp. The higher the input, the lower you set your gain, the less sensative your amp is, the less that pesky noise floor gets reproduced.

Back to your statement about playing back a 4v CD at 2V. I believe that in the absense of noise, as long as you match the gains on the amp to the output of the headunit, sound quality will be the same. Its not like your compressing the dynamic range by going to a lower voltage, as the peaks and valleys of the music are all relative. That being said, I don't know everything, and if you have data showing this, I'd love to see it.

Now, do 4V units really put out 4V, maybe. I think this would depend on lots of things, like the input impedance of whatever it is driving. Also, where is the 4V measured? At the board? At the end of the pigtail? Wherever, I doubt it will still be 4V at the end of a 20ft RCA.

In any event, more voltage is better than less voltage, provided you don't exeed the inputs on the amp. Even then, you'll just end up not using the top of the volume scale.

Toby

Originally Posted by GradeA_TireFryer

did you think you had to say it 2 times!! lol

Originally Posted by NoTLaDStyle

A 2v deck will not output anything buy a 2v signal. The 8v signal is normalized to 2v which regardless of noise is a loss of quality in itself.

You can view the output recording voltage by opening up the status while its ripping a CD.

Originally Posted by TJElite

Interesting...I've never thought of it before. I use EAC to rip, and I've never noticed a recording voltage...I'll have to pay more attention. I wonder if this voltage is what your sound card is seeing, what the sound card is 'outputting' or really some coded in piece of the data. Also, what is the voltage referenced to? Voltage without impedance or current is a pretty useless number.

I'm still not sure how playing back an 8v cd on a 2v deck is bad, but here's a reference that seems to say the 8v cd is bad for sound quality, in the first place.

http://www.johnvestman.com/disease.htm

Toby

Originally Posted by Miles

are you calling kenwood a liar?

Originally Posted by NoTLaDStyle

I honestly have no clue what specs the CD recording voltage is referenced to, but I know they are recorded high to retain the wide bandwidth of low bass and highs in the recording.

if the rms recording voltage was 8v then the peak volts would be something like 11v which is really high so the measurement may be off. I do know they are recorded at much higher than 2v though and when the signal is normalized you do lose detail and clarity.

Originally Posted by Ender.

Hang him!

Originally Posted by TJElite

The question then becomes how do they record them high? If they do it with more sensative mics, etc., then it might be ok. If they boost it through post production, like the link I posted describes, that would be a bad thing. I'm thinking its the latter, since live recordings usually play back quieter.

I have a program that normalizes volumes of MP3's. While doing so, it will identify the ones that are 'clipping'. I never really thought about what that meant, but it now seems that it is when the music, through post production, exceeds the gains on the mastering equipment. These songs sound 'edgy' even at low volumes. I remember that Guns n Roses and Biff Naked were some of the worst for clipping. Now that I listen to them, I can hear it. The highs just seem to garble together.

Interesting.

Toby