[neekomax]

I've seen it mentioned that digital volume controls remove information from the signal, therefore lowering sound quality (ie 16 bits -> 15 bits...).

Then I hear that from iTunes 7 and on, it's fine to use the volume slider, they changed how it works.

So which is it? How does it work? What do you recommend?

(I have remote controlled volume on my preamp, but it's very sensitive, and I'd like to be able to fine tune volume using iTunes, but won't until I get the audiophile seal of approval ) 

[ultrafi]

In a 16 bit system, after about 20 dB of attenuation and you're throwing away bits.  Sonically, I and others generally find less than this is better, more around 6 dB.

Dunno, where you got the after iTunes 7 stuff; but, it still doesn't sound good.

Best to avoid the slider all together.

[neekomax]

From here, and others referencing it: http://www.benchmarkmedia.com/wiki/index.php/ITunes-QuickTime_for_Mac_-_Setup_Guide

Here's one of the relevant parts:

Set iTunes volume to "Full"

Volume settings below "full" may cause severe distortion, especially on version 6 and earlier.

The volume controls in iTunes versions 7.X and 8.X will not cause significant distortion. The user should not hesitate to use the volume control in iTunes v7.x and 8.X

This does not refer to the track-specific "Volume Adjustment" settings found in the "Get Info" menu. The "Volume Adjustment" setting should always be set to "None" for all tracks.

When they say 'don't hesitate', that means the sound is unaffected, right? I mean they make 24 bit DACs for a living...

[srb]

When they say 'don't hesitate', that means the sound is unaffected, right?

No, they don't say the sound is unaffected, they say that the volume control won't cause significant "distortion".  I have played with the iTunes volume control quite a bit and while I'm not necessarily hearing distortion, I find that dynamics and punch seem to be reduced.  Perhaps the signal to noise ratio is reduced and noise floor increased as well, but that is harder to discern than the flatness (dynamics, not frequency response) of the sound.
 
I have a few Airport Express that I use for casual listening and will sometimes use the AirPlay volume controls on them for convenience, but when I listen to these modest systems in other rooms a little more seriously than casually, I will run their iTunes volume controls at 100%.
 
My understanding is that some of the premium software players like Pure Music have higher bit and/or dithered volume controls that have less of an effect than the iTunes volume control.
 
Steve
 

[neekomax]

Ok thanks, I think I get it. There's no getting around the way digital attenuation works, it is simply reducing information. Benchmark thing had me a little confused.

[nnck]

This is an interesting topic to me and I have a somewhat related question.

I realize an ipod or iphone may not be the best device to use in a hi-end audio system, but I sometimes hook it up to the hi-fi for convenience. So I was curious if the volume slide control on an my ipod touch and iphone 4 work in a similar way to what is being said here about itunes.

i.e. Is it always best to keep the ipod/iphone volume slide control fully maxed out and use the volume control on the preamp to control the volume? Do you lose infomration if you use the volume slide control on the ipod/iphone to lower the volume there?

In some instances I feel that I am hearing excesssive distortions from my audio systems when the ipod/iphone volume is maxed out, so I sometimes lower the volume slider a bit. Then I fine tune the volume with the preamp's control. Is this a bad idea?

[srb]

In some instances I feel that I am hearing excesssive distortions from my audio systems when the ipod/iphone volume is maxed out, so I sometimes lower the volume slider a bit. Then I fine tune the volume with the preamp's control. Is this a bad idea?

If you are getting distortion with the volume control maxed out, it sounds to me like you might be using the amplified headphone jack for your output?  If so, yes, that amplified headphone output can be driven to distortion and/or overload the line inputs on your preamp.
 
A better way would be to use the line output from the iPod's dock connector, which can be accessed from one of the many available iPod docks or Line Out Dock (LOD) cables with the iPod's volume control maxed out.
 
Steve

[SLC]

It has been my experience that you can cause distortion in Itunes by by pushing the EQ to hard. Watch that preamp setting in the equalizer I set mine at about -3db.

[neekomax]

It has been my experience that you can cause distortion in Itunes by by pushing the EQ to hard. Watch that preamp setting in the equalizer I set mine at about -3db.

Everything I've seen or heard indicates that all eq/sound enhancer/gain in iTunes should be avoided completely. EQ should be turned off.

[SLC]

Everything I've seen or heard indicates that all eq/sound enhancer/gain in iTunes should be avoided completely. EQ should be turned off.

I use the EQ all the time with no noticeable ill effects other than what I mentioned above.