iTunes Volume Control on OS X

[The Computer Audiophile]

Hey guys - I got a DAC in this afternoon that is HDCD compatible and has an indicator light when I pass an HDCD song through it. To my surprise the iTunes volume control does effect the audio signal enough not to pass the complete HDCD signal to the DAC. When the iTunes volume is at 100% the HDCD indicator lights up. When I adjust the volume to anything lower than 100% the indicator goes dark.

 

With some manufacturers saying iTunes volume control works fine and other suggesting it's rubbish it is hard to know what is really going on. I guess it took some personal experience and experimentation to make my own decision about whether or not to use the iTunes Volume control. Sure I could have completed additional listening tests, but with the facts right in front of me I won't be wasting any time on that.

 

So, despite contradictory information about the iTunes volume control I will no longer recommend that anyone use it for bit perfect sound. If you're not too worried about bit perfect sound in a non-listening room situation then the iTunes volume control will be just fine for you. In a serious listening situation where you want the best quality the iTunes volume control should be off limits.

 

This information is based on iTunes version 7.6.2 (9) and Mac OS X 10.5.3

 

[JonathanCatuccio]

Chris,

 

If we attenuate with a 32bit internal volume control aren't we losing 1bit per every 6db. I fail to see what is really lost given the amount the bits we start with on most recordings. Frequencies reporucxtion isn't changing, and amplitude isn't changing relatively between freqs.

 

So why is bit-perfect touted as superior. I doubt that anyone would notice a 10db digital attenuation applied via something like EMU Patchmix of J. River volume control.

 

DC

 

[The Computer Audiophile]

Hi DC - Everything is subjective and we all don't have the same goals in terms of our audio playback systems. Personally I strive to playback the exact bit for bit track that is on the original recording. To me bit perfect is superior because it is exactly what the artists intended. Any change in this no mater how evident or not is still a change from the original recording.

 

Reference Recordings 24/176.4 HRx albums sound fantastic and are as close to a real performance as I have ever heard. I don't want to make any system adjustments that output anything other than the exact file as RR released it.

 

There is on right or wrong or better or worse here, it's all up to each individual to make their own decision. As is often said around here, if it sounds good to you that's all that matters.

 

Good discussion though.

 

[BEEMB]

Chris,

 

Is that a 'dont use I-Tunes' or simply the volume control within I-Tunes .. ?

 

What is Front Row doing to my music ? That's no the I-Tunes volume - could you try that too ?

 

Regards,

 

 

MAtt.

 

[The Computer Audiophile]

Hey Matt - Just the volume control in iTunes effects bit perfect playback. iTunes itself is great. I'll give front row a shot to see what it does. After all it's just a flashy interface that uses the same stuff behind the scenes. I'll let you know what happens.

 

[rom661]

Hey Chris

But it is very handy when you are using an iTouch and the phone rings...

 

I agree with your conclusion but came to it by doing level matched, within .1 db, comparisons with a mild volume reduction via iTunes compared to the same SPL reduction provided by a Levinson preamp that does .1 db volume increments.

 

Rick

 

[Wavelength]

Guys,

 

The way it works is pretty much the same for all PC and MAC applications.

 

At least in iTunes if vol=100% then this calculation is not done.

 

But all samples are converted to float32 bit. If the vol control != 100% then then the following type calculation is preformed:

 

output = (Sample*Volume Setting)

 

Since Volume Setting would be less than 1 the thought is that the "output" is going too loose valuable low level information.

 

Hey Chris... does the iPhone - iTunes interface allow changing the system volume control like the remote does? Just wondering for the Proton as the line and headphone outputs are tied to the system volume control.

 

FYI guys... if you enumerate a USB device to have a hardware volume control and that is selected as the master output then the system volume control will signal the dac to control the volume and will keep intact the bit perfect data stream going to the dac.

 

Thanks

Gordon

 

[JonathanCatuccio]

Gordon,

 

Are you saying if we lower a 32bit digital volume control to say 90%, we lose information?

 

I thought that for every 6db of attenuation, 1bit is lost.

 

Given the above scenario, what is actually "lost" if a DSP is set to use 32bit for playback and uses a 32bit volume control.

 

Seems like some minor attenuation in something like EMU patchmix, if needed would not adversely affect the fidelity (while it may be in fact not bit-perfect).

 

 

DC

 

[Wavelength]

Gang,

 

Using the volume control will always change the character of the sound. While it use to be much worse when these players would use fixed math and then go floating point.

 

The point is this is not the place to be adjusting the volume. It's always best to be doing this in the analog domain where nothing will be lost.

 

Thanks

Gordon

 

[JonathanCatuccio]

How is audible? How is the character altered if the bits are under the audible threshold? I have read some stuff from Dan Lavry about very low amplitudes being audible, but that needs more review.

 

Now if you mean by "using the volume control" as the Master then maybe because then one would be seriously attenuating when running internal digital volumes at 5-10%. Your statement is rather a blanket generalization and I would honest expect a little more scientific discussion from someone of your caliber. You mean understand the numbers behind all this, but you need to elaborate for me and many other readers here, rather than just qualitative exposition regarding the beliefs you hold. I'm being very specific: "Seems like some minor attenuation in something like EMU patchmix, if needed would not adversely affect the fidelity (while it may be in fact not bit-perfect)." You, unfortunately, are not.

 

JC

 

DVDdoug said:

 

http://www.hydrogenaudio.org/forums/index.php?s=b62f59a82b520d846019b40ee7c32ad0&showtopic=65521&pid=584990&st=0entry584990

 

"When you attenuate, all of the lost data is at the "quiet end". So, even if you could keep the lost details/data, these details would be be attenuated below the "old" 1-bit level. (In fact, you can preserve the details if you use floating-point, but you're still not going to hear anything different.)

 

Something similar happens with an analog volume control. The "lost details" fall-into the noise or below the threshold of audibility.

 

So, you can digitally attenuate a signal 20 or 30 dB (or as much as you want), and you don't hear any "distortion". You can attenuate it 'till you're down to 1-bit remaining, which would be really lousy audio, but you won't hear anything anyway!

 

However, if you re-amplify the signal (digitally or by turning-up the volume control on an analog amplifer) you might hear the effects, but you're probably not going to hear any ill-effects with normal adjustments (i.e. 10dB) at 24-bits."

 

 

 

 

[The Computer Audiophile]

Hi guys - this is a really interesting topic. Gordon and JC - you guys are talking about the same subject matter, but your not discussing apple and apples.

 

I believe Gordon is talking about a "best practices" approach and achieving bit perfect playback.

 

I believe JC is talking about the science behind volume attenuation followed by a somewhat subjective factor of what someone should or shouldn't hear. I only bring in the subjective part because at a certain level of attenuation it appears that sound degradation can become audible and once this is in play it is up to each listener to decide if they can hear it or not.

 

On a related note. We are not talking about life and death here. The tone of this discussion just got real serious real quick. This is a laid back site that brings enjoyment to all the readers. When conversations get accusatory and some less than collegial comments are made it is no longer fun for anyone. I am all about sharing honest opinions and leaving decisions about what to believe up to each reader.

 

[JonathanCatuccio]

If I came off as harsh or less than collegial, I apologize. I'm trying push for a little for a little less "opinion" and "idea" and focus of matters of fact. We can collectively and accurately make assessments of objective reality if we gather empirical data and share it. Yet, everything we experience is subjective, our personal representations all differ, but if we communicate and dig a bit deeper and refine our positions and compare notes, we can compare thousands upon thousands of subjective experiences and form a pretty damn accurate picture of the world around us. This I believe is at the root of the deductive-inductive ebb & flow of scientific knowledge. I'm am positive that Gordon knows much more than I do about these matters, but I felt that his comments bordered on rhetorical dogma, that's my opinion ; ) That's fine, if you at least then say, "and hey read this here about this etc."

 

Jonathan Catuccio

 

[The Computer Audiophile]

Hey thanks Jonathan.

 

[Innertuber]

Funny, my neighbors never say "Make that music bit perfect." I have heard them say "Turn it down". They don't care whether I do that via analog, digital, or close the doors and windows. By that time I don't have much of a preference either.

 

[machinehead]

I don't mean to sound like a total nuub, but can't help it.

Where do I adjust the "iTunes Volume"?

I see when you "Get Info" from a song in iTunes, you can adjust from -100 to +100 volume, but not iTunes in general.

I am streaming to an Apple TV, will this still effect bit perfect output?

 

Thanks,

 

Jeff

 

[machinehead]

Duh!

 

I can't believe I never have seen the vol. slider in iTunes!

How many years has iTunes been out!

Man, I need to slow down on the caffeine and enjoy the music.

 

Thanks guys for pointing this out!

 

Jeff

 

[PeterSt]

[deleted my post]

 

I just realized that you guys are not waiting for any technical insight. Maybe later, maybe never.

:-)

Peter

 

[The Computer Audiophile]

Did I miss something here Peter? I don't see your post.

 

[PeterSt]

Hi Chris,

 

Afterwards I saw that you may have gotten the idea that my post got deleted (e.g. by you). No, I deleted it myself. Okay, deleted the contents, because I didn't see a delete option.

 

Although I tried to answer the question (digital volume), I felt it was kind of inappropriate and thought it was time to stop "outbettering" others' answers. Also, for me, it always needs the reference to XXHighEnd and I thought I had done that one time too many now.

 

On another note, though related, I see that the audience you have here is so much focused on iTunes and MACs and all, that I start to feel an intruder, really. And, I hope I can say it, I also don't see any relation with all this and real high end music playback by means of computers. By no means I imply that people here don't have ears and instead many will have better audio playback systems than I have, outside of computers. But I do get the feeling that here it is about getting music playback to computers because of conveniency, and not because it would be better for sound quality. Explicitly better.

 

Before you say it yourself, it could well be that you auditioning Amarra opened your eyes a bit that software and the (tweaked) environment it operates in, *does* matter. That is, I recall you saying so the other day. This also implies, that before you might have had other ideas about this, which is the reason this great forum didn't head towards what it should have, according the context of its name : audiophile playback by means of computers. Don't get me wrong please; it is by now full of great people with the gift of being able to discuss at the higher level about often very good subjects, in a way "we" feel very comfortable. The same comfort comes to those who need help in setting up their first computer playback system in an atmosphere which is just the best.

 

When I jump in, I feel that I am shouting in a way AA is known for. I never go there because I don't like shouting, and most certainly don't like all those who only copy words from others without knowing. So indeed, the opposite of laid back. When someone like me is too profoundly telling the same things, though each time from maybe another angle, this is shouting. Not laid back anymore.

All 'n all it slipped through my mind that Gordon - who did not respond anymore in this thread - was "outbettered" by me, and that in the end this is not much respectful and the first reason to delete my post.

 

With the latter in mind, I think you'll understand. Who am I to be better than others ?

 

Peter

 

[BEEMB]

Peter,

 

Your last comment "who am I to be better than others" .. such a good question.

 

Maybe you're slightly misled, maybe you're not. I am interested in learning why you believe that use of a Mac and I-Tunes (on a Mac) is more about convenience than high end audio output.

 

Why is XXHighEnd the only way to achieve high end output on a computer ? iTunes on a Mac is apparently bit perfect - I'm willing to learn.

 

There are many PC users preferring Foobar (if you approach the author he'll also tell you it's written with a minimal footprint for ultimate audio quality) to XXHighEnd also.

 

I'm talking audio quality here, not convenience. I'm inviting you to tell us all why your software is so much better (in your opinion), since many on here have the equal of your setup (Lynx vs FF) and I guess some may have better.

 

If we ever get on to the subject of convenience then there is a clear winner !!!

 

 

Matt.

 

 

 

[PeterSt]

There are many PC users preferring Foobar (if you approach the author he'll also tell you it's written with a minimal footprint for ultimate audio quality)

 

Hahaha Matt, you coudln't be more wrong. Indirectly ...

Now *you* approach the author (Peter) from Foobar, and watch closely how long it takes before you're slammed because software just cannot make a difference. In this case you don't even need to come up with triple (does that exist ?) ABX etc., because it just can't.

 

For your fun : http://www.hydrogenaudio.org/forums/index.php?showtopic=64392

The thread got closed within a couple of hours.

 

Foobar is not alone on this : http://www.un4seen.com/forum/?topic=8980.0;all

 

At the same time there is your answer; how would you think such a player would improve on having the best sound quality if the auhtors don't believe in it in the first place ?

 

And this is exactly what the difference makes;

Of course there's a LOT one can do about the environment, but when I finished that myself (which really took me over a whole year !) it came to me that no matter how bit perfect all was, it sounded different, and not good in any case (TheaterTek (which is a video player) and WaveLab5 (which is merely an analyser) came closest. Well, the story is known, I wrote my own player with the explicit *thought* that I would be able to make the difference, just because all players already proved there could be.

So why is XXHighEnd better ? simple answer is : because I explicitly work on sound quality, with btw great help of all my users, who just teach me in hearing things/differences, just as well as I teach them.

 

Really, if you think that "bit perfect" is the only prerequisite ... it is just not (and I explained earlier that Engine#1 of XX even doesn't play bit perfect, and is still appreciated better than anything else (which I find difficult to say myself)).

 

That I am the only phool on this globe who ever started to think software could matter and work on it, is just a coincidence of having equipment making it audible, being a systems programmer for nearly all of my life, and added to that, that always performing the impossible is part of my living, and I had some spare time to do it. Oh, and being an audiophool helps. Anyway, a combination not everybody has.

Btw, I was the only one for 18 months or so, and AFAIK there's only cics doing similarly : http://www.audioasylum.com/forums/pcaudio/messages/2/27041.html

Keep in mind, what cMP does is creating the environment for you, the user, which is only the half part of what XX does. So, XX does exactly the same (making the OS more lean) but in another way, keeping the PC a normal PC. The other half (which cics tries to approach as well : http://www.audioasylum.com/forums/pcaudio/messages/3/31286.html ) is much much more complicated, and not addressed by anyone but me (as far as I kno that is), and this is my means to influence the DAC. And no, I won't tell how :-) but for that it took me over a year to learn what to do to get it in which direction, after I found out about it at first.

 

I listen to my users unconditionally. They are (somehow) all in the same leage or became part of it, and what they claim they hear, I can hear too. This is rarely related to the equipment used, and a charachter of sound can deploy in any system, some even claim in their PC speakers. The way "we" listen has to be learned, and many many things I did not know of myself a few years ago. I mean, without knowing those you won't hear the absolute difference, and the only thing which is left then, is "foot tapping" or not. Indeed this is a means by itself, but there's always a foundation, and I never rest until I found that (only then it can be controlled in a direction).

 

The fact that everybody always hear the same changes, is the most convenient for further development.

FYI (oh well, because it just *is* interesting) it happened one time that 5 or so users voted for an older (I think it was 0.9d) version, and another 5 voted for a newer (0.9h whatever) and each group had their own arguments. I belonged to the last group, but after really weeks of time I started to hear what the first group meant. Remember, this is all by words over the internet, and that is great sport by itself.

Although each version keeps on being available for later reference (which is an explicit means to proceed on SQ), of course a newer version has added functionalities. So, in this case I had to solve something.

For your entertainment, but also the proof that even huge differences can emerge by means of software : http://www.phasure.com/index.php?topic=180.0

 

Btw, this last link may show better how I deal with it, than all words in here. :-)

Peter

(who just did it again)

 

[Innertuber]

Innertuber

[PeterSt]

Now I don't know what your Huh is about, but if it is about what Chris said ...

 

I've always thought iTunes and the list of other applications sound very good. Until I heard the difference Amarra made at RMAF 2008.

 

If it is about the remainder of your quote, well, that is my perception (which is personal of course), but related to the quote above from Chris obviously. So, it depends on what one's references are. Chris' reference probably just changed. :-)

 

Not that it is necessary to discuss this. I just expressed my feelings. Let's not make a big deal of that.

 

Peter

 

[BEEMB]

Peter,

 

I don't mean to be rude but I think a number of us are struggling with your English.

 

Never once have I said that software doesn't make a difference. It does, especially on the PC. And you're not the only person to ever think that. XXHighOpinion ?!

 

Okay, so you're stating that bit perfect is not the only thing that's important. I don't understand this. Surely we all want to get a perfect digital audio stream, untouched if possible, to our external DACs. I don't know what you're doing to the sound within XXHighEnd (tell us please) but your engine is surely playing with it. It's great that development takes place based on user input, but to suggest that your users are all in some amazing audiophile league is some statement (oo, I replaced tosh with statement) .. There are many users on here that ARE, without fail, in the same league as yourself or greater - we have manufacturers on here !!

 

What is your engine doing and why should that better the output ? Why is that better than a perfect audio stream going to an external DAC ?? I'm interested, I wish to learn and I wish to then discuss.

 

I understood and know that your software loads audio data into RAM before playing - removing the audio jitter that you may have from the hard drive (which is far less than from even an expensive CD player I assume - oh, and all your error correction is done prior to actually using the file on the hard disk - none of that happens on the fly as with a CD player) ...but okay, agree, RAM better than a hard drive (unless its solid state of course). So CMPlay and XMPlayer are doing the same too - but they work with existing programs, right ??

 

Okay ... so, tell us what your audio engine is doing. I see the benefit of loading into RAM, I really do ... but I don't see why you should be altering the sound. Are you resampling in software ?

 

I have downloaded and am trying to use your player but all my files are in AIFF format. I've tried a few but I'm sorry to report that I'm having trouble getting it to work properly. I spent a while tinkering but heck - I can plug iTunes into Foobar for a decent sound and have usability (I'm not saying a better sound than XXHighEnd) ... loading into memory is the only thing I'm missing then, surely.

 

If your engines are that good, and I really need to hear it. then please make this into a plug-in that works with other software ? People will pay if it's that good. Get programming !

 

Bit perfect sounds different; that's been mentioned on here a few times - by Chris himself .. What is your engine doing to the sound.

 

I'm going to have to get it working with my PC so I can move into your league. ;-)

 

And I'll be forever thankful to Chris that such a website exists that allows both new users and more experienced users alike to communicate without *shouting* at each other.

 

 

 

[BEEMB]

 

Peter,

 

Again, your response to Chris. I think most people on here know that the software makes a difference.

 

Most, if not all....

 

Otherwise we'd all be using Windows Media Player.