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Old 11th April 2012, 01:08 AM   #21
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Originally Posted by 5th element View Post
The noise floor in the acoustic = the noise floor of your listening room. It will dominate, or should dominate significantly over any noise that the system produces.
Yes of course. By my brain-ear system is able to exclude those when I focus on listening to a recording. Rather like the cocktail party effect, we're good at paying attention to some things and excluding other things - like the hum of distant trafos or whir of my neighbour's AC.

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Any fluctuations of the noise floor in the digital to analogue process should be completely masked by your room.
I think you misunderstand something fundamental about how we listen. Certainly those things can be at a higher SPL than the noise. Doesn't mean they'll be masking some effects of the DAC.

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You were complaining that a sine wave isn't representative of real music.
Nope, no complaints from me This is a hobby, its supposed to be fun! I was merely observing the fact.

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If we look at the maximum frequency sine wave that a DAC can reproduce then that should also show us the fastest rise time that any music signal could contain. Going directly from the trough to the peak of a full amplitude sine wave at this frequency should represent the worst case scenario for any transient, what came before this transient shouldn't be of any importance to the DAC.
Looks like you're talking about slew rates no? I have no interest there.

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We look at things from different ends then, but at least you want to actually be able to back up what you're hearing with a measurement.
Yes - I'm curious to learn if I can explain what I hear (subjective) with what I can measure. Its a kind of double check to ensure I don't get fooled by some kind of placebo effect Besides measurements are good marketing for a sizeable section of the audio population.

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This was in relation to what you would perhaps consider a transient effect. If you are trying to measure some sort of noise floor modulation then you should be able to do it with the DACs output held at a constant DC level. I was simply looking at it from the perspective of the DAC, it gives out a train of stepped voltages that could be looked at as a series of very quick changes in the DC level. From the point of view of the DACs internal operation and hence its noise output, does it care that the DC level has existed for only one sample or if if has existed for one hundred? If the DAC is going to do the same thing per sample, regardless of the previous sample, then you should easily be able to measure noise floor changes.

Having said this though, couldn't you simply use an analogue stage, after the DAC, that has a level of noise that vastly swamps the DACs own. Like this any noise floor modulation produced by the DAC should be completely dominated by the analogue stage. If it's modulation of the noise floor that is bothering you then surely that'd go a long way to removing it?
Seems to be a lot of conjecture - 'should' and 'surely' which doesn't look too plausible from my pov.
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Old 11th April 2012, 01:38 AM   #22
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Originally Posted by abraxalito View Post
Yes of course. By my brain-ear system is able to exclude those when I focus on listening to a recording. Rather like the cocktail party effect, we're good at paying attention to some things and excluding other things - like the hum of distant trafos or whir of my neighbour's AC.
I would argue otherwise. Noise is noise. You may be able to ignore it with your brain, but if the modulation of the noise floor is what's causing your perceived subjective observations, then if the noise floor of the room or the rest of the system swamps that of the modulated noise floor of the DAC then it is not going to be heard.

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I think you misunderstand something fundamental about how we listen. Certainly those things can be at a higher SPL than the noise. Doesn't mean they'll be masking some effects of the DAC.
No, what I understand is that these noise levels are so far down that you cannot possibly hear them, even if you were trying to. One way around you or people say that the relatively high level crud a NOS DAC throws out is 'masked' by the music, so it isn't heard. The same should then be true here for the D-S DAC who's noise is far far lower in magnitude then the crud the NOS DAC throws out. Apparently it isn't a problem for the NOS DAC so it shouldn't be a problem here.

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Originally Posted by abraxalito View Post
Looks like you're talking about slew rates no? I have no interest there.
No, I am not really talking about slew rates. You were talking about how the 'transients' in D-S DACs appear subdued compared to other DACs. If this is to be the case then surely any measurable artefact that could be responsible for this would show up better under the worst case scenario. The worst case scenario for a transient effect is going from the trough to the peak of a maximum amplitude sine wave, at the maximum frequency possible for the sampling frequency - the system cannot go any faster or harder then this.

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Originally Posted by abraxalito View Post
Seems to be a lot of conjecture - 'should' and 'surely' which doesn't look too plausible from my pov.
I weave surely and should into my sentences so that they don't come across as absolute because I am not 100% sure. You on the other hand chose to dodge the main point in favour of saying what you did. I shall restate my previous assumption then, that if one were to place an analogue stage after the D-S DAC, that had significantly more noise then the DAC itself, that any noise floor modulation produced by the DAC will be swamped by the analogue stage. If what I know about noise isn't letting me down then you should still see some noise modulation after the analogue stage, as the extra noise of the DAC will still add to that of the analogue stage, but its effect should be dramatically reduced.
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Old 11th April 2012, 02:13 AM   #23
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Quote:
Originally Posted by 5th element View Post
I would argue otherwise. Noise is noise. You may be able to ignore it with your brain, but if the modulation of the noise floor is what's causing your perceived subjective observations, then if the noise floor of the room or the rest of the system swamps that of the modulated noise floor of the DAC then it is not going to be heard.
I don't see your argument here making any sense. Rooms don't make noises, rather things like transformers and AC units and birds singing outside it do. I just got out my SPL meter as you're someone who trusts measurements. Its showing a minimum reading of 31dBA at my listening position with very occasional excursions up to 50dBA from noises outside (many windows open in my apartment as its warm here).

I know from prior measurements that I tend to listen with a maximum of below 90dBA for peaks on my meter - not particularly loud. But then I'm less than 1.5m from my speakers, they're desktop ones. By those two measurements you'd expect that anything below 31dBA coming from my speakers would be masked yes?

If so then how can I clearly hear the hiss level go up when a CD (not all CDs) starts playing? Are you going to suggest the noise on a typical CD I listen to is higher than -59dB?

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No, what I understand is that these noise levels are so far down that you cannot possibly hear them, even if you were trying to. One way around you or people say that the relatively high level crud a NOS DAC throws out is 'masked' by the music, so it isn't heard. The same should then be true here for the D-S DAC who's noise is far far lower in magnitude then the crud the NOS DAC throws out. Apparently it isn't a problem for the NOS DAC so it shouldn't be a problem here.
Seeing as its based on what looks like a misunderstanding of masking then I'll defer commenting on this until my earlier point has been addressed.

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No, I am not really talking about slew rates. You were talking about how the 'transients' in D-S DACs appear subdued compared to other DACs.
Yes and I've already explained that I wasn't talking about transients in a technical sense, rather in a subjective sense.

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If this is to be the case then surely any measurable artefact that could be responsible for this would show up better under the worst case scenario. The worst case scenario for a transient effect is going from the trough to the peak of a maximum amplitude sine wave, at the maximum frequency possible for the sampling frequency - the system cannot go any faster or harder then this.
Agreed - and how does that relate to the subjective transients I've been talking about? Like a sforzando from an orchestra?

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You on the other hand chose to dodge the main point in favour of saying what you did.
I'm unaware of dodging so please mention what you see I'm dodging.

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I shall restate my previous assumption then, that if one were to place an analogue stage after the D-S DAC, that had significantly more noise then the DAC itself, that any noise floor modulation produced by the DAC will be swamped by the analogue stage.
That's going to depend on what 'significantly more' means. I don't see this as relevant as to my knowledge the analog stage I've used when listening to my AD1955 was <-110dB for noise. That not from measurement mind, from tech specs of the opamps used.
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Old 11th April 2012, 03:56 AM   #24
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Originally Posted by abraxalito View Post
I don't see your argument here making any sense. Rooms don't make noises
I've always been under the impression that every thing in nature produces or has a certain amount of noise in it as a product of its existence. In the universe this is the background radiation left over from the big bang and acts as a fundamental amount of noise. A room too will have energy within it that acts in a similar way causing a random increase in the motion of the air particles within it causing noise as they impact on your ear drum.

As the noise is only present on some CDs then it is clearly within the recording and not a product of the reproduction chain itself.

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Originally Posted by abraxalito View Post
Seeing as its based on what looks like a misunderstanding of masking then I'll defer commenting on this until my earlier point has been addressed.
This isn't based on a misunderstanding of what masking is. Masking is quite simply when a sound that would ordinarily be apparent is made undetectable by the presence of another sound. In this case I would expect any of the music signal to be loud enough to easily mask out any minute changes in the noise floor.



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Originally Posted by abraxalito View Post
Yes and I've already explained that I wasn't talking about transients in a technical sense, rather in a subjective sense.
This doesn't make any sense, a transient is a technical objective thing that is then perceived and turned into a subjective thing. Both are part of exactly the same thing. The transient you perceive is generated by the transient recorded in the technical sense in the digital medium. If you are capable of detecting a difference in the transient produced by the replay system then this will be measurable. If this is significant then it should be more easily measured under the most extreme case. Unless by subjective transient, you aren't actually meaning a sudden change in the amplitude.



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Agreed - and how does that relate to the subjective transients I've been talking about? Like a sforzando from an orchestra?
This to me is complete nonsense. You know perfectly well how it relates to the music signal, it's an exaggerated example of what could theoretically happen given the worst case scenario for whatever it is that you are recording. This being the point. If you're not happy with this as an example I am sure we could mix in some lower frequency sine waves to make it more musical, but the rising edge of the transient wont change.



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Originally Posted by abraxalito View Post
I'm unaware of dodging so please mention what you see I'm dodging.
Instead of saying yes or no to whether or not you thought that adding in a noise source to the reproduction chain, that grossly exceeds what the DAC would produce during it's modulation of the noise floor, would or should render the noise floor modulation of the DAC a non issue, you decided to comment only on my use of 'should' or 'surely'. That was you dodging.


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Originally Posted by abraxalito View Post
That's going to depend on what 'significantly more' means.
This all depends then on how much extra noise the DAC is going to produce when it comes across a transient.

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Originally Posted by abraxalito View Post
I don't see this as relevant as to my knowledge the analog stage I've used when listening to my AD1955 was <-110dB for noise. That not from measurement mind, from tech specs of the opamps used.
This isn't the point. The point is that you would design another/ anew analogue stage on purpose so that it's noise appreciably exceeded the worst case scenario of what you assume the DAC will produce and it will thus swamp its effect out of the picture. If you do this (and you should be able to this without the hiss being a problem), then listen and you can still hear this subjective transient issue, then it would help reinforce that the noise modulation is probably not the cause.
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Old 11th April 2012, 08:23 AM   #25
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Originally Posted by 5th element View Post
I've always been under the impression that every thing in nature produces or has a certain amount of noise in it as a product of its existence.
Vibration, sure. Noise - no. Noise (or sound if you prefer) is all in the mind.

Quote:
In the universe this is the background radiation left over from the big bang and acts as a fundamental amount of noise.
Ah now you're equivocating on the word 'noise' - it has more than one meaning. Here I take it you mean 'signal that's unwanted'. When I was using the word in the context of 'rooms make no noise' I was meaning 'audible unwanted effect'.

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A room too will have energy within it that acts in a similar way causing a random increase in the motion of the air particles within it causing noise as they impact on your ear drum.
No, its not noises that impinge on my ear drums, but vibrations.

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As the noise is only present on some CDs then it is clearly within the recording and not a product of the reproduction chain itself.
I dunno if its present on CDs just some I notice and others my attention wasn't drawn to it. You're jumping to conclusions.

But where's the answer to my question about the -59dB? I'll remind you just this once as perhaps you overlooked it. If you ignore the question a second time, consider this particular discussion wound up.

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This doesn't make any sense, a transient is a technical objective thing that is then perceived and turned into a subjective thing.
But I was talking about the subjectively perceived thing. If you know precisely the elements of the objective thing that correspond to my subjective transient then go ahead and describe them. I'm all for learning more about how to describe subjective things in objective terms.

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Both are part of exactly the same thing. The transient you perceive is generated by the transient recorded in the technical sense in the digital medium.
I'd say its triggered by, not generated by. The objective (whatever it is - that's for you to pin down) gives rise to a subjective perception of a transient.

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If you are capable of detecting a difference in the transient produced by the replay system then this will be measurable.
Of that I have no doubt - but I have no idea what the measurement would need to be. Do you have any?

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This to me is complete nonsense. You know perfectly well how it relates to the music signal, it's an exaggerated example of what could theoretically happen given the worst case scenario for whatever it is that you are recording.
I find the claim that you know what I know a trifle arrogant (as well as totally mistaken) so I'll abandon this line of interaction.

Quote:
Instead of saying yes or no to whether or not you thought that adding in a noise source to the reproduction chain, that grossly exceeds what the DAC would produce during it's modulation of the noise floor, would or should render the noise floor modulation of the DAC a non issue, you decided to comment only on my use of 'should' or 'surely'. That was you dodging.
Oh I see now where you were coming from. You want an answer to the question of whether I could use an analog output stage that 'vastly swamps' the DAC's own noise. How vast is vast? 20dB? I can't see the point myself seeing as one of the big advantages I value for digital is the lower noise floor than with analog. I'd sooner use a DAC which doesn't need its noise performance vastly worsening. Why go for a low noise DAC chip only to throw away the noise advantage?
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Old 11th April 2012, 02:59 PM   #26
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Originally Posted by abraxalito View Post
Vibration, sure. Noise - no. Noise (or sound if you prefer) is all in the mind.
This is semantics, if the random vibration of the ear drum is there then there will be a back ground level of noise as perceived by our brains if we try and listen for it. Is this noise level going to be higher then the hifi systems? I don't know, but the point still stands, if this noise level is higher then the hifis then it should mask any D-S issues.

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Originally Posted by abraxalito View Post
Ah now you're equivocating on the word 'noise' - it has more than one meaning. Here I take it you mean 'signal that's unwanted'. When I was using the word in the context of 'rooms make no noise' I was meaning 'audible unwanted effect'.
No, I am not equivocating the word noise, you're just throwing up an argument which you then go on and negate all by yourself.

You say my definition of noise is = signal that is unwanted.

Your definition is - audible unwanted effect.

This is the same definition. In the first case a machine has measured some signal that is unwanted and laid it bare. In the second definition another machine has detected a signal that is unwanted, that machine being yourself.

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Originally Posted by abraxalito View Post
No, its not noises that impinge on my ear drums, but vibrations.
And no noise is created by loudspeakers either, it's just the cone vibrating. Give me a break this is like the old if a tree falls in a forest and no one is around to hear it, does it make a sound.

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I dunno if its present on CDs just some I notice and others my attention wasn't drawn to it. You're jumping to conclusions.
No I wasn't jumping to conclusions you're trying to read too much into things and putting words in my mouth when none were said. If you notice the background noise on some CDs and not on others, then it's clearly in the recording and not created by the reproduction chain.

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Originally Posted by abraxalito View Post
But where's the answer to my question about the -59dB? I'll remind you just this once as perhaps you overlooked it. If you ignore the question a second time, consider this particular discussion wound up.
As I don't know what music you were using where you can hear the noise, then I cannot unequivocally answer your question for you. But if the noise level on the CD is high enough then you will hear it. That is of course if this noise that you're talking about is a general background noise that comes as soon as you press play. I've got several classical recordings where the back ground noise is 'significant' and measures around -50dB. The only way you can answer that question for yourself is if you open the music files using a computer program and analyse them.


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Originally Posted by abraxalito View Post
But I was talking about the subjectively perceived thing. If you know precisely the elements of the objective thing that correspond to my subjective transient then go ahead and describe them. I'm all for learning more about how to describe subjective things in objective terms.
I cannot answer this question for you.


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Originally Posted by abraxalito View Post
I'd say its triggered by, not generated by. The objective (whatever it is - that's for you to pin down) gives rise to a subjective perception of a transient.
This is simply semantics.



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Of that I have no doubt - but I have no idea what the measurement would need to be. Do you have any?
Well it's nice that you have no doubts, but then again, I do. You could just be imagining this.




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I find the claim that you know what I know a trifle arrogant (as well as totally mistaken) so I'll abandon this line of interaction.
So you don't know how the maximum frequency sine wave that a system could reproduce would relate to the hardest hitting transient that that system could reproduce? This I find hard to believe, but your the one who said the assumptions I were making weren't valid.



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Oh I see now where you were coming from. You want an answer to the question of whether I could use an analog output stage that 'vastly swamps' the DAC's own noise.

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How vast is vast? 20dB?
As you're the one interested in trying to figure out where this perception of reduced transients comes from, this would be up to you to decide. If you found that you could swamp the effect by using a noisy stage after the DAC, then no doubt you'd then want to fine tune the system to figure out how much extra noise you really need. A good starting point however could probably be gained from looking at the DACs datasheet for the 0dBfs signal and using something noisier then that. Maybe the ESS datasheet showing noise vs the DC levels could be useful on setting the noise level too.


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Originally Posted by abraxalito View Post
I can't see the point myself seeing as one of the big advantages I value for digital is the lower noise floor than with analog. I'd sooner use a DAC which doesn't need its noise performance vastly worsening. Why go for a low noise DAC chip only to throw away the noise advantage?
This isn't an end point it's an experiment. Does using a noisier analogue stage remove these subjective transient effect that you can hear.
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Old 11th April 2012, 03:16 PM   #27
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I'll home in on this point about masking as its the area where ISTM you're making a fundamental error about how we hear:

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As I don't know what music you were using where you can hear the noise, then I cannot unequivocally answer your question for you.
I don't believe it makes a difference much in practice - so let's say it was one of my favourite classical CDs - a Chandos recording of 'Elijah' by Mendelssohn.

Quote:
But if the noise level on the CD is high enough then you will hear it. That is of course if this noise that you're talking about is a general background noise that comes as soon as you press play.
No, it doesn't come as soon as I hit play - that causes the CD player to seek for a short while. The noise comes after the elapsed track time starts showing i.e. when the CD player is producing non-zero bits for my DAC but the performance has yet to start.

Quote:
I've got several classical recordings where the back ground noise is 'significant' and measures around -50dB.
None of my disks are anywhere near that bad.
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Old 11th April 2012, 03:39 PM   #28
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No, it doesn't come as soon as I hit play - that causes the CD player to seek for a short while. The noise comes after the elapsed track time starts showing i.e. when the CD player is producing non-zero bits for my DAC but the performance has yet to start.
Really? You really find it necessary to actually go and explain this? It was obviously implied that what I was talking about was when the track starts playing and the DAC produces non zeros.



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None of my disks are anywhere near that bad.
Well go on then, analyse Mendelssohn's Elijah using something like Audacity and tell me what the noise level is. I can only amplify the noise at the start by around 50dB in the couple of recordings I looked at without it clipping.
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Old 11th April 2012, 03:56 PM   #29
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Well go on then, analyse Mendelssohn's Elijah using something like Audacity and tell me what the noise level is.
As I don't have that particular CD on this computer, here's the first 4s of another classical CD - Rattle's Beethoven 2nd Symphony, Vienna Phil. Its had 50dB gain applied. The extent of the window (vertically) is the full scale.
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File Type: png Beethoven symph 50dB gain.png (3.0 KB, 169 views)
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Old 11th April 2012, 05:10 PM   #30
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The noise comes after the elapsed track time starts showing i.e. when the CD player is producing non-zero bits for my DAC but the performance has yet to start.
That's 4 seconds? You say that the DAC anticipates that the music will start playing in the next two seconds and raises the noise? That implies that it has some kind of time-delay line, buffer memory. Or has some other kind of time-travel device inside.

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