Digital, but not by the numbers

[Julf]

Originally Posted by Charles

the Tera-Player does not oversample at all, I just wanted to explain that resolution achieved through time-averaging cannot be compared with real static resolution.

How does that correspond with what you said earlier?

Originally Posted by Charles

If this were the case, I could also say, that the 16-bit static resolution of the Philips is really a 64-bit time-averaging resolution, just because I speed up the sample-rate ... and am thus able to generate levels between the 16-bit quantization.

So do you "speed up" the sample rate, or not?

[abraxalito]

Obviously he doesn't speed up the sample rate - look at the sentence construction in detail - its conditional - 'I could also say that...'. He also makes clear there's no oversampling. Clear to me anyway

[qusp]

Originally Posted by abraxalito

Is your question directed at Charles for an answer?

As for me, I don't go down the road of using opamp feedback in the I/V circuit. I have no objection to opamps but seems to me that jamming a very fast rise time analog ( are you reading this marce - analog!) signal into an LTP is asking for overload. Barry Gilbert seems to be saying that when he touches on the subject and I see no reason to doubt him.

For Charles, since hes making such a big deal about SD dacs making up stuff and R2R, which of course the dac is not? being able to produce with single digits (the equivalent of having its hands tied behind its back) a much more linear real representation of music, I just wondered what happens to this real stream of real musical bits when its fed to an opamp...

I dont mind opamps either, they can be used to good effect, i'm not making comment against them, but at such low gains there is a LOT of feedback going on. I wondered how he can be so precious about the 'fake bits' when an opamp uses a far from linear process to amplify, yet somehow this is acceptable....

also the magic ears come out....yeah, your ears can make marvelous worldbeating music from 4 bits that I cannot dream of experiencing with the full 16 bits left after I turn the volume down very low

during all of this we are assuming perfect analogue performance from your IV and headphone amp running on 3.7v that lasts for 12+ hrs on a 700mah battery... seems pretty unlikely to me...

[Trevor White]

Originally Posted by Charles

Hi Julf,

the Tera-Player does not oversample at all, I just wanted to explain that resolution achieved through time-averaging cannot be compared with real static resolution.

Therefore the resolution of a sigma-delta DAC is a pseudo-resolution compared to the resolution of a R2R DAC, which is a true resolution.

Charles

Those are absurd arguments !! When you use an analog reconstruction filter aren't you doing time averaging ??

[Trevor White]

Originally Posted by abraxalito

Obviously he doesn't speed up the sample rate - look at the sentence construction in detail - its conditional - 'I could also say that...'. He also makes clear there's no oversampling. Clear to me anyway

and what does he use for a reconstruction filter and what does he do about those pesky aliasing components ?

[abraxalito]

Originally Posted by Trevor White

and what does he use for a reconstruction filter and what does he do about those pesky aliasing components ?

Why ask me?

NOS has imaging components, not aliasing - I can tell you that

[abraxalito]

Originally Posted by qusp

For Charles, since hes making such a big deal about SD dacs making up stuff and R2R, which of course the dac is not?

Charles has a valid point about resolution - why are S-D DACs marketed with the high resolutions that they claim for them? Since they all suffer from noise modulation - meaning the noise varies with the signal level - they cannot have a constant resolution. Resolution means the ability to resolve, tell the difference, between two things. But with an S-D this ability to resolve two different input codes depends on signal level. At lower signals, the resolution is higher than at higher levels.

I dont mind opamps either, they can be used to good effect, i'm not making comment against them, but at such low gains there is a LOT of feedback going on. I wondered how he can be so precious about the 'fake bits' when an opamp uses a far from linear process to amplify, yet somehow this is acceptable....

The opamp non-linearity would be a different thing - it produces IMD products which are fairly well characterised in terms of their correlation with signal. S-D noise modulation is not, and the datasheets don't give this information in any form, apart from ESS who indicate how SNR changes with DC offset if I recall correctly. S-D incorporates feedback too - around a much more serious non-linearity than any I've seen in an opamp.

[qusp]

irrelevant and you missed my point, I didnt say it was the same thing, just that such concerns over signal that can be compared the input and deemed very faithful even with volume turned down on the digital control, yet this is criticized to replace with 4 bit signal?, which cannot hope to attain anywhere close to a replica, nomatter the 'purity' of the representation of the SD sampled wave (is there anything else?).... concerns about linearity... really? though a different mechanism, feedback in the form used by an opamp to recreate a good result at the output is not even close to linear, just listen to the feedback by itself and see how it smooths over time and error through feedback, yet the result is acceptable? hifi even. its a red herring...

we havent even touched on the problems of the analogue stages and only one obvious farfie has been corrected, still the subject of what type of dac it is has been dodged, along with the 'resolution, which seems to be a deliberate misrepresentation given its clearly acknowledged to simply be a careful choice of words...how can its (the dacs) operation be known if its type is not known?is it R2R?. lets have a look at the output at 50% volume with a lowZ load?

still waiting for someone to show me anything but an SD ADC, this dac can differentiate the distinct musical samples again?

[abraxalito]

You want a non-SD ADC? There are many, just go to ADI's website and check out the ADCs which are not for audio purpose. There are 16+bit ones with SFDRs in the 100dB range and sample rates up to 1MHz or so. Only yesterday I noticed Linear Technology had a banner ad for a 2.5MSPs 18bit one.

As for the DAC, Philips don't' make many so its either a TDA1545 or TDA1387.

[qusp]

Originally Posted by abraxalito

You want a non-SD ADC? There are many, just go to ADI's website and check out the ADCs which are not for audio purpose. There are 16+bit ones with SFDRs in the 100dB range and sample rates up to 1MHz or so. Only yesterday I noticed Linear Technology had a banner ad for a 2.5MSPs 18bit one.

As for the DAC, Philips don't' make many so its either a TDA1545 or TDA1387.

not really, my comment simply related to just about every single piece of music will be sampled with SD already, so what can a non SD dac do about this problem of which you speak to make these distinct samples again? its a red herring

re the dac, I know that, but its still supposed to be R2R according to the claims. I guessed it at the 45 straight after it was released. not much can operate on such tiny voltage, tiny current and without large complexity thats impossible in a little portable.

anyway how about we leave it, nothing is going to change my mind here, my stance is the same as going in, just now its all been confirmed from the horses mouth.