192 khz 32 bit is not enough! 384 khz is the new
- Thread starter kristoffer
- Start date
Werner
pfm Member
A bit more. I have a true 19 bit ADC at home. If one tried really really
hard one could get to 20-21 bits for audio bandwidths.
But then you hit the limits of physics and nature. Many don't see this.
True. But this is generally unpleasant, potentially unhealthy, and quite irrelevant to the enjoyment of music in one's home.
How often do you listen to early Kraftwerk with the transducer directly connected to the bone tissue of your skull?
Even 2-5 us, and not even interaurally. That's the single one result that is potentially valid in Kunchur's work (remember?).
And entirely within the temporal accuracy of 44.1kHz sampling, of course. Even when to many this seems counterintuitive.
Purely a thought experiment, but how much LSD do we think it would take to get Jedward to hit 100kHz?
;-)
martin clark
pinko bodger
Basil I don't know, but suspect it would be an improvement (or at least inaudible)
Hah! Crank up the gramophone, grandpa!
How close to fifty were you again?
;-)
ps, I agree 100%
Pass the Horlicks, dude!
pps,
???
You mean a well mastered recording, yes?
ChristianThomas
Registered User
Think you're missing the general point.. which is purely that the human body experiences the outside world in it's entirety with all our senses. Our hearing is not the only one of our senses that can perceive changes in air pressure or vibration in general.. and that IS how we perceive music.
Well mastered doesn't mean well recorded. They are two separate stages of the music production process. Perfectly possible to well master poor recordings, technically speaking.
ChristianThomas
Registered User
Yes, it is rather over the top, and yes even different temp coefficients in gain resistors can knock off 2 or 3 bits in a 16 bit system.
But isn't the point of the extra bits to be able record at a level where the noise can be kept out of the signal. While this should all be referenced to 2V, that sort of perfection is not what happens in practice.
Ideally the recording should be looked at and, with the peak level found, your recording level is decided. But this gets adjusted for domestic listening levels on changes between tracks - or through just plain laziness in cranking out yet another CD. I'm sure that one of the reasons we greet new formats warmly is that, when they come out, the recording engineers do their best to make the most of them.
One other important aspect of the high frequency is in designing DAC filters. Designing a filter that is flat at 20kHz and is substantially rejecting everything at 22.05kHz is a demanding and skilled task. In fact I am not sure I know of anyone who has done it properly in a commercial product. But doing the same between 20kHz and 96kHz is rather easier and by 192kHz would be a breeze.
And, it brings with it the potential for an increase in bandwidth which was non-existent in CD format. Whether this is needed is a moot point but good modern amplifiers will have an available bandwidth of perhaps 200kHz, so 10x the audible bandwidth, and the op amps that we use have a GBWP of perhaps 5 to 50MHz - and we still hear the differences between them (though that's a whole other story). So there is an argument to welcome it.
But isn't the point of the extra bits to be able record at a level where the noise can be kept out of the signal. While this should all be referenced to 2V, that sort of perfection is not what happens in practice.
Ideally the recording should be looked at and, with the peak level found, your recording level is decided. But this gets adjusted for domestic listening levels on changes between tracks - or through just plain laziness in cranking out yet another CD. I'm sure that one of the reasons we greet new formats warmly is that, when they come out, the recording engineers do their best to make the most of them.
One other important aspect of the high frequency is in designing DAC filters. Designing a filter that is flat at 20kHz and is substantially rejecting everything at 22.05kHz is a demanding and skilled task. In fact I am not sure I know of anyone who has done it properly in a commercial product. But doing the same between 20kHz and 96kHz is rather easier and by 192kHz would be a breeze.
And, it brings with it the potential for an increase in bandwidth which was non-existent in CD format. Whether this is needed is a moot point but good modern amplifiers will have an available bandwidth of perhaps 200kHz, so 10x the audible bandwidth, and the op amps that we use have a GBWP of perhaps 5 to 50MHz - and we still hear the differences between them (though that's a whole other story). So there is an argument to welcome it.
Werner
pfm Member
Anyone with Matlab can do so in little time, although the result is not likely to be economically viable as a silicon implementation.
There were some bad-ish digital DAC filters in the past, when die area/cost dominated, but nowadays there is no reason not to have a mostly-decent filter on board.
Then again, the anti-imaging filter is not strictly required. Otherwise NOS would not work at all, contrary to the evidence that
1) it seems to work
2) a significant body of listeners seem to like it
When you walk away from DACs and look at software-based sample rate conversion then the last 5 years have seen the emergence of quite a few products that are nearly-perfect.
Apples and oranges.
An amplifier is a low-order minimum phase system. For it to behave blamelessly up to 20kHz it has to extend its -3dB frequency response far above 20kHz.
A digital reconstruction / anti-imaging filter is a high-order linear phase thing. Different rules apply.
So you were going for 'overly verbose' then...
;-)
To boldy record where no recording has recorded before...
ChristianThomas
Registered User
Werner
"Then again, the anti-imaging filter is not strictly required. Otherwise NOS would not work at all, contrary to the evidence that
1) it seems to work
2) a significant body of listeners seem to like it"
I was thinking more of the post DAC filter - which I'm not sure needs to be linear phase, otherwise we'd never get the rejection.
But as for whether those are necessary, I'm not sure they are either. I was fairly convinced by one could do without them when I was modding my CD player. I didn't remove the op amps, but just took out the filtery parts and it was unquestionably a step up in a reasonably fair A/B. But I didn't like what I saw on the scope so redesigned the filter and put some decent capacitors in. Now I'm not sure which I prefer, but I'm not going back to find out.
I must do some reading on NOS and whether it should work. Lots of people seem to be digging out old Philips DACs and saying they are wonderful.
On the apples and oranges bandwidth thing I'd still like to see as wide a bandwidth as possible and a decade seems a minimum to me. Where this is really bad is in loudspeakers where we will happily cross over a driver half an octave below where it gives up!
Christian
PS I noted the suspiciously Doug Self word at the end of your post.
"Then again, the anti-imaging filter is not strictly required. Otherwise NOS would not work at all, contrary to the evidence that
1) it seems to work
2) a significant body of listeners seem to like it"
I was thinking more of the post DAC filter - which I'm not sure needs to be linear phase, otherwise we'd never get the rejection.
But as for whether those are necessary, I'm not sure they are either. I was fairly convinced by one could do without them when I was modding my CD player. I didn't remove the op amps, but just took out the filtery parts and it was unquestionably a step up in a reasonably fair A/B. But I didn't like what I saw on the scope so redesigned the filter and put some decent capacitors in. Now I'm not sure which I prefer, but I'm not going back to find out.
I must do some reading on NOS and whether it should work. Lots of people seem to be digging out old Philips DACs and saying they are wonderful.
On the apples and oranges bandwidth thing I'd still like to see as wide a bandwidth as possible and a decade seems a minimum to me. Where this is really bad is in loudspeakers where we will happily cross over a driver half an octave below where it gives up!
Christian
PS I noted the suspiciously Doug Self word at the end of your post.
Werner
pfm Member
Any analogue filter following the DAC is a part of the compound reconstruction/anti-imaging filter, although it only plays the minor role of cleaning up the very high frequencies of the images left by the oversampling digital filter.
It has no reason to introduce significant non-linear phase distortion below 20kHz, and if it did, well then this could be pre-compensated in the digital oversampling filter of the DAC.
Exactly as Philips did from 1985 on.
Post-DAC analogue stages need competent design, with keen awareness
of VHF/UHV/EMI issues. That much is obvious.
But then any analogue audio stage today needs so, because of the myriad
of radio transmissions taking place ascloseasthis to the component.
What's wrong with Doug Self? It is not because he acts like the pope of
objectivism that suddenly the majority of his notions and ideas are wrong.
His books are mandatory lecture for anyone with more than a passing
interest in analogue audio electronics engineering.
ChristianThomas
Registered User
I didn't say there was anything wrong with Doug Self. I am all for an objectivist approach and feel that one of the critical tasks in hi fi design today is to bridge the gap between objectivism and subjectivism - not least to undo much of the unscientific damage done over the past 25 years or so. I think he is perfectly right to take pot shots at the subjectivist crowd dismissing measurements as 'irrelevant' by comparison to their ears.
But, by the same token, objectivists can be remarkably dismissive. Examples of this from the past include dismissing interconnects, speaker cables and now mains cables as making no possible difference. Indeed, there was a time when the prevailing view was that amplifiers were effectively identical. And the upshot of this was a retaliation with wild-eyed 'theories' about why this should not be so.
I have my own views on the preferences of the subjectivist camp which often boil down to what they are used to or what they felt comfortable with. So, for instance, the advent of CD was dismissed as being far worse than analogue because the preferred systems at that time, particularly speakers, had been balanced to make up for the deficiencies in vinyl and this was glaringly exposed by the new format. But play some of the CD players that were supposed to be not as good today - a good example would be early Meridians - and we find that they really were rather good. But the subjectivists have also contributed, and forced manufacturers to take more care (I hope) and have put the focus back on the purpose of hi fi being to bring greater enjoyment of music. Having said that, it has not been without a colossal price in the destruction of the better part of the UK hi fi industry as we bowed down to new false Gods. Unfortunately, the majority of those companies killed off were those who actually had the technical expertise that was so sadly lacking in the new wave: KEF, Quad, IMF, Celestion, Wharfedale, Rogers, Radford, Leak ... Is the UK hi fi industry better off for having Laurie Fincham and Andy Jones working in California? Absolutely not!
Doug Self can fall into this dismissive camp. For instance over the need for regulated supplies. But in his small signals book we find him wondering why he isn't getting the rejection he expects in his output stage (and says so without conclusion - though it ought to be clear to him why, as it is to me). But does this change his stance on regulation - not one jot. I fall short of your view that he is a 'must read' contributor (though I mostly do read) for this reason and because much of what he writes is not to teach but perhaps for other reasons. There is also the commercial imperative which means he withholds many of his conclusions. In this respect I would contrast him with Bob Cordell who genuinely is trying to get as much of his knowledge out there as possible, or at least get everyone up to a certain standard. But in general I concur with what a friend of mine said of Doug Self which is that the world is a better place with him in it than without him.