Fokus Posted July 17, 2017 Share Posted July 17, 2017 52 minutes ago, Jud said: Would ultrasonic ringing be subject to the same potential problem as ultrasonic aliasing, intermodulation distortion? No. Because with real music the evil ringing is not there for most of the time, and when it is there, it is very faint. 'ultrasonic aliasing' is a misnomer. I assume you mean the creation of ultrasonic images from the baseband due to inadequate reconstruction filtering during replay? That is 'imaging', not 'aliasing'. Aliasing is when you go down in sample rate (or sample an analogue signal). Imaging is when you go up in sample rate (or do the final conversion to analogue). Many publications get this wrong, hence the wide spread of this mistake. Ultrasonic imaging starts with the same amplitude as the baseband. So in NOS DACs and in leaky-filter DACs it can be appreciable. esldude 1 Link to comment
mansr Posted July 17, 2017 Share Posted July 17, 2017 51 minutes ago, Jud said: 1. Does the output of the MQA filtering in the DAC (a) go through the same upsampling to 8x rates and SDM as any other signal, or (b) bypass the normal upsampling and SDM? All MQA DACs I know of are based on ESS or TI/BB chips operated in standard PCM mode. The decoded MQA "core" is upsampled using MQA's weird filters to the highest rate possible as constrained by DAC chip capabilities and microcontroller processing power. From there on it's standard SDM as always. 51 minutes ago, Jud said: 2. If the answer to 1(a) is yes, does someone (Archimago or anyone else) have measurements showing any difference in analog output of a DAC vs. non-MQA? Do you mean difference in an MQA DAC when playing normal content vs MQA? Of course it's different, mainly in the presence of high-frequency images and dither noise. esldude 1 Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 19 minutes ago, Jud said: In linear phase filters, time through the filter does not vary by frequency. In minimum phase filters, group delay is minimized but varies by frequency. Hi, Thanks - but if the phase changes with frequency, and we have two signals in synchronisation, 100Hz and 10kHz, the 100Hz has no delay (0deg phase) but the 10kHz signal has 45deg phase (assume lag) and this introduces a 12.5uS delay ? Regards, Shadders. Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 23 minutes ago, Fokus said: Linear phase = constant (time) delay over the entire frequency band. If you have 45 degrees at 10kHz, then you'll find 0.45 degrees at 100Hz. No phase distortion. No temporal distortion. It are the minimum phase filters so beloved by Meridian/MQA that cause phase distortion. Not that this matters much. Hi, Thanks- have responded to Jud on this. Regards, Shadders. Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 23 minutes ago, Shadders said: Hi, Thanks - but if the phase changes with frequency, and we have two signals in synchronisation, 100Hz and 10kHz, the 100Hz has no delay (0deg phase) but the 10kHz signal has 45deg phase (assume lag) and this introduces a 12.5uS delay ? Regards, Shadders. I don’t know what the specific delays are, but yes, a minimum phase filter delays one frequency more than another, so it is a “dispersive” filter. This is thought by some people to possibly give an illusion of depth. One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 5 minutes ago, Jud said: I don’t know what the specific delays are, but yes, a minimum phase filter delays one frequency more than another, so it is a “dispersive” filter. This is thought by some people to possibly give an illusion of depth. Hi, Are you sure this is correct. If the filter is an all pass, then all frequencies have the same delay (minimal group group delay) in the frequency range of interest. So a minimal phase filter may delay one frequency more than another (but minimally), but a linear phase filter incurs greater phase changes (assumed) albeit linearly with frequency. Is a minimal phase filter called as such, since its phase change is less than other filters such as linear phase ?. A phase change will equal time delay for that signal. They represent the same thing ? Regards, Shadders. Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 32 minutes ago, mansr said: Do you mean difference in an MQA DAC when playing normal content vs MQA? Of course it's different, mainly in the presence of high-frequency images and dither noise. Interesting, I didn’t know whether some of the MQA ultrasonics might be removed in the process of upsampling to 8x (or higher) rates, SDM, and final reconstruction filtering. If I remember correctly, you didn’t think the levels of ultrasonics you were seeing with MQA would be particularly audible. Anything change your mind since? One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 2 minutes ago, Shadders said: Are you sure this is correct. Yep. One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 4 minutes ago, Jud said: Yep. Hi, Thanks - just looked up the wiki - states linear phase has constant group delay - so i need to check this out. Regards, Shadders. Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 4 minutes ago, Shadders said: but a linear phase filter incurs greater phase changes (assumed) albeit linearly with frequency. Is a minimal phase filter called as such, since its phase change is less than other filters such as linear phase ?. A phase change will equal time delay for that signal. They represent the same thing ? Regards, Shadders. The *time delay* is constant over frequency with a linear phase filter. Of course, as Fokus points out, equal time means different fractions of the wave at different frequencies. One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
mansr Posted July 17, 2017 Share Posted July 17, 2017 7 minutes ago, Shadders said: Are you sure this is correct. If the filter is an all pass, then all frequencies have the same delay (minimal group group delay) in the frequency range of interest. An all-pass filter is any filter with flat amplitude response across all frequencies. The phase response can be anything. Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 8 minutes ago, Jud said: The *time delay* is constant over frequency with a linear phase filter. Of course, as Fokus points out, equal time means different fractions of the wave at different frequencies. Note that this keeps the time and phase *relationships* between different frequencies constant. These relationships are altered by minimum phase filters. (How is the ultrasonic ringing “pushed” later in time than the main impulse?) One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 5 minutes ago, mansr said: An all-pass filter is any filter with flat amplitude response across all frequencies. The phase response can be anything. Hi, Thanks - yes - just looked up the book i have - constant time delay, but varying phase delay. The group delay graphs for the various orders are constant. I need to examine more closely. Regards, Shadders. Link to comment
Hifi Bob Posted July 17, 2017 Share Posted July 17, 2017 1 hour ago, mansr said: An all-pass filter is any filter with flat amplitude response across all frequencies. The phase response can be anything. Anything, except linear! Link to comment
mansr Posted July 17, 2017 Share Posted July 17, 2017 6 minutes ago, Hifi Bob said: Anything, except linear! It can be that too. Then it would simply be a fixed delay line. Link to comment
fung0 Posted July 17, 2017 Share Posted July 17, 2017 20 hours ago, Fitzcaraldo215 said: Gosh, I bow to your superior wisdom, and your superior semantic skills. Sarcasm does very little to further your argument. Consider editing it out. Fortunately, after years on the Internet, I have become immune... Quote Well, Twitter was certainly built using open internet standards, but do you have their source code? No. That is proprietary. There's certainly some proprietary code running on Twitter's servers. But it's entirely irrelevant. Twitter could open source it tomorrow, and without affecting its business in the least. In any case, it's the open Web standard that enabled Twitter to even be a concept in the first place. Even now, there's negligible proprietary code required on the client side. None at all, to simply view Twitter - I do it all the time, with even JavaScript blocked. Posting undoubtedly requires some JavaScript, but again, that's an open platform. Facebook is a better example, especially when we're discussing MQA. Facebook dominates not because of its brilliant technology, but because it has users locked in to a proprietary communications protocol. There have been suggestions (especially in Europe) that Facebook should be forced to 'open up' that protocols, so other companies could compete on a level footing. There's nothing innovative about those protocols (never was), and they should be standardized. Alas, it's hard to close the barn door once you've allowed the horse to own the barn. Quote Yes, Linux is open. But, IBM and Microsoft invest much more on and receive much greater revenues from their own proprietary stuff than on Linux support. Do you disagree? As it happens, I do disagree. IBM's mainly sells services, with a business model that's built entirely around Linux and open platforms. Some of their code is undoubtedly proprietary, but that's the way Linux is meant to work - you open source the stuff that benefits everyone, keep stuff closed that's specific to your own work. The model works. IBM was once 100% proprietary, now it's largely open - and 100% based on open standards. Microsoft makes most of its revenue these days from the enterprise market. That presumably includes sales of Office, a perniciously closed product, which succeeds only by virtue of lock-in. But otherwise, Microsoft is moving rapidly to embrace open standards. It recently opened all its programming tools, and has contributed big chunks of code to open projects - including Linux. Talk to their enterprise guys, and you'll see the vast shift in mindset that's already well underway. Quote JVC did not give VHS away. Licensing was simply much more favorable to licensees than was Beta. Beta, by the way, was widely considered better in all respects except maximum playing time, but Sony were simply SOBs about the licensing. It's impossible to go into exhaustive detail on each example. VHS was effectively "open" - at the scale that mattered to its users (large corporate manufacturers). If anything, it shows how openness and profit are not mutually exclusive. Quote I do not know the Fraunhoffer story. But, was there no licensing whatsoever required, meaning no revenue stream to them? Weird. OK, just googled them. MP3 is patented and licensed from Fraunhofer, not a free open standard. MP3 encoders were licensed by Fraunhofer (to software and hardware companies) at a very affordable rate. MP3 decoders were allowed to exist without royalties. Even the definitive LAME encoder was allowed to exist as source code, widely compiled by amateurs. Another example of a standard that was sufficiently open to be a standard. The various flavors of MPEG video fall into the same category. Quote CD was not a free, open standard, BTW. The players and discs were manufactured under license from Sony/Philips. Dolby on cassettes was also not free and open. DVD, HD-DVD, Blu-Ray, DTS and Dolby codecs, HDMI, etc. all require licensing. CD is another commercial standard, more than 'open' enough for its users. It probably helped that CD was not exclusively owned by just one company - like SACD, for example. Or Blu-ray, which undoubtedly helped accelerate the shift to streaming as opposed to ownership of video. Dolby was a bit of an oddity - every tape deck had to have it, but nobody I knew used it. Sort of a needless tax on the market. Similar to the one MQA would like to levy. Quote So, you are miffed because MQA chooses not to do business in the completely open standards way that you consider correct and just give their process away. Shame on them. A feeble straw man argument - I never said any of this. You again undercut your own position. I am 'miffed' (if that's the right word) because MQA chooses to sell what could and should be open and, more importantly, standard - if it's worth having at all. MQA asks us to pay for what should be open, and keeps secret what might actually be worth paying for. Quote However, in spite of your philosophy, many other companies have been quite successful while maintaining proprietary protection over their unique technology. In fact, doing so is mandatory to satisfy investors looking for a return on a new idea. That was my point. The 'unique' part may indeed be proprietary. But not the part that's expected to become a roadblock to further development. (Archetypal open licenses like the the GNU GPL 3.0 attempt to encode this principle in legal logic.) It's the old 'one bridge over the river' problem: if you want MP3 to be a standard, you shouldn't expect to keep it as your own exclusive ('closed') property. Of course, fully 'open' standards are ideal, but in most cases 'benign stewardship' suffices. MQA has shown itself to be anything but benign. As I've noted, the market does generally reject attempts at creating tightly proprietary 'standards.' But unfortunately not always. Many abortive attempts at owning the only bridge over the river have been extremely expensive for everyone. We should have learned something by now. crenca 1 Link to comment
Jud Posted July 17, 2017 Share Posted July 17, 2017 IBM is widely believed not to be doing terribly well with the open source and services model for a fair chunk of their business. It’s very possible to succeed, fail, or anything in between with open source. Where you will likely fail unless you achieve market dominance and can dictate is if your standards aren’t interoperable with others’. One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Fitzcaraldo215 Posted July 17, 2017 Share Posted July 17, 2017 1 hour ago, fung0 said: Sarcasm does very little to further your argument. Consider editing it out. Fortunately, after years on the Internet, I have become immune... There's certainly some proprietary code running on Twitter's servers. But it's entirely irrelevant. Twitter could open source it tomorrow, and without affecting its business in the least. In any case, it's the open Web standard that enabled Twitter to even be a concept in the first place. Even now, there's negligible proprietary code required on the client side. None at all, to simply view Twitter - I do it all the time, with even JavaScript blocked. Posting undoubtedly requires some JavaScript, but again, that's an open platform. Facebook is a better example, especially when we're discussing MQA. Facebook dominates not because of its brilliant technology, but because it has users locked in to a proprietary communications protocol. There have been suggestions (especially in Europe) that Facebook should be forced to 'open up' that protocols, so other companies could compete on a level footing. There's nothing innovative about those protocols (never was), and they should be standardized. Alas, it's hard to close the barn door once you've allowed the horse to own the barn. As it happens, I do disagree. IBM's mainly sells services, with a business model that's built entirely around Linux and open platforms. Some of their code is undoubtedly proprietary, but that's the way Linux is meant to work - you open source the stuff that benefits everyone, keep stuff closed that's specific to your own work. The model works. IBM was once 100% proprietary, now it's largely open - and 100% based on open standards. Microsoft makes most of its revenue these days from the enterprise market. That presumably includes sales of Office, a perniciously closed product, which succeeds only by virtue of lock-in. But otherwise, Microsoft is moving rapidly to embrace open standards. It recently opened all its programming tools, and has contributed big chunks of code to open projects - including Linux. Talk to their enterprise guys, and you'll see the vast shift in mindset that's already well underway. It's impossible to go into exhaustive detail on each example. VHS was effectively "open" - at the scale that mattered to its users (large corporate manufacturers). If anything, it shows how openness and profit are not mutually exclusive. MP3 encoders were licensed by Fraunhofer (to software and hardware companies) at a very affordable rate. MP3 decoders were allowed to exist without royalties. Even the definitive LAME encoder was allowed to exist as source code, widely compiled by amateurs. Another example of a standard that was sufficiently open to be a standard. The various flavors of MPEG video fall into the same category. CD is another commercial standard, more than 'open' enough for its users. It probably helped that CD was not exclusively owned by just one company - like SACD, for example. Or Blu-ray, which undoubtedly helped accelerate the shift to streaming as opposed to ownership of video. Dolby was a bit of an oddity - every tape deck had to have it, but nobody I knew used it. Sort of a needless tax on the market. Similar to the one MQA would like to levy. A feeble straw man argument - I never said any of this. You again undercut your own position. I am 'miffed' (if that's the right word) because MQA chooses to sell what could and should be open and, more importantly, standard - if it's worth having at all. MQA asks us to pay for what should be open, and keeps secret what might actually be worth paying for. The 'unique' part may indeed be proprietary. But not the part that's expected to become a roadblock to further development. (Archetypal open licenses like the the GNU GPL 3.0 attempt to encode this principle in legal logic.) It's the old 'one bridge over the river' problem: if you want MP3 to be a standard, you shouldn't expect to keep it as your own exclusive ('closed') property. Of course, fully 'open' standards are ideal, but in most cases 'benign stewardship' suffices. MQA has shown itself to be anything but benign. As I've noted, the market does generally reject attempts at creating tightly proprietary 'standards.' But unfortunately not always. Many abortive attempts at owning the only bridge over the river have been extremely expensive for everyone. We should have learned something by now. I am sure we could quibble for weeks on end about past history and optimum business strategies. But, look at it this way. If you are right that MQA has adopted a course proven to fail in the marketplace, then they have done you a favor. They will fail, and since you don't like their technology anyway, you will be happy. In any case, they have chosen the path that they chose. They will have to live with the consequences whether you or I like their strategy or not. Link to comment
Shadders Posted July 17, 2017 Share Posted July 17, 2017 Hi, Does anyone know what anti aliasing filter was used for CD encoding in the 1980's ?. Was it Bessel, Butterworth, or other, and what was the order and cut off frequency etc ?. Thanks and regards, Shadders. Link to comment
Popular Post Don Hills Posted July 17, 2017 Popular Post Share Posted July 17, 2017 2 hours ago, Shadders said: Hi, Does anyone know what anti aliasing filter was used for CD encoding in the 1980's ?. Was it Bessel, Butterworth, or other, and what was the order and cut off frequency etc ?. Thanks and regards, Shadders. "Other", usually 8th to 12th order elliptical. Typically 35 to 50 dB down at Nyquist. Several companies produced improved performance filters to retrofit to early ADCs, such as the Apogee filters for the Sony PCM-1600 and F1 range. Shadders, esldude, MrMoM and 1 other 4 "People hear what they see." - Doris Day The forum would be a much better place if everyone were less convinced of how right they were. Link to comment
Popular Post Fokus Posted July 18, 2017 Popular Post Share Posted July 18, 2017 Off topic, but page 5 of this document discusses the phase response of the Sony PCM-F1. http://www.audio-focus.com/Townsend/pdf/Why_supertweeters.pdf Incidentally, Meridian's CD replay apodising minimum phase filter (as in the 808.2) has a very similar amplitude and phase response. This really was back to square one! Shadders, esldude and Jud 3 Link to comment
Shadders Posted July 18, 2017 Share Posted July 18, 2017 9 hours ago, Don Hills said: "Other", usually 8th to 12th order elliptical. Typically 35 to 50 dB down at Nyquist. Several companies produced improved performance filters to retrofit to early ADCs, such as the Apogee filters for the Sony PCM-1600 and F1 range. Hi Don, Thanks - much appreciated - will try and simulate the filter. Regards, Shadders. Link to comment
Popular Post fung0 Posted July 18, 2017 Popular Post Share Posted July 18, 2017 13 hours ago, Fitzcaraldo215 said: But, look at it this way. If you are right that MQA has adopted a course proven to fail in the marketplace, then they have done you a favor. They will fail, and since you don't like their technology anyway, you will be happy. As I've tried to make clear, MQA's technology is not my primary concern. What I dislike is the company's attempt to take over a part of our relatively open audio distribution ecosystem, with a proprietary and conspicuously closed 'standard.' Also, based on the historical examples I cited (and others), I do not agree that MQA's chosen course is "proven to fail." Here's what I said in my last post (emphasis added): Quote ..the market does generally reject attempts at creating tightly proprietary 'standards.' But unfortunately not always. Many abortive attempts at owning the only bridge over the river have been extremely expensive for everyone. MQA could take a long time to "fail," and do a great deal of damage along the way. Fortunately, we are under no obligation to sit in pious hope that "the marketplace" will swiftly produce the optimum outcome. If even a few people are persuaded by what they read in this forum to 'wait and see,' to refrain from signing up for early MQA offerings, the impact could be very significant. If even one or two prominent audio journalists are persuaded to reconsider their early enthusiasm for MQA, the impact could be even greater. Maybe MQA audio really is terrific, the greatest thing since Edison. Maybe. But so far, MQA hasn't begun to make a case strong enough to justify ceding part of the music landscape to its new format. Fokus, kumakuma, esldude and 2 others 5 Link to comment
Popular Post Jud Posted July 18, 2017 Popular Post Share Posted July 18, 2017 1 hour ago, fung0 said: MQA could take a long time to "fail," and do a great deal of damage along the way. They could. Currently, they seem to be taking a long time to succeed. Vote with your dollars (as in, the absence of them from MQA). It's a language that gets listened to. esldude, 4est and fung0 3 One never knows, do one? - Fats Waller The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature. Link to comment
Popular Post Fokus Posted July 18, 2017 Popular Post Share Posted July 18, 2017 16 hours ago, Fitzcaraldo215 said: If you are right that MQA has adopted a course proven to fail in the marketplace, then they have done you a favor. ... you will be happy. Quite the contrary. As fung0 already explained, they are on a course of failure, a course that dissipates money and effort. While some may benefit from this in the short term, the music and audio markets as a whole will get even more fragmented, confused, and confusing. There are only victims in the long term. So no, ... me not happy. Ironically, if MQA had been a bit more open from the beginning they would by now have been in a position with a much better chance for long-term success. But no ... they chose to be driven by maximum greed. esldude and fung0 2 Link to comment
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