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Thread: PRaT - please explain

  1. #61
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Hi Anthony
    As I recall you asked me to do a square wave frequency sweep for linearity, Square waves as readers might or might not know, are the furthest
    one can go from reality as representing music , its as alien to our ability of hearing, as you can possibly get.

    To show this on the left in the first image is a graphical display of a piece of music, and on the right a square wave generated at 20 hz

    Testing with music, Yes always valid, as it reveals the relationship of the musician and equipment to preserve the discussion topic - timing
    in direct relationship with our hearing ability

    As example the next image shows a square wave at 1000 hz and 17000, can the reader see any difference from 20 hz to 17000 hz ?
    yet these same range of frequencies are seen contained in the graphical display of music.

    Your assertion is as I understand that i test with a dual trace oscilloscope using a frequency generator providing a square wave to see any deviation with a square wave generated and then following
    is that right ?

    To further explain how alien graphical displays are, can anyone identify the artists playing in the music... ? and no cheating looking up the title Crawl Space
    and ask yourself can you see the interplay between musicians, the acoustic of the drum sound, the reverberation of the trumpet and is the topic timing revealed
    that makes the music so special to hear ?
    Attached Images Attached Images

  2. #62
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Some clever side stepping there Chris,
    A simple test using a dual scope would give an indication of whether the equipment in question was at least capable of reproducing the most basic of test parameters, ie; a square wave comparison of the signal before; and after the piece of equipment, would indicate any frequency discrepancies, phase shift, and any non linear amplitude activity at diffrent volume positions etc.
    This would be a good starting point.
    Quote Originally Posted by Light Dependant Resistor View Post
    Hi Anthony
    As I recall you asked me to do a square wave frequency sweep for linearity, Square waves as readers might or might not know, are the furthest
    one can go from reality as representing music , its as alien to our ability of hearing, as you can possibly get.

    To show this on the left in the first image is a graphical display of a piece of music, and on the right a square wave generated at 20 hz

    Testing with music, Yes always valid, as it reveals the relationship of the musician and equipment to preserve the discussion topic - timing
    in direct relationship with our hearing ability

    As example the next image shows a square wave at 1000 hz and 17000, can the reader see any difference from 20 hz to 17000 hz ?
    yet these same range of frequencies are seen contained in the graphical display of music.

    Your assertion is as I understand that i test with a dual trace oscilloscope using a frequency generator providing a square wave to see any deviation with a square wave generated and then following
    is that right ?

    To further explain how alien graphical displays are, can anyone identify the artists playing in the music... ? and no cheating looking up the title Crawl Space
    and ask yourself can you see the interplay between musicians, the acoustic of the drum sound, the reverberation of the trumpet and is the topic timing revealed
    that makes the music so special to hear ?
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  3. #63
    Join Date: Sep 2011

    Location: Weymouth, Dorset

    Posts: 46
    I'm Dave.

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    Quote Originally Posted by Pharos View Post
    That sequence would need some scrutiny IMO.
    Hi Dennis, you're absolutely right: reading my post back I can see that it made no sense. What I was trying to say was that record player and the streamer seem to my ears to be better at timing than the CD player. I guess that's no big revelation.

  4. #64
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    Quote Originally Posted by Light Dependant Resistor View Post
    Hi Anthony
    As I recall you asked me to do a square wave frequency sweep for linearity, Square waves as readers might or might not know, are the furthest
    one can go from reality as representing music , its as alien to our ability of hearing, as you can possibly get.

    To show this on the left in the first image is a graphical display of a piece of music, and on the right a square wave generated at 20 hz

    Testing with music, Yes always valid, as it reveals the relationship of the musician and equipment to preserve the discussion topic - timing
    in direct relationship with our hearing ability

    As example the next image shows a square wave at 1000 hz and 17000, can the reader see any difference from 20 hz to 17000 hz ?
    yet these same range of frequencies are seen contained in the graphical display of music.

    Your assertion is as I understand that i test with a dual trace oscilloscope using a frequency generator providing a square wave to see any deviation with a square wave generated and then following
    is that right ?

    To further explain how alien graphical displays are, can anyone identify the artists playing in the music... ? and no cheating looking up the title Crawl Space
    and ask yourself can you see the interplay between musicians, the acoustic of the drum sound, the reverberation of the trumpet and is the topic timing revealed
    that makes the music so special to hear ?
    Ignoring your wording, which is obscure, looking at waveforms in a comparative way cannot reveal anything, but a square wave should be reproduced accurately; it has known amplitudes of all harmonics, and the phase of each of these has to be preserved in order for the wave to be accurately square.

    No we don't listen to square waves, but they are a very good model with which to measure failings in several parameters.

  5. #65
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

    Default

    Indeed!
    The main concern i have, and i would guess anyone contemplating the use of a paticular product is; if the product in question is being promoted on its superior accuracy, in comparison with a conventional potentiometer, then as a starting point, it should at least test as well, using the method described, if on the other hand; the designer of said product is promoting said design soley on its perceived superior musicality, ie; the way it performs in conjunction within a specific system, then i would argue that that's not the same as promoting a product on its known superior accuracy.
    Quote Originally Posted by Pharos View Post
    Ignoring your wording, which is obscure, looking at waveforms in a comparative way cannot reveal anything, but a square wave should be reproduced accurately; it has known amplitudes of all harmonics, and the phase of each of these has to be preserved in order for the wave to be accurately square.

    No we don't listen to square waves, but they are a very good model with which to measure failings in several parameters.
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  6. #66
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Quote Originally Posted by anthonyTD View Post
    Indeed!
    The main concern i have, and i would guess anyone contemplating the use of a paticular product is; if the product in question is being promoted on its superior accuracy, in comparison with a conventional potentiometer, then as a starting point, it should at least test as well, using the method described, if on the other hand; the designer of said product is promoting said design soley on its perceived superior musicality, ie; the way it performs in conjunction within a specific system, then i would argue that that's not the same as promoting a product on its known superior accuracy.
    It suits all audio systems where power amp sensitivity is 1.5 v for full output or preferably less, and fixed resistance loading is below 20k. Its circuit form to partnering equipment is a L pad

    Subjectively using music, it has been compared to conventional potentiometers here: https://www.stereo.net.au/forums/top...eo-coffee-diy/

    "I was actually cynical about the whole LDR idea. I did try a stepped attenuator but it wasn't any better than my ALPS it was cleaner but it was also harsh. A bit disappointing.

    That's when I decided to give LDR's a go. Wow!

    I have had some nice valve amps and I have to say that the LDR is an amazing alternative if you running a solid state. I would imagine it would nice with a valve amp as well.

    I have heard an autoformer/transformer but it didn't have the magic."

  7. #67
    Join Date: Feb 2008

    Location: South Wales

    Posts: 9,151
    I'm NotTakingLifeTooSeriouslyTheseDays.

    Default

    Quote Originally Posted by Light Dependant Resistor View Post
    It suits all audio systems where power amp sensitivity is 1.5 v for full output or preferably less, and fixed resistance loading is below 20k. Its circuit form to partnering equipment is a L pad

    Subjectively using music, it has been compared to conventional potentiometers here: https://www.stereo.net.au/forums/top...eo-coffee-diy/

    "I was actually cynical about the whole LDR idea. I did try a stepped attenuator but it wasn't any better than my ALPS it was cleaner but it was also harsh. A bit disappointing.

    That's when I decided to give LDR's a go. Wow!

    I have had some nice valve amps and I have to say that the LDR is an amazing alternative if you running a solid state. I would imagine it would nice with a valve amp as well.

    I have heard an autoformer/transformer but it didn't have the magic."
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    Its now a conspiracy theory to believe that the Immune system is capable of doing the job it was designed to do.
    A fish is only as healthy as the water its swimming in ! [Dr Robert Young]


    www.tubedistinctions.co.uk

    Matthew 5:10

  8. #68
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

    Default

    Quote Originally Posted by anthonyTD View Post
    Indeed!
    The main concern i have, and i would guess anyone contemplating the use of a paticular product is; if the product in question is being promoted on its superior accuracy, in comparison with a conventional potentiometer, then as a starting point, it should at least test as well, using the method described, if on the other hand; the designer of said product is promoting said design soley on its perceived superior musicality, ie; the way it performs in conjunction within a specific system, then i would argue that that's not the same as promoting a product on its known superior accuracy.
    In essence my view on the subjectivist supposition of matching, is that it is based on amelioration of errors by countering and offsetting one with another; this may give a sound more acceptable or pleasing, but does not increase accuracy.

  9. #69
    Join Date: Jan 2008

    Location: Gerrards Cross

    Posts: 2,991
    I'm Tony.

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    The ideal harmonic content observer would be a spectral FFT, a lot of the modern digital scopes have a half respectable one fitted these days (1m points) though ideally a real time spectral analyzer is most useful for this.

    I have always found that passive pre's 'ring like a bell' at 4 and 10Khz with a square waveform (which after all is just made up from various sine waves and their harmonic components) which means an awful lot of overshoot on the top half of the wave form.

    Happy to do some experiments for you Tony so we can illustrate this.


    I have attached some screen shots from our R&D scope, first is of a rather good 10Mhz world clock we have been working on for a new customer project.
    This has all of the basic meas horizontally below the wave form.

    Below this is the spectral content on this particular clock measured up to 200Mhz this give an indication of how HN is present in a square wave form of this type, granted we are talking lower orders of magnitude but the principle is the same and in some cases the lower frequency SW can produce more detrimental harmonic noise due to their poss poor formation on some crappy PC dac and not a respectable function generator.

    The next image is the basic wave form showing the eye pattern and RJ jitter histogram plus on the LeCroy oscilloscopes we have a X-stream eye which is an extrapolated software model of the actual real time data stream.

    Final image shows a full serial decode of the word clock data transmission including trend/bath-tub/PJ/RJ/DJ etc.







    Coherent Systems
    Real high end sound with musicality not hifi

  10. #70
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    One of the hardest things to do, and which has become evident to me, is to accept the volatility and vulnerability of what we hold to be true.
    The adhesion to ideas and concepts which are not valid or true may provide a comfort zone, but inevitably they separate us from reality, stifle or dealing with it, and sabotage our own growth and development.

    There is IME a great freedom facilitated when we stop hanging on to dogmas, and I welcome any dissent because it to have my beliefs challenged helps me grow.

    Blake; "A man convinced against hi will is of the same opinion still"

    Dylan; "The naked truth is still taboo wherever it can be seen."

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