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  1. #1
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    Power cord and IC affecting sound..

    Decided to start a new thread...with a quote from mtry..

    Quote Originally Posted by mtrycraft
    Great. Keep us updated. We are here to learn as well.
    I detailed to Bruno in a jpeg, the mechanism surrounding how a PC cord and IC can affect the sound of a system. Also, how to isolate it and measure it.

    The equation of the error voltage presented to the amp input is:

    Verror=(Ip * fp2 * K1 * K2) / Rloop

    Verror is the error voltage which appears at the amplifier input.
    Ip is the current within the power cord, entire haversine spectra.
    fp is the frequency of the haversine harmonic considered.
    K1 is the coupling factor between the PC and the ground loop formed by the amp, source, and the power cords.
    K2 is the coupling factor between the ground path of the input, and the input signal.
    Rloop is the total loop resistance formed by the pc ground, IC shield, and source ground.

    As is evident by inspection, the error voltage is proportional to the square of the frequency component, the current of each harmonic in the line draw, the geometry of the PC/ground loop interaction, the geometry of the amp ans source internal grounding scheme, and inverse to the ground loop resistance.

    So, clearly, a relationship between all the components is there...for me, that is not an issue..The real question is...given adequate test design and care, can it be reliably measured....and, once measured, is it of sufficient magnitude to affect the sound?

    As is also evident from the picture, the mechanism I detail has absolutely nothing to do with the miles and miles of wire back to the power company..That argument is entirely without merit for the schematic I depict. (oh, forgot to label the top dot in the picture...that is the ground at the wall socket.

    Also note...although I draw a hard ground for the source, it could be a simple capacitive coupling..one which provides sufficient signal path for the higher frequencies of the haversine..

    What I did not include in this presentation is the bleed-back of high frequency audio signal into the line...the bulk parameters of the supply is insufficient to block the coupling.

    Cheers, John
    Attached Thumbnails Attached Thumbnails Power cord and IC affecting sound..-scan078-march-31-2004.jpg  

  2. #2
    Forum Regular Bill L's Avatar
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    Talking Anyone get that? Anyone?

    Ears: Just add one to each side of head and enjoy! Where'd I put that beer anyway?
    Attached Images Attached Images  

  3. #3
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    OK, I'll bite

    Interesting analysis. It will be even more interesting to see what effect there is in changing a power cord, which parameters of the cable has the most effect, and how this effect is passed on to the output terminal to affect the audio signal. And or what effects the IC will contribute by itself or in combination with the power cord.

    Going back in time, any news of your skin effect measurements?

    Did you get the binaural discrimination document?
    mtrycrafts

  4. #4
    Forum Regular Rockwell's Avatar
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    Quote Originally Posted by Bill L
    Ears: Just add one to each side of head and enjoy! Where'd I put that beer anyway?

    Don't forget the brain in the middle.
    "You two are a regular ol' Three Musketeers."

  5. #5
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    You listen to music with your brain? Please explain to how you do this!
    Remember, different isn't always better, but it is different.
    Keep things as simple as possible, but not too simple.
    Let your ears decide for you!

  6. #6
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    Quote Originally Posted by bturk667
    You listen to music with your brain? Please explain to how you do this!

    Your brain is what makes you aware of what it is beyond a digital impulse from the ears. And, it is the one that confuses many by false perceptions too. Actually the center of operations for everything.
    mtrycrafts

  7. #7
    Forum Regular Rockwell's Avatar
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    Quote Originally Posted by bturk667
    You listen to music with your brain? Please explain to how you do this!
    Your ears are just sensors. The brain is...well the brain and processes the information. Just like your mouse is not the "brains" of a computer, it is just an entry point for information. As amazing as the brain is, it is easily fooled.
    "You two are a regular ol' Three Musketeers."

  8. #8
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    digital ?

    Quote Originally Posted by mtrycraft
    Your brain is what makes you aware of what it is beyond a digital impulse from the ears. And, it is the one that confuses many by false perceptions too. Actually the center of operations for everything.
    and here I was thinking (brain in action ?) that it was analog coming in

  9. #9
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    Even if a power surge filter is different from a PC, such devices may affect the output at the signal level:

    http://hem.bredband.net/b113928/Surgefilter.htm

    In addition, it has been tested on a separate equipment with similar results.

    The filter introduce audible noise similar to "static" sound.

    T

  10. #10
    Forum Regular Bill L's Avatar
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    Talking

    Quote Originally Posted by Rockwell
    Don't forget the brain in the middle.
    That's what the beer is for! Relax. Kick back. etc.
    Last edited by Bill L; 04-02-2004 at 12:59 PM.

  11. #11
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    From the way I understand your equation, V(error) is a spurious noise signal appearing at the amplifier input as the result of coupling between the PC and the signal ground forming an unintended ground loop. This noise appears as the square of the frequencies in Ip which for the base frequency is 60*60= 3.6khz and for a first harmonic 120*120= 14.4 khz. All higher harmonics are well beyond the audible range. The difference in performance of one PC versus another is related then to the coupling factors K1 and K2. Do I understand you to mean when you say ["K2 is the coupling factor between the ground path of the input, and the input signal.
    "] that the term input here is meant to be the AC power input?

    Do you have any measured or calculated range of K factors for different PCs? Doesn't K1 and K2 to a large extent depend on the internal topology of wire and component layout in the amplifier and source, and the physical arrangement of the interconnect wire and the PC external to the components? So doesn't this signal appear in effect as the residual hum and noise? But then this does not come as any surprise as the admonition of keeping power cords away from signal cables has been given from time immemorial. External decoupling then could better be accomplished by an additional shield on the signal cable than on the PC because unlike the PC, heat dissipation is not a consideration. Artificial means to shield power cords is not only a violation of UL unless designed in by the manufacturer and UL listed such as in the case of MC or BX cable or THWN/THHN run in flexible metal conduit such as greenfield but it can cause cable overheating and the risk of fire or shock.

    It is clear that the neutral conductor referred in NEC as "the grounded electrode" is current carrying and is grounded usually at the service entrance to the premesis. The defeating of the safety ground if one is provided in the manufacturer's power cord is not only dangerous and illegal, it is useless because under normal conditions ground current does not flow through that conductor. Similarly installing "ferrite rings" on the ground conductor is therefore equally useless as it is dangerous. Installing ferrite rings on the phase and neutral conductors may marginally increase the overall power input circuit inductance but is probably all but useless as well.

  12. #12
    Forum Regular Rockwell's Avatar
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    Quote Originally Posted by Bill L
    That's what the beer is for! Relax. Kick back. Get that stick outta ... nevermind.
    You don't have to tell me what beer is for
    "You two are a regular ol' Three Musketeers."

  13. #13
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    John, I also assume that R1, R2, and R3 are really Z1,Z2, and Z3. Wouldn't Z1 and Z2 be in the megaohm range normally? What about Z3 at 3.6 and 14.4 Khz? These should be fairly low. What are typical values?

  14. #14
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    Quote Originally Posted by skeptic
    John, I also assume that R1, R2, and R3 are really Z1,Z2, and Z3. Wouldn't Z1 and Z2 be in the megaohm range normally? What about Z3 at 3.6 and 14.4 Khz? These should be fairly low. What are typical values?
    They are indeed impedances..For this analysis, I considered only resistance. And they should be in the sub ohm ranges.

    A loop of conductor will develop a voltage that is proportional to the rate of change of the flux captured by the loop, dB/dt... For a sinusoidal flux change, the rate of change of flux is the derivative of the flux...as the frequency goes up, the slew rate, ie, flux rate of change, goes up, directly proportional to the frequency. So, I used the variable K as including the time derivative, to keep the equations simple.

    The inclusion of f2 was not meant to represent the frequency being transferred, but a factor for the strength of the coupled signal.

    Sorry for not including the simplification of terms in my explanation..

    An example:

    Say, a 100 mV signal input causes 100 watts at the speaker.

    The supply will draw haversine current, 60 hz, 180 hz, 300 hz, 420 hz..540 hz..660 hz

    Assume 2 amp line draw..60 hz component..1 amp 180 hz comp, 1/2 amp 300 hz.

    Now...goto the final equation...

    Assume that at 60 hz, the 2 amps will cause say, 1 millivolt of error signal..

    At 180 hz, 1 amp, three times the frequency means 9 times the coupling (freq squared), so the 180 hz component will be (half the current times 9 times the coupling).

    So, the 180 hz error signal will be 4.5 millivolts.

    At 300 hz, 1/4 the current, but 25 times the coupling.. 6.25 millivolts.

    420...49/8=6.125 millivolts..

    Using these 4 harmonic terms, adding their peaks..(don't forget how a haversine is made from the frequency components), 17.75 millivolts of error signal, with a 100 millivolt signal..17% peak waveform distortion..and it's haversine derivative stuff..

    Now, these numbers were pulled out of the hat, as I assumed 1 millivolt error at 60 hz..

    The error at 60 could easily be just 100 microvolts...try measuring that level in an amplifier delivering 100 watts to a load....not exactly an easy task.

    But, that level of coupling would add 1.7% errors, in the prev example..

    Now....this has been only a haversine discussion...those nefarious loops also exist in the supply section of all amps..So what keeps the 5 Khz amp output signals from feeding into the PC loop?

    And, that frequency will couple 6,800 times more than 60 hz..so even 10 mA of audio injected into the line cord will be an issue...

    What would be more important IMHO, is that bleedback of that type in the audio band would not necessarily be waveform distortion per se, but phase shift...and most spectrum analyzers do not see phase shift, but measure waveform distortions.

    If phase shift occurs as a result of this, then the phase shift would be amplitude dependent...and, how would we interpret that effect in a binaural soundstage??? What words would an "audiophile" use to describe that effect??? Beats me...

    Mtry....skin analysis and testing: I recently moved, and all my stuff is in boxes until I can finish sheetrock, rug, and windows in the attic, then I can start to build my audio test setup in the basement. Skin effect takes a back seat to life...

    And yes, I did get that document...I am amazed that even one or two people could hear 2 microsecond deviations..

    Bill L: Yes, at least two people understood it..

    Cheers, John

  15. #15
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    Quote Originally Posted by skeptic
    that the term input here is meant to be the AC power input?

    Do you have any measured or calculated range of K factors for different PCs? Doesn't K1 and K2 to a large extent depend on the internal topology of wire and component layout in the amplifier and source, and the physical arrangement of the interconnect wire and the PC external to the components? So doesn't this signal appear in effect as the residual hum and noise?

    External decoupling then could better be accomplished by an additional shield on the signal cable than on the PC because unlike the PC, heat dissipation is not a consideration. Artificial means to shield power cords is not only a violation of UL unless designed in by the manufacturer and UL listed such as in the case of MC or BX cable or THWN/THHN run in flexible metal conduit such as greenfield but it can cause cable overheating and the risk of fire or shock.

    It is clear that the neutral conductor referred in NEC as "the grounded electrode" is current carrying and is grounded usually at the service entrance to the premesis. The defeating of the safety ground if one is provided in the manufacturer's power cord is not only dangerous and illegal, it is useless because under normal conditions ground current does not flow through that conductor. Similarly installing "ferrite rings" on the ground conductor is therefore equally useless as it is dangerous. Installing ferrite rings on the phase and neutral conductors may marginally increase the overall power input circuit inductance but is probably all but useless as well.
    Input is the audio input.

    I have no measured K values.

    K1 is absolutely dependent on the line cord geometry, external wire dressing, and amp internal power circuitry dressing. K2 is totally dependent on the internal ground loop configuration within the source box and the amp box...how the first loop currents are routed affects the coupling to the input circuitry.

    I kept your warnings about pc mods intact, as they are worth repeating..

    Shielding will be absolutely worthless, as any shield will NOT eliminate the external flux..copper is useless to remove this coupling. Mu metal will enhance the field strength around the pc..the only possibility would be to use mu metal to divert the flux around the rest of the ground loop, so none gets trapped in the loop.

    The only way to reduce the PC field generation is to coaxially run hot and neutral..This will completely eliminate external fields for the pc, but is entirely against all code..running the wires in a conduit won't work because there is no cylindrical symmetry for external field cancellation.

    Same with amp internals....even a star ground is worthless for this.

    The signal is a result of amp draw, which varies with signal..if you could draw dc off the supply cap, the xfmr draw would produce the signal at the amp input.

    Perhaps using a load to pull dc current off both caps, and monitoring the output terminals with no input signal? That would show haversine coupling constants, forcing that error term to be visible at the outputs, without the confounding issue of the input signal..

  16. #16
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    And yes, I did get that document...I am amazed that even one or two people could hear 2 microsecond deviations..
    Could you please provide more information. Reference, please. Is this document available for me to view?

    wmax@linaeum.com

    Thank you.

    -Chris

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    mtrycrafts: I would greatly appreciate a copy of the binaural time sensitivity paper, to which you have referred.

    wmax@linaeum.com

    Thank you.

    -Chris

  18. #18
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    Quote Originally Posted by WmAx
    mtrycrafts: I would greatly appreciate a copy of the binaural time sensitivity paper, to which you have referred.

    wmax@linaeum.com

    Thank you.

    -Chris
    Early christmas
    mtrycrafts

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    I would also like to know how to get this article

    T

  20. #20
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    Quote Originally Posted by Thomas_A
    I would also like to know how to get this article

    T
    email me Large file though, 2meg or more. can you handle it?
    mtrycrafts

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    Quote Originally Posted by mtrycraft
    Early christmas
    Thank you.

    -Chris

  22. #22
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    Thanks Mtry,

    just some comments/questions. The 0.2 Ás discrimination point is not between frequencies but "between ears", thus binaural. The audible limit for phase deviation for pulses with respect to frequency and time is in the 1-2 ms region, according to the litterature. The implication of this article for cables should be minimal, except where cables cause differential deviations in phase between channels (?)

    T

  23. #23
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    Quote Originally Posted by Thomas_A
    just some comments/questions. The 0.2 Ás discrimination point is not between frequencies but "between ears", thus binaural. The audible limit for phase deviation for pulses with respect to frequency and time is in the 1-2 ms region, according to the litterature. The implication of this article for cables should be minimal, except where cables cause differential deviations in phase between channels (?)
    T
    Nope. The implications of this article w/r to cables can be HUGE....

    The first experiment shows that jitter can be used to extend the human capability for lateralization of the image. If you look at the upper curve, the one with no jitter, you see that at about 1.2 Khz, the human threshold climbs rapidly to 15 uSec, with a minimum threshold of about 5 uSec.

    But when jitter is introduced, the lateralization threshold drops down to 1.5 uSec at 2 khz, extended out to 8 Khz, where the data ends for this experiment.

    For a complex musical waveform, if a human is keying on a 2Khz signal, trying to identify the location in space, the rest of the audio signal may be introducing a jitter, or some other phenom similar to it, to aid in lateralization..

    If the amp/cable/speaker combo is unable to maintain the 2Khz slews to less than 1.5 uSec consistancy, will it's reaction to the complex waveform into a complex load be entirely jitter free?

    This article definitely raises some interesting questions. It certainly may impact what and how we test cables, looking for a smoking gun..

    If you look at the Goertz waveforms, note that the timebase for the scope pics is 10uSec...and the 12Khz waveform rises in 10 uSec.

    Approximately 6.6 TIMES what this paper identifies as measureable when jitter is in the stimulus...

    Oh, don't forget...the human ear has a different compression/rarefaction response, measured in the half millisecond range, if memory serves me correctly..

    Is it possible that the BASS signal in the music is causing jitter of the ear response to the 500 hz to 5 Khz, thereby introducing a mechanism whereby humans can distinguish 1.5 uSec temporal shifts???

    Cheers, John

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    Quote Originally Posted by jneutron
    Nope. The implications of this article w/r to cables can be HUGE....

    The first experiment shows that jitter can be used to extend the human capability for lateralization of the image. If you look at the upper curve, the one with no jitter, you see that at about 1.2 Khz, the human threshold climbs rapidly to 15 uSec, with a minimum threshold of about 5 uSec.

    But when jitter is introduced, the lateralization threshold drops down to 1.5 uSec at 2 khz, extended out to 8 Khz, where the data ends for this experiment.

    For a complex musical waveform, if a human is keying on a 2Khz signal, trying to identify the location in space, the rest of the audio signal may be introducing a jitter, or some other phenom similar to it, to aid in lateralization..

    If the amp/cable/speaker combo is unable to maintain the 2Khz slews to less than 1.5 uSec consistancy, will it's reaction to the complex waveform into a complex load be entirely jitter free?

    This article definitely raises some interesting questions. It certainly may impact what and how we test cables, looking for a smoking gun..

    If you look at the Goertz waveforms, note that the timebase for the scope pics is 10uSec...and the 12Khz waveform rises in 10 uSec.

    Approximately 6.6 TIMES what this paper identifies as measureable when jitter is in the stimulus...

    Oh, don't forget...the human ear has a different compression/rarefaction response, measured in the half millisecond range, if memory serves me correctly..

    Is it possible that the BASS signal in the music is causing jitter of the ear response to the 500 hz to 5 Khz, thereby introducing a mechanism whereby humans can distinguish 1.5 uSec temporal shifts???

    Cheers, John

    I am still confused. The ability to hear phase/time difference is higher with a jittered signal. How can that translate into importance of cables if the phase/time difference is identical between right and left channel?

    T

  25. #25
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    Quote Originally Posted by Thomas_A
    I am still confused. The ability to hear phase/time difference is higher with a jittered signal. How can that translate into importance of cables if the phase/time difference is identical between right and left channel?
    T
    Why do you assume that the difference is identical for both channels?

    Can you be sure the amplifier damping factor and slew rate capabilities are constant through all four quadrants of operation? And that the inductance/capacitance of speaker cables does not affect that? Don't forget, left and right channels do not necessarily occupy the same quadrant at the same time..

    Given the possibility that large acoustic signals can jitter the sound enough to allow 1.5 uSec discrimination, we now are faced with the possibility that 1.5 uSec waveform sloppyness as a result of amp/wire/speaker combinations is audible..

    That is over 600 Khz..Way the H##L over anything we can possibly hear..

    So, if we can discriminate 1.5 uSec shifts, why do we limit testing to 20Khz?

    As I said, the article raises some very important questions.

    Cheers, John

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