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jgazal

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Posts posted by jgazal

  4. The (Round) Football Thread

    in Sports Talk

    Posted

    3 hours ago, Torpedo said:

    Brazil played uncoordinated. They're good football players individually, but they don't seem to build pressure and good goal chances. 

    Argentina and Brazil performances were  disappointing. Maybe debut's anxiety? We'll find out soon.

  10. Cavalli Audio Liquid Carbon

    in Headphone Amplification

    Posted · Edited by jgazal

    This was a long time ago, but perhaps it is useful to recollect:

    On 13/09/2010 at 8:52 PM, kevin gilmore said:

    Not exactly.

     

    Fully complementary: a transistor in the top half of a circuit is matched by a transistor of opposite polarity on the bottom half of the circuit.

    Slew rates are identical or close to identical in every section of the amplifier.

     

    Fully differential: input signals with common mode noise with respect to ground are ignored.

    Special care for electrostatic amps, for which the outputs both go up and down with respect to ground for

    common mode noise, but the bias would therefore change for signicant amounts of dc at both inputs.

     

    Symmetry: Everything is active in both directions. The result of fully complementary.

     

    Tubes can be fully differential, lots of circuits exist. Tubes can never be complementary as there is no such

    thing as a p-channel tube. The output circuit of a circlotron can be considered as fully symmetric, but the

    drive circuit is anything but.

     

    Dynalo, dynahi,dynafet,b22 and B24 are all fully complementary, fully differential and fully symmetric.

    Lots of power amps over the years are the same. Very very few dynamic headphone amps do this.

    Mainly due to cost issues.

     

    The electrostatic circuit above is all of the right things. But the required super-symmetry

    causes the input impedance to be way low. Plus a huge amount of parts, lots and lots of heatsinks

    and board area.

     

    kgss, kgsshv, kgbh, T2 and every other stax amp are balanced and have differential inputs, but

    are not symmetric and definitely not complementary either. One of the results is that power supply

    noise and drift are now a significant issue.

    • Like 2

  11. The Headcase Stax thread

    in Headphones

    Posted

    3 hours ago, JimL said:

    OTOH, it appears there are a couple heatsinks in the PS, so maybe they do have a low voltage PS. 

    If you were to design a DAC or a phono pre-amp daughter board to be anchored in the line 4 slot, would you need some kind of high voltage dc to low voltage dc converter?

     

  13. Focal Utopia headphones...with Beryllium driver

    in Headphones

    Posted · Edited by jgazal

    55 minutes ago, mypasswordis said:

    I believe what you're asking can be explained by the Cone of Confusion. (...) You can gain some info in real life based on spectral cues and simply tilting your head to change the ILD and ITD, but with headphones those don't really help. 

    How one can differentiate a source always at 45 azimuth but varying from -90 to +90 degree in elevation?
    I was imagining an algorithm changing the ILD and ITD with a head tracking camera or device input.
    So I need to rephrase my question. 
    Do you believe binaural stereo recordings with dynamic convolution and no crosstalk playback has the same performance of 16 channel with dynamic convolution playback? 
    My criterion would be the number of errors a listener has comparing the the elevation he believes a source is and the true/original n elevation positions the source was recorded.
    Premises are HRTF captured at zero reverberation room and head tracking.
    For instance the 16 channel can be the decoded output of a third order ambisonics.

     

  14. Focal Utopia headphones...with Beryllium driver

    in Headphones

    Posted

    4 hours ago, mypasswordis said:

    (...), audio recording and reproduction is nothing at all like listening to live music, from the start (microphone type and placement to mixing/mastering, etc) to finish (speakers/headphones). Headphones, with the drivers less than an inch from your ear, and with earpads that could be in or on your ear, bypass or change some of that transfer function, like your head and pinna, and have to emulate sound that comes from a point source 3 meters or so away. (...)

    Thank you for posting that explanation.
    Suppose you have your own HRTF measured with two stereo speakers in a low reverberation room (anechoic) and a DSP that not only convolves - without the addition of crosstalk - a ".wav" file recorded with a binaural head microphone, but also equalise your headphones to flat frequency response at your ear canal.
    Do you think the elevation cues - filtered by the binaural head microphone transfer function - only change the listener perception of elevation of a recorded point source (in other words, the listener understand that the source is above or under 0 degree, but the listener doesn't realize the true/original elevation of the recorded point source) or completely ruin the elevation perception (the listener do not hear the source as it were above or under 0 degrees elevation)?
    Now suppose you have a HRTF measured with an sphere arrangement of sixteen speakers (eight at 0 elevation, 4 at +45 degrees and four at -45 degrees) in a low reverberation room (anechoic) and the same DSP above (now there is no crosstalk between the speakers separated by an sagittal plane and you deal with comb filtering of speakers in the same side of such sagittal plane).
    Does this second arrangement improve the listener elevation perception compared to the first arrangement?
    If you think the second arrangement is worst than the first arrangement, how many channels the second arrangement would need in order to achieve the perception performance of the first arrangement?
    I would like to know your opinion.

  15. The Headcase Stax thread

    in Headphones

    Posted

    Thank you for your advice. 

    The input is a balanced dual fet LSK-389 and as far as I know it accepts a single ended signal as long as the negative one is tied to ground. 

    People are used to insert a neutrik adapter which has (again AFAIK) the rca ground tied to both pin 1 and pin 3 inside the connector.

    But there is a paper in which Rane advises that option "a", i.e, the negative input fet of the amplifier is tied to the source ground.

    That's why I am still unsure what to do.  

  16. The Headcase Stax thread

    in Headphones

    Posted

    I'd like to ask for some advise on how to wire a cable to connect a source rca output to an electrostatic amplifier xlr input that have pin one connected to the chassis.

    I have male rca and xlr connectors and coaxial cable.

    I've read that the amplifier negative input fet must be shorted to ground.

    Which of the following two possibilities is correct?

    a - Strand two coaxial cables for each channel. Connect one center conductor between the rca + center pin and the xlr + pin two. Connect the other center conductor between the rca outer shell and the xlr - pin 3. Connect both coaxial cable shields to xlr pin 1 only.

    b - Use only one coaxial for each channel. Connect one center conductor between the rca + center pin and the xlr + pin two. Connect the coaxial cable shield between the rca outer shell and the xlr - pin 3 and short pin 3 to pin 1.

    In both cases, is a resistor between xlr - pin 3 and the rca outer shell (or xlr pin 1) necessary? Which resistance?

    Looking forward to hearing from you.

     

     

    wp_ss_20170129_0001 (2).png

    XLR-to-RCA-580x258 (2).png

  17. Downsizing Speaker Setup

    in Speakers

    Posted

    Quad ESL-57 and (afaik custom modified) Janszen A1.1 horizontal directivity plots.

    Source:

    https://www.princeton.edu/3D3A/Directivity.html

    In the standard Janszen "configuration, the entire area gets the midrange signal, and only half gets treble. In this way, treble dispersion is increased so that it overlaps the midrange dispersion."

    Source:

    http://www.janszenaudio.com/janszen-panel-construction

    The newer active models have digital crossovers.

    I have been looking for an used pair in my country, but they are rare here.

    Quad%20Electroacoustics%20ESL-57%20H%20Front%20Contour%20Plot.png

    JansZen%20Loudspeaker%20zA1.1%20H%20Contour%20Plot.png

  24. World Cup 2014

    in Sports Talk

    Posted

     

    "(...)

    A. The Rights of Celebrities

    Celebrities are entiltled to the same general right of privacy that extends to all individuals. However, the degree to which that right is protected is much narrower for public figures. Articles recounting the details of the daily lives of celebreties generate a much higher level of interest on the part of the public than do similar stories concerning unknown people. As a result, a broad spectrum of information concerning celebrities is transferred from the protective shield of privacy into the realm of the public interest"

    (...)

     

    Celebrities' Rights to Privacy,  Jamie E. Nordhaus, p.289

     

     

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