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About Negative Feedback

Discussion in 'Tech Notes' started by FractalAudio, Jan 5, 2014.

  1. jefferski

    jefferski
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    Thanks for the advice on rather than turning up the Damping, turn down the Master. You described it perfectly - I find that sometimes the breakup on a Fender model can be a bit harsh and have gotten in the habit of compensating by turning up Damping, which does clean it up nicely but you're right - it becomes kind of sterile. Will make a note to try the Master next time.
     
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  2. reclavea

    reclavea
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    Cliff,

    Thanks a bunch for your generosity and time to deliver these in depth information on the science of all this!

    This surely sparks enlightenment and appreciation for those of us who crave for deeper knowledge and understanding!

    Definitely MUST KNOW information when sculpting our own sound!

    Kudos again ....much appreciated!



    ......someone should wiki!
     
    ALE likes this.
  3. Jul

    Jul
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    Inspired

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    Electronics and Electrical theory contain the most abstract concepts I've ever encountered in my life. My hat's off to all of you that get it. I remember being exposed to AC circuits in college where they presented the material in terms of " i " ...." i " being the square root of -1. Think about it. Subsequently I happened to fail that class and swore I'd never venture into that realm ever again.
     
  4. GM Arts

    GM Arts
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    And strangely .... the " i " you refer to is used to generate Fractal patterns! I think we've come full circle :lol
     
  5. FractalAudio

    FractalAudio
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    Electrical Engineers use 'j' for sqrt(-1) because we use 'i' for current.

    Imaginary numbers are no big deal. It's just a convenient way to represent certain physical quantities that require two values to describe them. In electronics a sine wave is a fundamental concept since all real signals can be broken down into a sum of sine waves (Fourier theory). A sine wave has a magnitude and phase. It can also be described using a complex number which is the sum of a real value and an imaginary value. Using a complex number makes calculations easier since the mathematical rules on complex numbers are straightforward. For example if we add two sine waves of the same frequency we get a sine wave. If we try to do this using the magnitude and phase it's cumbersome, i.e. a1 * sin(wt + theta_1) + a2 * sin(wt + theta_2) = ?. With complex numbers it would simply be (a1 + jb1) + (a2 + jb2) = a1 + a2 + j(b1 + b2).
     
  6. rodzimguitar68

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    anybody got a cold compress and a shot of whiskey? I need to lay down after this....
     
  7. Sixstring

    Sixstring
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    Wow... I should have gone further in my electronics studies. Hey Cliff, it's really cool to see you posting more often :encouragement:, nice to know your accessible and not completely chained to your work... Thanks very much!
     
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  8. smcrosby

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    :lol now you are taking me back to my freshman E.E. classes at Rutgers. :)
     
  9. Funeral

    Funeral
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    Now that is some knowledge I needed. Thanks for the details.
     
  10. DukeOfPrunes

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    Cliff, do you frequently encounter zeroes and poles in these types of computations and if so, does it have any effect of the overall stability of the system.

    Really just curiosity on my part, since I encountered these in my one and only complex analysis course 30 yrs ago...

    Cheers and hope the knee will be back online soon...gotta log that Carr amp to the MIMIC shop...
     
  11. Stadanko

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    Hi Cliff,

    I have forgotten a lot from my calculus and linear algebra days. My question is on linearity. I always seem to get it in my head that the term "linear" ends up meaning that we are dealing with non exponential equations. So x^x would not exist in a linear equation. Is linearity more complex than that? If so I certainly don't in expect you to teach a class here! Most people in non mathematical world, terms think of linear as a straight line or a rate of change which is simple and straight forward. Like if events are in chronological order then we say they are linear in nature. I know if I could clarify linearity in relation to this topic, I would be well "clued in" a bit more..:D

    Thanks
    Frank
     
  12. chris

    chris
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    I just read the OP for the 10th time since it was posted a year ago. I finally understand!!
     
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  13. shatteredsquare

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    since the Dual Rec Modern mode actual amp has no negative feedback, I've read that the presence control in modern mode is actually part of the preamp, like a separate top end filter after the preamp. Is the model in the Axe Fx the same as that? If you turn the recto modern Sag to zero and the model presence control turns to a hi cut, is it the same filter?

    I read on the firmware notes that the recto models are now an "exact digital recreation" so i would assume so, but I also read in a few firmwares before that some amps got "corrections" to various parameters or component values that were either off, or needed to be updated.

    but i also read that you got some crazy different values from a bunch of different Recto heads, some with different pot values and tapers and such. do you know what year the modeled rectos 1 and 2 are in the latest FW?

    it's good to know all these details about how the controls interact based on the amp design, it's much easier to dial in tones than just blind experimentation. without knowing it's like trying to track vocals not knowing what threshold attack release and ratio do. if you know it's like playing with legos. just build stuff.
     
  14. Mike Ruby

    Mike Ruby
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    Very informative post! It makes me feel like I'm taking the right path for our project with the AXlll. Am I wrong to assume that negative feedback produces odd order harmonic distortion versus even order distortion in most circuits?
     

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