Converting the AD797 MC Phono Pre to a MM Phono Pre - A Mixed Design.

Discussion in 'Turntables' started by USMC Spike, Jan 1, 2019.

  1. wyn palmer

    wyn palmer Well-Known Member

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    Just go for it. You KNOW you can do it!!!
     

     

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  2. wyn palmer

    wyn palmer Well-Known Member

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    2p5mvMMRIAA.PNG
    C2, C1 and Cr0R3 as close tolerance as you can get and try to match ch-ch.
    All Rs 1%. Otherwise, as in the AD797MCPRE.
     
  3. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    Thank you:bowdown:
     
  4. wyn palmer

    wyn palmer Well-Known Member

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    Is there a chicken emoji anywhere?:D
     
  5. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    More lazy than afraid:dunno:
     
  6. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    ..."getting to know you...."

    A brain dump would be much faster and more efficient,
    but that is still a ways off.

    Wyn, while you are here...

    ...Why when I changed the value of the small resistor in the
    feedback path made no difference in the output from yesterdays post.

    Then I'm off again to buy the wife's cars.

    The stealerships do this to me. :whip:


    because I don't :bowdown:


    and accept their fees, add on, etc.

    I looking for an :angel:

    but I get these:deal:

    my jaw
    :eek2:

    they're words:blah::blah::blah:

    you said you would treat me:king:

    but you treat me :naughty:

    :wtf:

    I say, Hasta La Vista....arsch loch.

    So as our Native Home Boy sings LINK

    The post wouldn't be complete with out my kids favorite
    emoticon....
    :banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana::banana:

    USMC_Spike :rockon:

    Post Script - When the dust settles, and I bring home
    the wife's new vehicle and see her smile, I'll work the sin again.
     
    Last edited: Jan 10, 2019

     

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  7. USMC Spike

    USMC Spike AK Subscriber Subscriber

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  8. wyn palmer

    wyn palmer Well-Known Member

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    Good. But, as a general rule, you don't need to worry about noise outside the audio band- except that it's good to simulate it to check to see if there are any pathological issues that could be exposed by it. Sometimes resonances and other issues are apparent looking at the noise and are less so when looking at the frequency response- for instance a near oscillating current mirror or current source would not necessarily appear in the frequency response but would appear in the noise.
     
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  9. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    woops, not yet. Where do I enter to make it a 5.5 VRMS normialized input?
    The other sim, let me find it and put it below here. I've got about 30mins I think.
     
  10. wyn palmer

    wyn palmer Well-Known Member

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    583
    Which small resistor in which simulation? Sometimes you just have to look closely enough. If we're looking for responses within a few 10s of mdB sometimes you need to zoom in.
     
  11. wyn palmer

    wyn palmer Well-Known Member

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    583
    Remember the ac sim does not care about the amplitude of the input- except that it simplifies the interpretation if you normalize the input to the desired input level so that you get the desired output level.
    The 5.5mv rms refers to the AC scaled input (c. -45dBv) which is the input of the preamp you asked for. For this preamp the noise and gain is lower than for the one intended for a 2.5mv rms sensitivity.
    So, in one case (your request) 5.5mv rms @1kHz produces 1v rms at the output, and in the "new" case 2.5mv rms produces the same 1v rms.
     

     

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  12. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    Here is where I am I only see V(outmixed1) I cannot find the V(onoise) either in schematic or the plot.
    I went back to the original mixedriaanew schematic and plot.
    upload_2019-1-10_13-3-59.png
     
  13. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    Then If I want to do a sine sweep, do I just input a 1Vrms @1kHz ?

    Then how do I add the Aweighting to it. That might be the second paragraph
    or the last paragraph but haven't worked my way down to that yet.
     
  14. wyn palmer

    wyn palmer Well-Known Member

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    583
    If you look at your noise plot you will see that it's labelled v(onoise). Remember, the frequency response and noise simulations are different animals.
     
  15. wyn palmer

    wyn palmer Well-Known Member

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    Are you talking about a transient analysis? There is a way to do a chirp in transient- is that what you're asking?
    If so, there are changes that need to be made and I don't have time to walk you through it, and I'm not sure why you would wish to do that when all you have are behavioral models for the opamps etc. and not device level models.
     
  16. wyn palmer

    wyn palmer Well-Known Member

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    Follow the instructions in the earlier post. It's still the same noise simulation that doesn't care about the input level, but with the network added after the amp output.
     

     

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  17. wyn palmer

    wyn palmer Well-Known Member

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    V(onoise) does NOT refer to a circuit node. It refers to the output noise (onoise) voltage. It's measured at the node you specified in the simulation command.
     
  18. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    I think I got it correctly operating now:

    upload_2019-1-10_13-17-57.png upload_2019-1-10_13-18-43.png
     
  19. wyn palmer

    wyn palmer Well-Known Member

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    583
  20. USMC Spike

    USMC Spike AK Subscriber Subscriber

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    No, not yet. I'll have to figure that out. I'll go back and see if I can't figure
    out how to insert the Aweighting network.

    Great, first LTSpice XVII wants to update itself including all 6,000 + files.

    Son of More Joy.
     

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