Massively overbuilt 45 headphone amp.

Discussion in 'DIY' started by johnjen, Aug 4, 2018.

  1. Cspirou

    Cspirou They call me Sparky

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    Never really seen the grounded leg filtered with a choke before. Seems to offer some isolation between PSU ground and signal ground.
     
  2. johnjen

    johnjen Friend

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    hahahahahahahahahahahahahahaha
    Ya gotta use a texas drawl when saying iiiirrrrrrnnnn for the full effect , such as shoot'n iiiirrrrnnn.

    JJ:)
     
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  3. MrTeaRex

    MrTeaRex His head's not fat, he's my brother!

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    Nobody down here sounds like they're pushing out a log while pronouncing the word iron.
     
  4. johnjen

    johnjen Friend

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    That LCLCL grounding scheme allows for improved common mode rejection according to the Lundahl tech sheets, and a few designers who are involved in this build.

    JJ
     
    Last edited: Sep 23, 2018
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  5. famish99

    famish99 Friend

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    I don't, but I kinda wish I did now.
     
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  6. johnjen

    johnjen Friend

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    So we are working on a few design issues, and I have taken the time to tear a portion of the amp apart to re-route/move/reconfigure sections of the amp.

    Here are the latest drawings of the PS innerd's and placement on the board.

    45 amp layout-14.pdf
    45 PSU-2.pdf

    JJ
     

    Attached Files:

  7. johnjen

    johnjen Friend

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    I have re-wired about 50% of the power supply (all the filament wiring and the diode bridge) and about 80% of the analog section with the remaining 20% due when parts arrive.

    I've moved/shuffled/nudged xfmrs around and have a 4.5 x 4.5 area to handle all the filament power requirements.
    And I can accommodate either ac or dc filament power for the 45 tubes, in that same space.

    And the xfmr count is up from our previous 14, to 17 or 19 if we use dc power for the 45 filaments.


    IMG_1926.jpg

    IMG_1931.jpg

    The yellow cables are the twisted shielded filament runs that will originate in the lower right hand corner.

    JJ
     
    Last edited: Oct 6, 2018
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  8. johnjen

    johnjen Friend

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    Tonight I finished the re-wire job and await a couple of resistorators.
    We have devised a solution to the high line voltage and the next step will be to dial in the important voltages and bias currents.

    JJ
     
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  9. johnjen

    johnjen Friend

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    So here is a pic of the solution to my 'high' line voltage.
    A hammond 169J, a 750VA multi tapped secondary, line voltage isolation xfmr.

    IMG_2003.jpg

    JJ
     

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