9100 9200 One Wire Mod!!!

Discussion in 'The Workbench' started by The Tone Doctor, Feb 12, 2019.

  1. The Tone Doctor

    The Tone Doctor New Member

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    Greetings to all. Thought of share a tip for the 9100 9200 and 50/50 100/100 power amp users out there. For those that like to tweak an mod...here's an easy one. Open the bottom cover and simply clip the white wire from each output transformer (4 ohm tap) and solder it to the lug of the 8 ohm tap instead. So now the 4 ohm lug on the output transformer is disconnected... and the 8 ohm lug now has the original purple wire plus the newly added white wire soldered together... Boom!!! Instant improvement in low end girth and overall freq response via tuning the NFB circuit .


    The Tone Doctor Custom Audio
    Houston TX
     
  2. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    the EL34 have 8 & 16 ohm out...

    upload_2019-2-12_0-23-12.png
     
  3. The Tone Doctor

    The Tone Doctor New Member

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    4 ohm lug is present internally.
     
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  4. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    could you post an image?
     
  5. The Tone Doctor

    The Tone Doctor New Member

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    Ill try. The output transformer has 3 wires. White is 4 ohm. Purple is 8 ohm. Yellow is 16 ohm.
     
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  6. The Tone Doctor

    The Tone Doctor New Member

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    Its also visible on the schematics
     
  7. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I just want to see the finished wiring, so, when I pull my amp apart, I can compare & know exactly what you did...

    I don't have a schem', but, I can easily compare mine to the schem'. That won't show me what yours looks like...
     
  8. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    How about sound samples before and after?

    Dogs, he is moving the feedback from the 4 ohm tap to the 8 ohm tap.
     
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  9. gretsch58

    gretsch58 New Member

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    Okay, you're saying the white wire is just the NFB wire?
     
  10. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Yes, if the white wire is connected to the 4 ohm OT tap then it is the line for feedback to the PI, according to the schematics.
     

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