Question, single channel AA964 build

Discussion in 'Amp Tech Center' started by Diverted, Oct 11, 2019.

  1. Diverted

    Diverted Tele-Meister

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    Hi all, a few quick questions about building a Vibrolux Reverb AA964, single channel (see pic).

    Question 1: I assume I should remove the 220K isolation resistor circled in blue? The mixing resistor on the unused normal channel is shown removed in the red circle.

    Question 2: Looks like two cathodes in the normal and tremolo channel are shared (green circles) . Assuming I should change the cathode resistor to 1.5K (original at 820) to account for it not being shared by two cathodes?

    Question 3: Anything else I should do as I pull the normal channel out?

    Thanks!

    Ted

    Screen Shot 2019-10-11 at 8.jpg
     
  2. peteb

    peteb Friend of Leo's

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    Per Robrob and his blackvibe amp, you will want both the isolating and mixing resistances in place otherwise the signal going into the LTPI is too large.
     
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  3. schmee

    schmee Poster Extraordinaire

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    The resistor across the first preamp cathode cap that is 820 should be changed to 1500. Shown here off p in 8 of the first 7025
    [​IMG]
     
  4. Diverted

    Diverted Tele-Meister

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    Check on the 1.5k cathode resistor. Thank you!


    And Peteb, thanks for the Blackverb tip. I hadn’t seen that before and it’s a big help. I’m using both reverb and tremolo and deleting the normal channel so I take it I would just put one 220k out of the second gain stage into the PI? Thank you!
     
  5. schmee

    schmee Poster Extraordinaire

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    Yes , I believe so.
     
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