Fender input resistor?

Discussion in 'Amps [BG]' started by Grissle, Jan 1, 2014.

  1. Grissle


    May 17, 2009
    I need to change my PA 100's inputs to hi-z. So should I use 68k or 1meg in place of the 22k's.

    Also a non related question. I've read about disconnecting the reverb tank and jumpering the input/output. What is the result in doing this?

    Sorry, forgot the schematic: [​IMG]
  2. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    22KΩ change to 68KΩ. 47KΩ to ground changes to 1MΩ. They're the "standard" values.
  3. Grissle


    May 17, 2009
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  5. a 22k will work fine. Just plug into the lower gain input. When you plug into the high gain input of an amp it puts the two 47- 68ks in parallel anyway....

    edit. Didn't see the 47k to ground.

    I rarely go above 20k on the input resistors on my amps.
  6. Grissle


    May 17, 2009
    FWIW I've read these are low-Z inputs on the PA heads. When I plugged straight in I couldn't get hardly any break-up on it till I went through a preamp first. So I tended to believe it is low-Z?
  7. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Try changing the 47K to something bigger, 470K or 1M. 1M tends to be standard. Try it and see if your signal improves. With that change, the 22K (grid stopper) should be fine. If you can leave the 22K you save some additional work.
  8. Grissle


    May 17, 2009
    Excellent, I'm going to try that first off. thanks.
    I've had tube amps in the past but never with so many configuration and mod options!