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Split grid stopper?

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  • Split grid stopper?

    If I want to use a grid stopper between triode stages as something of a voltage divider (following a volume pot) to attenuate signal, BUT I'm concerned about treble roll-off (it needs to be a somewhat high value), is it possible to split the resistive value into two daisy chained resistors and use a treble bypass cap over one so that there is a differential between total attenuation and treble/high mids attenuation? In other words, the entire signal will be attenuated to a particular degree by the final resistor right on the socket, but the previous resistor will attenuate the lower frequencies more as there will be a bypass cap of maybe 400-500 pf over the top of it. MEanwhile, I don't think it would impede the grid path to ground. So, I guess I'm wondering if there is any potential problem here? Any thoughts?

  • #2
    At least, I should mention *I think* it might act as a voltage divider, can't it? Seems as though in conjunction with the volume pot wiper, it will create a variable divider.... ????

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    • #3
      Yes, at high frequencies I think it will act as a voltage divider. The idea itself should be work, give it a go. As long as the resistive path between the grid and ground doesn't rise above about 2M (eg when vol pot is on full), it should be ok.
      Last edited by pdf64; 10-15-2010, 10:05 PM. Reason: Revised due to mis-reading OP
      My band:- http://www.youtube.com/user/RedwingBand

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      • #4
        If you bypass part of the grid stopper resistance, the bypassed portion won't be doing any grid-stopping. The volume control itself is already a variable divider.
        -tb

        "If you're the only person I irritate with my choice of words today I'll be surprised" Chuck H.

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        • #5
          Anything after the grid leak will only interact with miller capacitance right? What preamp tube are you using? What is the miller capacitance of it? You can then calculate Fc=1/2piRC. To find the frequency at which your resistance values will cut highs, substitute your grid leak with R and the miller capacitance with C and voila. Adobe isn't working for me right now and I don't know the MC for a 12ax7 off the bat.

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