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Thread: Help with Masco MA50 tone stack

  1. #1
    Junior Member
    Join Date
    Oct 2006

    Help with Masco MA50 tone stack

    How can this tone stack be altered for more bottom?
    The amp is a Masco MA50 that has-
    grid leak input pentode first stage
    volume control
    paralleled twin triode
    tone stack as shown (original)
    balanced paraphase PI
    6l6 x 4 cathode biased with plate V around 400.
    The amp has new filter caps and .1 mfd coupling caps.

    See link if the pic fails.

    Jim R
    Attached Thumbnails Attached Thumbnails masco_tone_stack.jpg  

  2. #2
    Old Timer
    Join Date
    Jun 2006
    I'd perhaps start by weaking the value of the 25K mid resistor (45), then maybe try a larger cap at 24?

  3. #3
    Senior Member
    Join Date
    Mar 2007
    Philadelphia suburbs
    "More Bottom" could mean one of two things:

    1.) Lower the cutoff frequency
    2.) Increase the volume of the Bass making it through the tone stack.

    I doubt you are referring to #1. The .1uF coupling cap should be plently large to gett all the low frequencies that you need.

    To increase the amount of bass making it through the tone stack you should probably look at reducing the value of the 270k resistor going into the bass tone knob. That 270k resistor makes a voltage divider with the pot. Reducing the value of the 270k should increase the bass volume a bit.

    You can also add some series resistance to the treble to change the balance of treble to bass to give the illusion of "more" bottom.

  4. #4
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Lansing, Michigan, USA
    Amen, not enough bottom is not very different from too much top. ALL passive tone controls can do is cut, and there is a limit to how much they can reduce their cutting - that is to say they can;t boost anything. SO reducing the rest of the spectrum while leaving hte bottom alone results in the same overall effect.
    Education is what you're left with after you have forgotten what you have learned.

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