EQ curve questions for effects & amps

Discussion in 'Effects, Pedals, Strings & Things' started by gregrjones, Jan 16, 2015.

  1. gregrjones

    gregrjones Member

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    With a graphic EQ, of course if you were to simply raise every band to the max, it is basically equivalent to raising the volume knob because the curve is still flat.

    But my question is on either an amp or effects pedal with bass, mids and treble knobs, if I max all three out, am I essentially doing the same thing? Or is each knob typically centered on a frequency without enough overlap to be raising ALL frequencies?

    For instance, if say a bass know were centered on 100 hz and the mids at 1.1k (nevermind whether or not those frequency numbers are typical), while the 100 hz frequency would be boosted, there would be a dip between that frequency and 1.1k.
     
  2. Blues Lyne

    Blues Lyne Member

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    Unfortunately, it depends on how the tone stack is implemented. On an amp like a BF Fender, the controls are interactive and don't react at all like a graphic EQ might. Changing the treble can also change the curve for the bass, changing the bass can have an effect on the mids and so on. At most settings there is somewhat of a mid scoop in the tone stack itself. The flattest response from the tone stack is with mids close to max treble all the way down and bass at somewhere between off and 1. There are other places in the amp where highs and lows are shaped, so even though the tone stack setting may be producing a mid scooped EQ curve the overall tone of the amp could be very mid forward.

    All tone knobs at 10 gives you a similar EQ curve as when they are at 5, but the mid scoop will be shifted lower, say centered at 300hz with tone controls maxed and 550hz with them at 5. Marshall's tone stacks are similar but not identical. While this type is probably the most common type with tube amps, other amps (including some tube amps) have different tone stacks with different responses.

    Download the Duncan Tone Stack Calculator here http://www.duncanamps.com/tsc/download.html . It can be a big help in seeing what is going on with some tone stacks. It has Fender, Vox, Marshall and Big Muff among others. Keep in mind that it only shows what is happening in the tone stack.

    With pedals, it just depends on how they implement the EQ. Some are active and some are similar to the passive tone stacks in Fenders or Marshalls.
     
    Last edited: Jan 16, 2015
  3. KevinFinn

    KevinFinn Member

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    I wish the Duncan thing was available for Mac.
     
  4. Chris McKinley

    Chris McKinley Member

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    Also, gregrjones, simply raising all sliders of a graphic EQ to max does NOT result in a flat EQ curve. Depending on the brand of EQ, the frequency of each slider would be boosted by whatever the maximum gain value is, plus all those frequencies above and below each peak frequency, with the relative drop-off being a function of what is called the 'Q' value for each slider.
     
  5. gregrjones

    gregrjones Member

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    Chris, I figured that might be the case in some situations if the q is not wide enough between frequencies
     
  6. StompBoxBlues

    StompBoxBlues Member

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    Excellent reply! Also good to mention, on some pedals (not all, again it depends on how they implement the EQ) where you just have bass and treble control, you can still somewhat raise the mids by turning down bass and treble to a degree and raising the whole volume.
     

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