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passive tone vs. treble EQ

Discussion in 'Basses [BG]' started by lucas vigor, Sep 7, 2005.

  1. lucas vigor

    lucas vigor Banned

    Sep 2, 2004
    Orange County, Ca,
    I have often felt there is a huge difference in what the tone control does on a passive bass, versus what the treble eq does an active bass.


    On every passive fender bass i have ever played, rolling the tone off seems to completly remove all the treble, resulting in a sound that is soft, muted, and "closed" (sorry, that's the only word I can think of) A sound I highly like.

    Whereas on almost all active basses I have played, I just cannot get the same effect! Rolling off the high EQ only gives me a choice of less or more treble. Much like on my amp. Meaning, there is always some treble (and fret noise) left. This is a big reason why I sold my Sterling, and only use my active Carvin for slapping. Even with the active EQ rolled off completely, the sound is still agressive and "Open".

    Can anyone give me a scientific or logical reason? I asked this same question a few years ago, and was never given a response that made much sense.

    Rolling off the tone on my jazz bass sounds different then rolling off the treble on my active bass.

    Passive rolled off= no string/finger/fret noise at all.

    Active EQ rolled off= less string/finger/fret noise, but not completly gone.

  2. TrooperFarva


    Nov 25, 2004
    New City, NY
    This is a complete guess, but here goes:

    Passive electronics are Cut only. They can't boost anything. So when you turn down the tone knob, the treble is cut.

    Some active electronics are Boost only. So when you turn down the treble knob, there's still treble there, just not as much compared to the Mids and Bass.

    But some active electronics are boost/cut, so perhaps with those, you can eliminate the unwanted fret noises.
  3. KJung

    KJung Supporting Member

    Others can explain the technical differences better than I can. However, many preamps now have active treble/bass (and sometimes mid) controls AND a passive tone control (like on the original Fenders). They also have a bypass switch... so, you can go from very modern active to classic passive on one instrument.... or combine the two... spike up the active treble and then soften it a little by passively rolling back the high end. Very cool... and highly recommended.
  4. lucas vigor

    lucas vigor Banned

    Sep 2, 2004
    Orange County, Ca,
    Thanks guys.....

    I remember seeing a Fender somewhere (Perhaps a victor bailey?) that had the passive tone added...strikes me that it would be EXTREMELY useful to have that option on all active basses!

    If my Sterling had come with a passive treble cut, I never would have sold it!

    it was an awesome bass, looks (Orange tangerine sunburst) great slap tone, killer neck, excellent construction, and totally unseable when I wanted to practice with my Aretha Franklin "best of" CD!!

    I got rid of it!


    TrooperFarva, Does it look like someone spit in my hamburger?

    Loved that movie!
  5. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    using an active eq treble control cuts a variable amount at a specific frequency / bandwidth

    using a passive tone control rolls off a progressively higher amount above a certain frequency.
  6. A9X


    Dec 27, 2003
    Sinny, Oztraya
    TBer DavePlaysBass did this simulation of a JB network with 250k pots and a 47nF (0.047) tone cap, ie a fairly typical passive tone control network.


    Look at the magenta curve: that's with the tone pot fully open. Now look at the green one: that's with the tone control fully closed. As both curves begin to drop as they move to the right, any frequencies above this point are attenuated, or reduced. So as you 'close' the tone control, the more upper harmonics are reduced and the frequency where that reduction starts gets lower as the pot turns more counterclockwise.

    If you use a larger cap, both curves will be shifted to the left, a smaller cap, to the right.

    An active tone control works differently. Instead of reducing the level of all the harmonics above a certain point like the passive network, it boosts and cuts around a certain frequency for a certain bandwidth around that frequency.


    Midrange controls have a response like this, as do some bass and treble controls, depending on what the designer chooses.

    There are some variations on the active filter curves possible, eg shelving. These are used in some applications for bass and treble controls.


    As a side note, the 'active' curves are the same as you will find in the EQ controls of your amps and combos.

  7. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    Like Dharmabass said: the two sound different because they produce different types of curves.

    A passive tone control is a lowpass filter: it will for example, be 0 dB (that is, no effect) at one point in the frequency spectrum, then -6 dB an octave above that, -12 dB two octaves above the first point, -18 dB three octaves above the first point, -24 dB four octaves above the first point, up to -infinty dB, or zero output, as the frequency approaches infinity. Changing the tone control basically changes where the rolloff point starts.

    An active treble control is typically a high shelving filter. Using it to cut treble, it behaves as follows: it will for example, be 0 dB (that is, no effect) at one point in the frequency spectrum, and slope down to -<some number> dB at a point one or two octaves higher. The -<some number> is set by the tone control position; the frequency points, however, are fixed.

    The result is what you are hearing. The passive puts a "full clamp" on all frequencies significantly above the cutoff point, and the cutoff point can be turned down fairly low. The active shelf maintains that same -dB out to infinity in the treble direction, and no more.

    Hope that explains the graphs a bit (rather than making things worse!).
    Dexter_Bass likes this.
  8. lucas vigor

    lucas vigor Banned

    Sep 2, 2004
    Orange County, Ca,
    Thanks Guys!
  9. Fuzzbass

    Fuzzbass P5 with overdrive Gold Supporting Member

    Cool explanation. I do think that many active treble controls are bandpass rather than shelving, though: instead of all frequencies above, say, 4kHz, there's a bump centered at that point.
  10. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    I think you're right. Both are used, and neither gives the ever-increasing cut with increasing frequency that a passive provides. I think I saw one a day or two ago which combines a "bump" with a shelf.

    Noll has some interesting ones. Here's their basic 3-band fixed frequency:
    Note how the bass has shelf plus bump, but the treble has bump only on boost, so that hiss is not accentuated, but shelf with only a slight bump on cut.

    Another interesting idea used by John East on the Retro preamps is that (IIRC) the cut is at a lower frequency than the boost, which I would imagine would be to make it sound more "choked," similar to a passive, when cut.