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Bypass box with low-pass filter

Discussion in 'Effects [BG]' started by alexclaber, Aug 26, 2003.


  1. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I'm thinking of building a box that allows my clean signal to run straight through uneffected and gives me two options for when I've got my fx switched in, one fullrange and one with a lowpass filter that mellows out the high end and makes distortions and synths sound more pleasant through my 3-way cabs and less likely to blow the HF protection bulbs.

    The challenge is designed a lowpass filter that will effectively simulate the sound of a bass running through a vintagey-sounding cab (i.e. one without tweeters or separate midrange drivers) and react consistently depending on which effect pedal is driving it.

    Any suggestions?

    Alex
     
  2. Tritone

    Tritone Supporting Member

    Jan 24, 2002
    Santee, America
    Interesting idea. Any reason you couldn't just add an EQ pedal in-line with the synth's? At least that way you'd still have a little flexibility with the signal. If you do wind up making the box, I would suggest putting the attenuator on the return side of the loop. That way, your pedals will still be getting a full range input, and will still react properly, prior to any high frequency attenuation.
     
  3. Jeff Moote

    Jeff Moote Supporting Member

    Oct 11, 2001
    Beamsville, ON, Canada
    You could put a push-pull pot at the return of the loop, and wire it as an on/off switchable tone pot like those in passive basses. That would do it, no?
     
  4. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I don't think that would work because the tone pot on a passive bass interacts with the passive pickups on the bass. Oh, but you can put a passive tone pot after EMG pickups so maybe it would... More investigation required!

    Alex
     
  5. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    Alex, passive tone pots don't interact with the pickups. They bleed off a variable amount of top end signal to ground via a capacitor. When tone pot is at full, tone bleed is at minimum and vice versa.
     
  6. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    OK, I've done a bit of reading around and passive tone controls bleed high end off because the impedance of a capacitor is lower at high freqeuncie so by connecting the capacitor to earth the highs escape through it.

    However, the amount of bleed appears to depend upon the inability of the source (i.e. the pickups) to deliver enough current to compensate for this bleed to ground. Surely active pickups (or in my case) effects pedals have a sufficiently powerful output amplifier to render a standard passive tone control very ineffective?

    Alex