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EQ questions.. i yearn to learn!

Discussion in 'Effects [BG]' started by ::::BASSIST::::, May 15, 2005.

  1. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Alright. I have a fishman pro platinum bass eq/preamp.

    First off, I often hear these terms, but i dont know what they mean:

    -bass shelving?

    -photo-optic compressor? I know what a compressor does, but photo-optic?

    -Low-cut (high-pass) filter

    additionally, what is the relationship b/n the input volume (aka gain?) and master volume on an amp? if i have the input volume set low (say at "3") will that effectively limit how loud my amp will go?

    for example if i set my input volume at 3 on my clarus (so as to get more low-end without distortion) am i losing alot of the 200 watts my amp puts out?

    hope these questions arent too stupid :ninja:
  2. Thurisarz


    Aug 20, 2004
    I want to hear about this too, very interesting little box.
  3. PhilMan99


    Jul 18, 2003
    US, Maryland
    I can help with this much:

    * Photo-optic: Just refers to the type of electronic circuit used for the compression. You can do compression via physical means (speaker/mic, etc.), digital (computerized), photo-optic (light-source and light-controlled resistor), and other methods. [Note: In the fishman, as I recall, the bass is not compressed - just the higher frequencies.]

    * Low-cut: A filter that *cuts* frequencies below a given frequency (e.g. anything below 50Hz). On the Fishman, this is called the "depth" control.

    * Gain vs. volume: No fixed relationship - product dependent. The basic idea is that you want to control the gain INTO a product (Fishman, preamp, combo, stompbox - whatever!) to a) minimize distortion/clipping and b) provide a good strong signal. Volume out is just, well, volume! Generally, with no other distortion effects in your chain, most people probably like a high-gain setting to get a bit of "natural distortion" form the preamp. Fishman instructions (and my combo amp) have you raise gain until the "clip" light occasionally comes on for the "best sound".
  4. Kael


    Dec 26, 2004
    Oklahoma City
    Actually the Fishman compresses the mids and leaves the lows/highs alone. Can't remember freq specs off the top of my head.

    Depth control is cut, so turn it all the way up if you want to get a "flat" setting (ie: to bypass) .

    This is a fun little DI/pre box.
  5. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    A shelving control boosts or cuts one end of the audio spectrum. So a bass shelf might control everything from 20 hz up to 1khz, all at the same time. A treble shelf does the same thing on the high frequencies, like 700hz to 20khz.

    Here's a couple diagrams lifted from Mackie's site. First, a high shelf:


    Then a low shelf:


    Then what a mid control does:


    And here's a link to their site for the text. That should cover it.

    Mackie on EQ

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