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Parametric Frequency Selector? What does this do exactly?

Discussion in 'Pickups & Electronics [BG]' started by MistaMarko, Mar 11, 2009.

  1. MistaMarko

    MistaMarko Supporting Member

    Feb 3, 2006
    Hey guys,

    I recently purchased a Conklin GTBD-7 7-String bass to mess around with. Regardless, there are so many knobs compared to my old five string, and I'm just trying to get a firm understanding of what they do.

    I have 6 knobs and a small 3-way switch.

    I'm assuming the knobs (correct me if I'm wrong) are:

    1) Volume
    2) Bass cut/boost
    3) Mid cut/boost
    4) Treble cut/boost
    5) Pick-up selector blend-tone knob
    6) This switch doesn't have a smooth rotate..has 4 settings that offer 4 very different tones..not too sure EXACTLY what this is doing or what it is called

    7) This little three-way switch. Everytime I change it, I don't notice any difference at all really..or maybe I don't know what to listen for. I'm assuming this is the Parametric Frequency Selector after reading the manual?

    Anyone want to help me out with this? (as well as any of the other knobs too..)

    Thanks guys..:bag:

  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Post a link to the manual, I'll see if I can make sense of it. Are you familiar with para EQ in general and just not sure of its app. in this case, or are you not familiar with para EQ in general yet?

  3. My guess is, that small 3 way switch is a frequency selector switch for the midrange knob. Assuming that's what it is, it will have no impact unless the midrange knob is moved off of center (flat). So (again assuming your description is correct), the switch selects different center frequencies for the midrange control, probably ranging from the low mids to the high mids. The mid knob then increases or decreases the mid frequency distribution around the center frequency point selected by the switch.

    So, turn up the mid control and move the switch to different settings. It should be very noticable. These types of variable mid controls can be quite useful (i.e., cutting upper mids for less clank, or boosting lower mids to fatten up the tone when you are favoring just the bridge pickup, etc.).
  4. Found this in a review:

    .....The bass sports a single volume control with a pickup blend pot, then things get complex. Tone controls are bass, mid and treble cut/boost, with a four-position (plus "off") brightness switch, a three position (250/400/800Hz) mid freq EQ center select and a pull-up 30 Hz boost on the bass EQ pot......

    So, that four position knob type switch seems to be a treble boost circuit. My description of the mid switch seems correct.
  5. MistaMarko

    MistaMarko Supporting Member

    Feb 3, 2006
    Thanks man..I appreciate your help. I understand the 4-way switch but still seem to have a difficult time grasping the 3-way switch:

    So the options are 250Hz, 400Hz, and 800Hz.

    So let's say I flick the switch to 250Hz. Then I start using the mid cut/boost knob. Ideally, does that make the knob go from 0-250Hz? Then I switch it to 400Hz then it goes from 250-400Hz, and so and so forth? Or is that number the minimum Hz you can boost?...or if both of these are completely incorrect, if I had it at 250Hz would it make that number the center...so then 150-350Hz or something?

    By control you mean the knob, right? And by "turn-up" you mean turn the mid cut/boost knob all the way up?
  6. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Cut and boost refer to the level of the signal, not the frequency. How much that selected frequency range is turned up or down in "volume".
  7. Per Bongo's post, think of the knob as 'volume' and the switch as 'frequency'.

    Most midrange controls (fixed or semi-parametric) have a frequency distribution that looks a bit like that 'normal curve' you learned about in school if you ever took a statistics class. The 'center frequency point' set by the switch is the 'peak of the curve' (i.e., it's the frequency that is most impacted by the volume knob... either cutting or boosting). However, there is a distribution around that curve, so that frequencies above and below the center point (e.g., 250) are also impacted to a lesser degree, resulting in a smooth, musical cut or boost of a distribution of frequencies around that center point. So your 150-350 example is pretty accurate. It's probably wider than that, but that's the basic point. Just remember that the farther you get from the center point, the less the frequencies are boosted or cut, due to the slope of the distribution around the center point.

    The difference between a 'semi-parametric EQ' like on your bass and most amps, and a 'full paramentric EQ' is that with a full parametric, you have another control that can actually spread or tighten the distribution of frequencies impacted around that center frequency point (from a very thin 'notch' to control feedback to a very wide spread to greatly fatten your tone, etc.). This frequency distribution is called the 'Q', and is typically set rather wide on a semi-parametric (i.e., fixed Q) EQ.

    Hope that makes sense. You will hear it clearly if you crank that mid knob (mid volume) and then go through the three switch settings.

  8. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
  9. Stealth


    Feb 5, 2008
    Zagreb, Croatia
    Basically, if you switch to 250 Hz, you boost or cut that plus the surrounding frequencies. Shift to 400 Hz, and you boost or cut that. Same for all other freq locks. Moral of the story is - the frequency selector shows you which frequency will be boosted or cut the most - but it also affects anything around it.

    Example given:

    +6 dB boost at the center frequency of about 55 Hz. If you switched to, say, 400 Hz, the peak would be right above the 400 Hz frequency.

    Edit: Damn. Beaten to it.
  10. A picture is worth a thousand words though:)
  11. MistaMarko

    MistaMarko Supporting Member

    Feb 3, 2006
    Wow guys..I really appreciate your time to explain it all.

    I must say that is some pretty freakin' complicated stuff...I just hope I can utilize it correctly in a band setting and actually understand how to use it properly.

    So JUST TO MAKE SURE, this is what I have so far...(this should be right..)

    The selector simply highlights what frequency I'm going to be boosting or cutting. Switch to 250, then I turn the volume down in the frequency spectrum for that specific level. Sort of like a mixing board.

    So if I'm not messing with the 400Hz or the 800Hz and I'm cutting/boosting the 250Hz range...what is the understood "volume" of the other 2 frequencies that I DON'T have selected? Do they just stay flat? (I would assume so..)


  12. A little EQ goes a long way usually, so you might not cut or boost at all with the mid... just use your ears there.

    Again, if you look at the frequency distribution graph posted above, you will see that the typical 'Q' distribution of frequencies will contain a wide range of frequencies. So, if you boost or cut at 400hz, you will PRIMARILY be boosting or cutting mostly at 400, BUT there will be a slight boost or cut all the way down to 250 and below and all the way up to 800 and above, since those frequencies are contained in the overall distribution of frequencies being boosted or cut. However, you (and your audience) will hear the boost at 400, for example, sound 'lower' than the boost at 800, since the peak of that frequency distribution (peak meaning the frequency that is boosted the most as you turn up the mid control) is at 400.

    It will become clear to you as you sit and mess with it. Set the rest of your controls to the flat setting, and set your blend in the center position. Then, pluck a lower open string (A or E). With your other hand, play around with boosting and cutting the mid knob at the three different settings. You will hear that boosting the mids at 250 will add 'fat' and 'chest thump' to your tone, and cutting at 800 a bit will take away 'clack and gank' from your tone (that upper mid harshness). Boosting a lot at 400 will add what many describe as 'nasal honk', and cutting a bit in that area will give you the classic 'slap scoop' type tone.

    Hope that helps. Remember, it's not that complicated. Setting the switch at 400 and leaving it alone will result in that mid control being voiced similarly to most 'fixed' mid controls on on-board preamps, that seem to typically be centered in that 400hz region.

  13. Human Bass

    Human Bass

    Aug 26, 2005
    Complicated?! Try a filter-based EQ :D

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