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onboard passive mid control

Discussion in 'Basses [BG]' started by Daniel Elliott, Mar 2, 2005.


  1. It seems that the passive tone control on most passive basses is a treble rolloff. How hard would it be to do a passive mid control instead? How do you determine the frequency and Q for a passive tone control on a bass?
     
  2. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    This is a tricky thing to do passively. The pickups themselves will have an impact on the characteristics of the system. If you want a mid control, you would be wise to move to an active circuit.
     
  3. If you can do it on an amp, I don't understand why you couldn't do it on a bass. What about the pickup makes it undoable?
     
  4. Juneau

    Juneau

    Jul 15, 2004
    Dallas, TX.
    Dingwall's blueEQube is an upper mid cut passive control.
     
  5. RichSnyder

    RichSnyder Always groove.... Supporting Member

    Jun 19, 2003
    Columbia, Md
    Check out Villex pickups.
     
  6. dadodetres

    dadodetres

    Dec 19, 2004
    URUGUAY
    the controls in your amp are active.

    and also the tone control in a passive bass is only a CUT, you cant boost frerqs. so if you add a mid control it would be a mid cut and not boost
     
  7. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    yup. It has some sort of circuit that allows it to boost AND cut mids. According to Mr Villex, it's not like a passive tone control where the least cut is being applied where the control is at max.
     

  8. GK amps use active eq controls, but the old fender bassman has passive tone controls.

    The bluEQube does what I want but it's an on/off solution. I'd like to be able to adjust the amount of cut with the knob.
     
  9. Juneau

    Juneau

    Jul 15, 2004
    Dallas, TX.
    It does have a knob thats adjustable to the cut. It has an on/off switch as well, but also a knob.
     
  10. If it has a knob, I don't understand why it would need an on/off switch. One way should be flat and the other should be -12dB cut or whatever it's set to.
     
  11. Juneau

    Juneau

    Jul 15, 2004
    Dallas, TX.
    Its "off" position on the knob is set for a specific cut for an auto slap tone. I don't recall what level of cut it is in that position, but Im sure Sheldon could maybe answer that. Basically the off switch is no cut, with it switched on it starts at say -3db and goes up from there, if that makes sense?

    Its possible Sheldon could make you one with exactly what you want too. His user name is Sheldon D., just shoot him a PM. Might have to wait a bit for a response, he is pretty busy at the moment :)
     
  12. lowphatbass

    lowphatbass ****

    Feb 25, 2005
    west coast
    My bluEQube does't have it's own knob, but does change the net effect of the mid control. It is hooked-up to the input of the volume and to the ground..
     
  13. Juneau

    Juneau

    Jul 15, 2004
    Dallas, TX.
    Yeah it used to be a push/pull on the volume, but now it has its own knob and a switch instead. But yeah, Sheldon designed it as far as I know, along with his 4-way position switch for p'ups, so its very possible it could be modified to what you need.
     
  14. lowphatbass

    lowphatbass ****

    Feb 25, 2005
    west coast
    Yea I think you're right..heh, out of curiousity, how is yours wired-in? That sounds sort of similar to the mid option on the OBP-3. Does your bass have two toggles? I have to go back and check-out pic of your Dingy..
     
  15. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    The circuits used in amps have gain circuits that make up for the losses. When you have the controls set midpoint* the entire frequency range has a loss; for your typical Fender type circuit, it's between 22 and 26dB. When you "boost" with one of these controls all you are doing is making the circuit have less loss in that frequency range of the control, not any actual gain. When you cut, it's just more loss of level. The amplifier stage before and/or after the passive tone control makes up for the loss introduced to get your signal levels (at least) back up to where they were before.

    Also, amplifier stages have output impedances that are relatively constant with signal level and frequency which makes it easy to predict how the circuit would work and design so that it's repeatable in the way it works. In a bass, the (passive) pickup is very reactive, ie signal levels and impedances vary with frequency and the volume control is usually wired as a variable series resistance so the impedances seen driving the passive tone network vary a LOT, making it impossible to give a predictable frequency response, so every time you got the mids set right, and you adjusted the volume control the tone would change enough that it would be a PITA to use. Next, passive pickups have low signal outputs, usually under 100mV, so adding in a circuit that drops 26dB means you're now down towards 5mV which is going to make it a real challenge to avoid serious hum or to get a decent signal to noise ratio, especially in a stage environment.
     
  16. That's what I'm after. With the knob all the way up I want it to be flat or no loss, with it all the way down, I want it to have -15db cut. The tone control on passive instruments now is a treble rolloff. Basically doing the same thing at a higher frequency. All I want to do is set the center frequency at 800hz instead of 4k or whatever it usually is. Obviously you would want it to be a dip instead of a shelf type eq as well.
     
  17. I tried to send an email to Villex, but it got bounced. Does anyone have any contact info for them?
     
  18. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Well, you could do a mid-cut with a passive control. Whether or not you like the result would be another story. As for Fender amps, they aren't passive. No amplifier is passive. The tone circuits do use passive components, but you have an active circuit controlling impedance before and after the mid control. You do not have this in a passive bass.
     
  19. I got a response from William Villex! I guess my email made it through afterall. here's what he had to say.

    Hi Daniel,

    *

    Villex pickups are exactly what you describe. Our pickups have huge dynamic range. Bottom end can easy pick C# (check on 12 string Adler bass). Highs are not overwhelming but just give "air". Villex pickups have integrated passive magnetic circuit controlled by 50 K pot. Range is +7 db - 8 db. Frequency deviate between 750 - 820. As you cut it drops to 750 Hz and as you boost it will be around 820. Output is close to active basses. Extremely resistant to hum and buzz. Practically dead quite. I am sure you will love it!

    Respectfully,

    William Villex
     
  20. Juneau

    Juneau

    Jul 15, 2004
    Dallas, TX.

    To be honest, I don't know how its wired lol.