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Is there a 3-way switch for: passive mag or piezo w/pre or both..into one jack ?

Discussion in 'Pickups & Electronics [BG]' started by jibreel, Oct 20, 2009.


  1. jibreel

    jibreel

    Apr 12, 2005
    Seattle
    Greetings,

    I am installing a Villex passive magnetic pickup in my Carvin AC-50 which already has piezo with the Carvin pre. I do not want to install a new pre which could blend them.

    So... is there a 3-way switch that I could install that would let me choose from mag pickup only or piezo pickup only or both? And could this send the signal to one jack?

    Any wiring diagrams?

    Thanks
     
  2. ebassotti

    ebassotti

    Aug 2, 2007
    Have you considered replacing the mono jack with a stereo one, with the piezo preamp output on the tip, the magnetic pickup on the ring, and shared ground on the sleeve? That would give you flexibility for external blending or even stereo/bi-amping, and would be fully reversible in case it should turn out you don't want it after all.

    Just a thought.
     
  3. jibreel

    jibreel

    Apr 12, 2005
    Seattle
    Thanks for the idea.

    Since I will have seperate volume and tone controls for both the mag and the piezo on the bass, it would be nice to have the three switch option for easier control. But I am open to all suggestions !
     
  4. Are both pickups (piezo and magnetic) feeding the preamp?
    It wouldn't be a good idea to use one with the preamp and one passive, as you would be combining high and low impedances.
     
  5. fullrangebass

    fullrangebass

    May 7, 2005
    Europe
    IIRC there are DI boxes that allow for 2 basses to be plugged in. I am not aware if they allow a mix between the two, but for sure they will be able to offer a choice of the two signals offered by the bass
     
  6. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    you can not mix a passive magnetic with a passive piezo, they're like oil and water electronically (one's an inductor, one's a capacitor). you also will have little luck trying to mix a passive mag with an active anything; all you'd hear would be the active part.

    either the magnetic gets its own path down a stereo cable to its own amp, or it gets preamped and then mixed with an also-preamped piezo. for combining, those are your choices.
     
  7. jibreel

    jibreel

    Apr 12, 2005
    Seattle
    Thanks all. Looks like I will just run the mag pup and the piezo into seperate channels on my amp.
     
  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    actual separate amp channels with separate volumes, or multiple inputs into the same channel? because the latter wouldn't work either.
     
  9. HogieWan

    HogieWan

    Feb 4, 2008
    Lafayette, LA
    just put a simple impedance matching buffer on the passive output and then blend. It's the same type of circuit you get at the front of a stompbox or the front of an amp.
     
  10. jibreel

    jibreel

    Apr 12, 2005
    Seattle
    My main Acoustic Image amp has two seperate channels. So I would just run the signals seperately into the two channels. I will have on board volume and tone controls for each pickup. The original Carvin V/T/T premap for the piezo pickup and the Villex will have Volume and his mid-control along with his passive rotary tone booster.
     
  11. HogieWan

    HogieWan

    Feb 4, 2008
    Lafayette, LA
    Another option might be tape-wound strings. They are rounds with the nylon wrapping. They sound very much like rounds through magnetic pickups (obviously not the same, but close, even with a pick), but they are very thumpy over a piezo because of the softer material touching the bridge. This may give you a good mix of tones. LaBella tapes can be had relatively cheap at carvin.com
     
  12. jibreel

    jibreel

    Apr 12, 2005
    Seattle
  13. bassbenj

    bassbenj

    Aug 11, 2009
    I'd like to add a magnetic pickup to my AC50 as well. It's the ONE thing that bass really needs. Mixing the two is a nightmare. I have a guitar with magnetic and piezo pickups and I did the stereo jack thing. I use a stereo cable and I built a small box that takes a stereo cable in and has two mono jacks out. You just put two ordinary guitar cords into those and run to two inputs (or two amps...which can sound amazing!).

    Another thing to try would be a passive mixer. Just insert a 20k or so resistor in series with each output (piezo and magnetic) and then tie the two far ends together as the output point to the amp. This will reduce the overall signal level but should mix without a problem. A series switch that selectively turns off (opens up) each output can add control. So long as you can live with the reduced signal this may work.

    I'd like to know what you do because I want to mod my AC 50 with a magnetic pup too!
     
  14. zorf

    zorf

    Dec 27, 2007
    you can not mix a passive magnetic with a passive piezo, they're like oil and water electronically (one's an inductor, one's a capacitor). you also will have little luck trying to mix a passive mag with an active anything; all you'd hear would be the active part.


    I respectfully disagree.

    I like just blending two together to a simple mono out.

    One blend pot and one volume.

    The mag is alway much hotter, but you learn where the taper is on the pot.

    For me, simpler is better.
     
  15. bassbenj

    bassbenj

    Aug 11, 2009
    As Einstein said: "Things should be as simple as possible, but not simpler!"

    You are correct that one can hear the piezo fine, but it does not work well on bass. I have a simple passive magnetic-piezo setup I built for a resonator guitar and it's fine. A 1 meg pot mixes in the Piezo.

    But here's the Oil and Water story. A piezo is a VERY high impedance device. If you feed it into a low impedance (low here meaning 100k like a typical amp input) it loses all it's low frequency output. On a guitar that doesn't much matter. On a bass it's critical. Hence bass piezos usually have some kind of active preamp with a very high impedance input (1 meg is minimum and 10 meg is better) where you use the OUTPUT from that preamp to mix with the magnetic pickup output.

    In the case of a Carvin AC 50 the piezo pre is already there. I'm guessing that a 25k resistor in series with each output and tie together at the amp would mix them fine.
     
  16. Justyn

    Justyn Supporting Member

    Jun 24, 2002
    Richmond, VA
    Not to hijack the thread, but my bass has a passive pickup mated to a buffered piezo with a vol-vol-tone setup and I get a sharp dip in volume when I start to back off the magnetic volume. It (the volume) comes back, but could this be caused by the dreaded oil/water combo of un-preamped magnetic and buffered piezo setup?

    Thanks,
    J.
     

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