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Piezo buffer build !

Discussion in 'Pickups & Electronics [BG]' started by giuseppecaporus, Mar 11, 2014.

  1. giuseppecaporus


    Dec 19, 2013
  2. RobbieK


    Jun 14, 2003
    Firstly, you'll need buffers for both the piezo and the magnetic pickup(s). The diagram in that link looks like it won't work for a piezo, but may be OK for your magnetic pickup(s). A typical piezo pickup needs 5meg and up as a load impedence. Generally this is done with a fet. Try googling "fet buffer schematic".
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  4. RobbieK


    Jun 14, 2003
    Here's a nice link.

    The first or second fet circuits are fine. Use a 4M7-10M gate resistor for the piezo buffer, and a 470k-1M gate resistor for the magnetic buffer.

    For the mag/piezo blend, use a dual gang 25k linear pot for the blend, wired in the standard, cris-cross way. If you use an EMG blend bot (ebay), it will be pre-wired with the "cris-cross" on a little circuit board, plus it'll have a centre click.

    The real problem you may have is matching the output of the two sources. Most likely, the piezo will need a little extra gain, but not always. Magnetic pickups vary in output by magnitudes.
  5. giuseppecaporus


    Dec 19, 2013
    Thankyou i have all the info i Need 😊!
  6. fdeck

    fdeck Supporting Member

    Mar 20, 2004
    Madison WI
    HPF Technology: Protecting the Pocket since 2007
  7. I'm not sure I understand, how can these be used for blending a piezo and mag signal? Shouldn't the circuit have two inputs?
  8. giuseppecaporus


    Dec 19, 2013
    as i understed you must have to buffer on for magneticps pickup and 1 for peizo and than blend it togheter . the two one must have different gate value .
  9. ctmullins

    ctmullins fueled by beer and coconut Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    My semi-hollow uses a Cafe Walter PZP-1 to buffer a piezo; the output from the PZP-1 is then blended passively with a pair of Nordstrand Big Singles. Works fine. It might work a little better if they were blended using an active buffer, but it works fine as is.
  10. giuseppecaporus


    Dec 19, 2013
    so is has only the buffer for piezo , do somebody no if there'll a big difference with an additional buffer for magnetic pickup ?
  11. ex-tension


    Jun 11, 2009
    I've never had a piezo pickup and never blended buffered and passive pickups together. So, I don't have any experience about it. But even if I have it I can't tell that the difference is big or not. Only you can say how big "a big difference" is. So, a JFET buffer is simple&cheap enough to build and try. If you're going to build the buffer for your piezo pickup, build another one for the magnetic pickup. Then try it with or without buffer.

    Check again the page I posted before (cafewalter), see this link at the bottom of the page:
    "Schematic showing passive blend/vol/tone circuit for combining pickups"

    also, see the circuit here:

    This would give you some idea about the blend pot values.
  12. giuseppecaporus


    Dec 19, 2013
  13. ReidK

    ReidK Jst sy n t lssy cmprsn. Supporting Member

  14. giuseppecaporus


    Dec 19, 2013

    thankyou . now i'm just thinking of the power supply , cose my bass will have 18v for the preamp , 9v for the two buffer and
    9 v for onboard tuner and onboard db boost . will it work with 54 v power supply .

    i also find this on a site of my contry :http://www.op-electronics.com/en/index.php?controller=attachment&id_attachment=37
    will it work ?
  15. bassbenj


    Aug 11, 2009
    No this will not work as is. For one thing a ground is missing on the diagram on R4 and the cap. For a magnetic pickup buffer I'd lower R1 to about 500K (the usual volume control load for passive magentics) and raise C1 to .05 mfd or so to get the low frequencies. The output cap may or many not need the same treatment. If the pickup impedance is very low, the C1 cap may need to be the same value as the output cap C2. Key to needing higher cap values will be that low bass is rolled off.

    To use it as a piezo buffer, again fix R4 ground, and raise R1 to 10 megohms. Remove C1 as C1 is the piezio element! The other end of the piezo pickup is grounded, of course.

    Then these two buffers should be easily able to drive some passive blend control.
  16. ReidK

    ReidK Jst sy n t lssy cmprsn. Supporting Member

    That's a lot to put in a bass! I don't know where you could find a 54V supply that will fit in the same instrument as all that stuff, but fortunately you don't need that. All that equipment needs additional current, not additonal voltage. All you need (in theory) is two 9V batteries. Wire them in series and put a tap on the junction. That gives you one 18v source and two 9V sources. Keep in mind that only one of those 9V sources shares a ground with the 18V source, so if all the 9V equipment requires a common ground with the 18V preamp (which is likely), you won't be able to use the other 9V source. Depending on the current demands of the equipment, your batteries may not last very long, especially the one that's supplying everything. You might need another battery or two in parallel to get any usable service life.

    Wow... someone is actually selling that?! It might work by accident, but it certainly won't work well. To begin with, R4 and C3 do absolutely nothing and can simply be left out of the circuit with no effect. R3 does almost nothing (other than conduct) and can be replaced with a wire. You'd still have a circuit that doesn't work. This circuit certainly will not work with just any JFET as they claim, and I'm skeptical that it will work with any J201. If you do try this, leave out the led and the 1K resistor unless you really enjoy changing batteries.

    I suggest that you forget that one.

    It looks like they were trying to do something like this:


    There's a discussion of this circuit here.

    That's not a bad design, though it needs a supply bypass capacitor from +9V to ground.

  17. ReidK

    ReidK Jst sy n t lssy cmprsn. Supporting Member

    All good suggestions (I think the 10uF output cap is fine). If you must use this cricuit board, that should make it work. You still need to add a bypass cap from 9V to ground. I prefer the simpler input bias network, but that's me.