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9v preamp for acoustic guitar

Discussion in 'General Electronics Discussion' started by kiwi5000, Dec 28, 2012.

  1. kiwi5000

    kiwi5000

    12
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    Dec 27, 2012
    Hello,

    I'm making a 9v preamp piezo pickup for my acoustic guitar. I've found instructions here...

    http://blog.makezine.com/2011/12/20/collins-lab-diy-contact-mic/

    I've put them in DipTrace and I want to make a simple PCB to etch on to a copper blank.

    I've attached two diptrace files for review. And I'll add a picture too.

    I just need some advice or guidance if I'm on the right track. Any thoughts or comments is appreciated.

    I've ordered the parts along with a perf board so can have a mock up before I do the final one.

    Thank you.
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,230
    1,861
    Nov 17, 2011
    I have bo access to diptrace. Can you post a PDF of the layout`?

    For this simple circuit the layout should be straightforward and follow almost exactly the schematic wiring. Personally I wouldn't even bother to etch a PCB, but I assume it is to satisfy your personal curiosity, so it's perfectly o.k.
     
  3. kiwi5000

    kiwi5000

    12
    0
    Dec 27, 2012
    pdf

    Attached is the PDF of the copper pour.

    You're right, I'm really just wanting to make a PCB maybe with a graphic or text on it. :)

    Does it look right? I can tell how the schematic goes and how to wire it that way but the PCB doesn't look right but I'm not sure.

    Thanks.
     

    Attached Files:

  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    Hi kiwi, welcome to the forums :)
    I don't see any connection to the middle pin of the JFET.
    Also several connections that should be grounded aren't connected to the ground plane.
    You also need to specify the part number of the JFET so we know its pinout.
    Personally I would make the layout more compact. You can see that there's a resistor connected to each pin of the JFET; I would put them side by side, with the JFET at the end, and run three short straight tracks from the JFET to the resistors. Then add the other components.
     
  5. kiwi5000

    kiwi5000

    12
    0
    Dec 27, 2012
    more pic

    The auto router made it 2 layer so I redid the routs myself so it makes a bit more sense now. I want the piezo, jack and 9v to have it's own little soldering holes. Is that normal or do I just solder them directly to the resistors/cap connections?

    The part # is MPF102 for the transistor.

    I'll try that layout next. Thanks for the help!
     

    Attached Files:

  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    Normally, wires have their own holes. And it's normal to put the holes for related wires in the same area, and connect them into the rest of the circuit using tracks. So, for example, the two wires that go to the pickup should connect to two pads that are next to each other.

    That's the conventional way. You can solder wires to component terminals; this saves some space. But this makes it more likely that a wire will accidentally be soldered to the wrong point, and if the wire breaks off, it may be hard to see where it was connected. So it's best to have individual pads for the wires, and to put related wire connection points together.

    In a commercial design, off-board connections would be made using plug/socket connectors.

    Your new layout is better, but it still has errors. It looks like C3 is connected between the gate and drain of the JFET. R1, R3 and R4 aren't connected to the ground plane. Also, I think your resistor outlines are much wider than they need to be. Small resistors can be spaced at 0.1 inch pitch.

    The MPF102 doesn't seem to be readily available. N-channel JFETs available from Digikey are J105, J106, J107, J111, J112, J113, PF5102. Mouser have 2N5485 and 2N5486.
     
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