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HELP WITH WIRING IN A SILICON DIODE

Discussion in 'Pickups & Electronics [BG]' started by rymiraflores, Jul 10, 2013.

  1. Jul 10, 2013 #1
    rymiraflores

    rymiraflores

    Jan 17, 2009
    I have wired in a diode as follows and nothing happens...what have I done wrong?
    Diode ..centre lug on 2-way switch to earth on tone pot.
    Wire from outside lug on switch to pos on volume pot ( white wire on EMG Hz Pu.)
    If I were to wire the diode in so that it would be on permanently what options do I have about where I put it?
     
  2. Jul 10, 2013 #2
    Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    Are you trying to make an on-board diode clipper for distortion effects? It won't work. A silicon diode has too much forward voltage to begin conducting (typically 0.6 - 0.7 volts) at typical bass pickup output levels.

    At the very least, you need to use a diode with a lower forward voltage, like a germanium diode (1N34 type is one example) or a Schottky diode. The diode will be wired from the pickup's "hot" wire to ground. You will get some distortion but it will be at a lower volume than your clean tone.
     
  3. Jul 10, 2013 #3
    rymiraflores

    rymiraflores

    Jan 17, 2009
    Are you sure? Emg Hz 40 put out around 3 volts.
     
  4. Jul 10, 2013 #4
    line6man

    line6man

    Jun 20, 2008
    Close to Los Angeles, CA
    No they don't. That's an extreme peak.

    He is talking about forward voltage drop, however.

    You need to make sure you're using a diode with a low forward voltage drop and a fast switching speed.

    If you want it to be permanently wired in, it should go parallel to the signal path. Choose the part of the circuit in which the impedance does not vary with the volume pot's setting. If you have a master volume, that would be parallel to its input.
     
  5. Jul 10, 2013 #5
    rymiraflores

    rymiraflores

    Jan 17, 2009
    Previously everyone suggested that a 1N4148 would work well or a red LED...What would you suggest and what output voltage would you think was more realistic to expect from an EMG Hz40'
     
  6. Jul 10, 2013 #6
    line6man

    line6man

    Jun 20, 2008
    Close to Los Angeles, CA
    I don't know what people are using, off hand. Maybe someone else can chime in.

    Pickup voltage is hard to determine, because it varies continuously, and it is different for every frequency. Overall, transient peaks might hit a volt or two. Normal playing could be in the hundreds of milliVolts range. A greater concern is for signal impedance.
     
  7. Jul 10, 2013 #7
    rymiraflores

    rymiraflores

    Jan 17, 2009
    It looks like the nominal forward voltage for 1418s is 0.7 volts..I asume that if I use 2 the FV will drop to 3.5 ish..will they ned to be ; parallell, in series or in opposite directions to do this?
     
  8. Jul 10, 2013 #8
    line6man

    line6man

    Jun 20, 2008
    Close to Los Angeles, CA
    That's way too high! Get a proper switching diode with a low forward voltage drop.

    You can try different combinations of diodes for different sounds.
     
  9. Jul 10, 2013 #9
    rymiraflores

    rymiraflores

    Jan 17, 2009
    Do you think a Schottky 1N5819.FV 0.3v..would work ? or do I need to go lower still?
     
  10. Jul 10, 2013 #10
    Stealth

    Stealth

    Feb 5, 2008
    Zagreb, Croatia
    0.3 is already closer to what's idea, so two Schottkies should work well.
     
  11. Jul 10, 2013 #11
    iiipopes

    iiipopes Supporting Member

    May 4, 2009
    +1 on the 1N34. I believe that is the type of diode that Jack Bruce used to get his grind.
     
  12. Jul 10, 2013 #12
    rymiraflores

    rymiraflores

    Jan 17, 2009
    Thanks..looks like the 1N34A is the way to go.starts conducting at 0.1 V...should work.