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Re: [micbuilders] Re: Panasonic WM-55A's dead?

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  • Scott Helmke
    ... I d think that you need a DC blocking capacitor between the capsule and the opamp input... and as Mike said, where s the ground reference to the + input?
    Message 1 of 11 , Oct 18, 2005
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      On Tuesday 18 October 2005 02:20, crazyyakuza wrote:
      > I added a schematic in the files section under my username. There are
      > no caps anywhere except on the power rails. I know the problem is
      > with the mic capsule itself, because it stops working when I change
      > only the capsule, as indicated in the schematic.
      >
      > Is it possible I disconnected the source of the FET from ground?

      I'd think that you need a DC blocking capacitor between the capsule and
      the opamp input... and as Mike said, where's the ground reference to the
      + input?

      -Scott

      --
      ---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
      And you'll visualize not taking any chances
      But meet them halfway with love, peace, and persuasion
      And expect them to rise to the occasion
      (from "Glad Tidings", by Van Morrison)
    • crazyyakuza
      The circuit is not the problem, as it works fine with a good mic. The ground reference is through the the 2.2k pullup resistor. Adding a DC blocking cap would
      Message 2 of 11 , Oct 18, 2005
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        The circuit is not the problem, as it works fine with a good mic. The
        ground reference is through the the 2.2k pullup resistor.

        Adding a DC blocking cap would do two things:
        1) Remove the ground reference that you ask about (although I'm using
        FET inputs, so that shouldn't matter, as I don't really need input
        bias current).
        2) Clip the bottom half of my signal, as I am running the op-amp off a
        single supply.

        (I am relying on my soundcard to do eventually DC blocking, which it
        seems to do.)

        --- In micbuilders@yahoogroups.com, Scott Helmke <scott@s...> wrote:
        >
        > On Tuesday 18 October 2005 02:20, crazyyakuza wrote:
        > > I added a schematic in the files section under my username. There are
        > > no caps anywhere except on the power rails. I know the problem is
        > > with the mic capsule itself, because it stops working when I change
        > > only the capsule, as indicated in the schematic.
        > >
        > > Is it possible I disconnected the source of the FET from ground?
        >
        > I'd think that you need a DC blocking capacitor between the capsule and
        > the opamp input... and as Mike said, where's the ground reference to
        the
        > + input?
        >
        > -Scott
        >
        > --
        > ---- Scott Helmke ---- scott@s... ---- (734) 604-9340 ----
        > And you'll visualize not taking any chances
        > But meet them halfway with love, peace, and persuasion
        > And expect them to rise to the occasion
        > (from "Glad Tidings", by Van Morrison)
        >
      • dayVel
        ... There are ... capsule and ... What voltage do you measure at the opamp output pin to ground in the good and bad circuits?
        Message 3 of 11 , Oct 19, 2005
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          --- In micbuilders@yahoogroups.com, "crazyyakuza" <darthmonkey42@h...>
          wrote:
          >
          > The circuit is not the problem, as it works fine with a good mic. The
          > ground reference is through the the 2.2k pullup resistor.
          >
          > Adding a DC blocking cap would do two things:
          > 1) Remove the ground reference that you ask about (although I'm using
          > FET inputs, so that shouldn't matter, as I don't really need input
          > bias current).
          > 2) Clip the bottom half of my signal, as I am running the op-amp off a
          > single supply.
          >
          > (I am relying on my soundcard to do eventually DC blocking, which it
          > seems to do.)
          >
          > --- In micbuilders@yahoogroups.com, Scott Helmke <scott@s...> wrote:
          > >
          > > On Tuesday 18 October 2005 02:20, crazyyakuza wrote:
          > > > I added a schematic in the files section under my username.
          There are
          > > > no caps anywhere except on the power rails. I know the problem is
          > > > with the mic capsule itself, because it stops working when I change
          > > > only the capsule, as indicated in the schematic.
          > > >
          > > > Is it possible I disconnected the source of the FET from ground?
          > >
          > > I'd think that you need a DC blocking capacitor between the
          capsule and
          > > the opamp input... and as Mike said, where's the ground reference to
          > the
          > > + input?
          > >
          > > -Scott
          > >
          > > --
          > > ---- Scott Helmke ---- scott@s... ---- (734) 604-9340 ----
          > > And you'll visualize not taking any chances
          > > But meet them halfway with love, peace, and persuasion
          > > And expect them to rise to the occasion
          > > (from "Glad Tidings", by Van Morrison)
          > >
          >


          What voltage do you measure at the opamp output pin to ground in the
          good and bad circuits?
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