I'm going to connect an electret mic (WM-61A) to my computer's "mic in", and am very confused on the reasoning behind a couple different diagrams/schematics that could possibly be used to do this with. The first one is from a thread on Head-Fi and seems to be the standard that everyone uses there: enter image description here This is good to me, but then when I did a search for a couple different options, I found this: enter image description here There's also another schematic using an AD654 op-amp specifically for phantom power. The one above claims to provide a "Phantom Ground"; what exactly is this compared to the first schematic and compared to a virtual ground? Could any of these be used for my purpose?

Please and thank you for any guidance given!


The extra circuits you have researched do not apply if all you are trying to do is interface an electret microphone to a computer mic-in port.

Those extra circuits produce a mid-rail voltage (such as 4.5 volts when using a 9 volt battery) and are useful when developing an op-amp amplifier circuit and all you have is a single power supply such as a 9 volt battery. The mid-rail voltage can be regarded as ground for any audio inputs or outputs. It is sometimes called "phantom" or "virtual" ground but I prefer the term "midrail generator" because it says what it does. You don't need this for what you are wanting to do.

  • \$\begingroup\$ That's exactly what I needed to know. I figured they weren't the same as they looked to make a virtual ground, or else called "midrail generator" like you said. I have a better understanding now, so thank you very much! \$\endgroup\$ – topher Dec 28 '16 at 15:17
  • 2
    \$\begingroup\$ Currency of thanks is upvoting or formal acceptance of an answer but leave it a day to see if any new answers come along that might be better. \$\endgroup\$ – Andy aka Dec 28 '16 at 15:36

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