In article writes:

Hey, I've got an audigy2 soundcard in my computer, and someone told me
that i can't use my dynamic mic straight in to the microphone port on
account of a 3V DC bias that'd cause problems with dynamic mics

Month after month, this is the most frequently asked question at Shure...
http://shure.com/support/technotes/app-soundcard.html

There are some good tips in there, but unless I missed it, it doesn't
really address the question (or rather the questions that should have
been asked), and that's whether:

1. (You probably know the answer to this one) Will the bias voltage
affect the SM57? Because of the limited current, I doubt that it
will send the diaphragm slamming into the wind screen (or back into
the body) but putting a DC bias on a transformer could affect its
linearity or headroom.

Turns out that this is actually addressed in another application note:
http://www.shure.com/support/technot...-phantom1.html, which
is referenced in the above app-soundcard note. It says (briefly) that
a dynamic mic should not be used with an input that provides bias
voltage due to the possibility of damage to the mic (a safe answer),
but that it's possible to install a blocking capacitor (value unspecified)
to block the DC from the microphone. It would certainly be feasable to
make a special cable with an XLR on one end, a mini plug on the
other, and a 20 uF or so capacitor in series with the hot lead.

2. (You probably don't want to answer this one because of liability
issues) Will the current drain caused by connecting the mic to the
sound card mic input with a bias voltage, essentially a short
circuit to the bias voltage source, damage the sound card?

I suspect that the answer to both is "no" but the orignial poster
probably wants to hear it from someone who has actually tried it and
not blown up an SM57 or an Audigy card.




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