SM57 and bias power

FAQ #2578 Updated February 22, 2018

Question:

I've read that dynamic mics don't like bias power. I've also read that the SM57 will "ignore" phantom power.

I know that phantom power and bias power aren't the same thing, so my question is, will the SM57 also "ignore" bias power?

If not, where can I get the required hardware to block the bias power?

Answer:

I've read that dynamic mics don't like bias power.
* Correct. This is because bias is provided via an unbalanced circuit.

I've also read that the SM57 will "ignore" phantom power.
* Correct.

I know that phantom power and bias power aren't the same thing,
* Correct.

so my question is, will the SM57 also "ignore" bias power?
* No, it will not ignore it.

If not, where can I get the required hardware to block the bias power?
* Blocking the bias is typically done via a capacitor. The size and position of the capacitor depends on the bias circuit. Here is a typical bias blocking circuit:

Assumptions:
SM57 pin 2 to tip of phone jack; tip also contains 5 volts of bias.
SM57 pin 3 and pin 1 to sleeve of phone jack.

To block bias:
Place a capacitor in series with the SM57 pin 2. This will pass audio but block the DC bias.
Value of the capacitor: 10 microfarads; rated at 16 WVDC; the negative end of the capacitor connects to the SM57.

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