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Re: Low-Z Mics vs. High-Z Mics ???

Subject: Re: Low-Z Mics vs. High-Z Mics ???
From: Mike Feldman <>
Date: Sat, 21 Aug 2004 14:05:49 -0500
Dave J wrote:

> I'm confused. I thought all XLR mics were low-Z,
> but now I'm not sure.

Most, but not all.  XLR is a connector, not an
interface standard.  With an XLR typically pins
2 and 3 are the AC (audio) circuit and they should
present (and accept, for the preamp) same impedance,
which makes it a balanced circuit.

But you can wire an unbalanced circuit to an XLR
(typically shorting pin 3 to pin 1, which is the shield.
Balanced or unbalanced is independent of low-Z or high-Z
but usually low-Z mice have XLRs, and high-Z sources,
like some mics, and guitar/bass electromagnetic pickups
are high-Z, and often have a two conductor co-axial
connector like a 1/4" phono plug.

> Is 1000 ohms low-Z or high-Z ??? Thanks.

1000 Ohms is approaching high-Z.  Low-Z is
typically 300-600 Ohms, and high-Z is typically
2000-10,000 Ohms.  And there are very high-Z
audio sources, for example piezoelectric pickups,
which might be a megOhm or more.

In general, to avoid distortion from "shorting out"
the source, you want the preamp "sink" impedance to
much larger than the source impediance.

So a low-Z mic into a high-Z preamp input is mostly OK,
although some low-Z mics need loading to sound their best.

Hope that helps and doesn't confuse you more.
If you've got more questions, ask.

-- Mike


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