( LO Z ) Fearn and Shure question

[scorpiwoman]

I want to understand why the shure sm57 is marked Lo Z. I thought that stood for low impedance. Same with the Fearn VT mic pre. Would this setting work better with low impedance microphones (ribbons).

[Mixwell]

From the VT1 Manual,

The Lo-Z position should be used only with certain microphones (e.g. the Neumann TLM-
series, some newer Schoeps) that exhibit an extremely low output impedance. These micro-
phones typically feature a transformerless output. In the Lo-Z position, an impedance-match-
ing network is inserted ahead of the input transformer and this optimizes the VT-2 perform-
ance with these microphones. The best position can be determined by listening, although the
difference may be subtle on many mics.

[scorpiwoman]

Thanks Adam,

Is the LO-Z on the Fearn 300ohm as on many mic pres... Great River, chandler, Neve. I guess I'm confused on the difference of the impedance. The Great River site claims using the low impedance on their pre would do little to change the sound of a condenser mic due to the amp buffering.

Also what's up with the sm57 saying LO-Z on the side of it?

[Mixwell]

From the Shure Web Site;

SM57 Impedance
Rated impedance is 150 ohms (310 ohms actual) for connection to microphone inputs rated low impedance.

[albert]

Use whichever impedance on the preamp that sounds best.

But understanding the science will help you make good estimations as well.