>> http://www.avisoft.com/recordertests.htm
>
> I note that there is no mention of the equivalent SPL of the mics' input =
noise.
Dan,
It's an interesting table as it goes, but it doesn't take into consideratio=
n
a low impedance mic going into a mid to high impedance input.
What is little understood is "optimum noise impedance" which is not the sam=
e
as the input impedance.
A 200 Ohm mic outputs a voltage 1/10th of an equivalent 20 KOhm mic but wit=
h
10 times the available current for the same output power. (In power decibel=
s
dBu not dBV) If, as I suspect, on an affordable recorder, the built-in mics=
will have an impedance around 20 K with the input stage optimised for this.=
A 1:10 transformer on a 200 Ohm mic would give +20 dB lift (about) greatly=
reducing the relative input noise.
Back to noise impedance. It is possible to optimise a high impedance input=
but with a low noise impedance, but then it would not be optimum for a high=
impedance mic, at least not on an affordable recorder.
David Brinicombe
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