Rudy said:
>Test methodology:
>An MKH-800 was connected to a Grace V3 mic-pre A/D with a gain of 55
dB. After a slate was made, the mic was placed into a foam-lined box
in a relatively quiet room to minimize the contribution from noise in
the surrounding acoustical environment. The left channel of Grace
preamp was terminated in a 200 ohm dummy load. V3's dither noise
turned OFF.
>Sampling rate =3D 96 kHz, 24 bit data was recorded into Fostex FR-2. 24
bit 96 kHz stereo files were recorded an analyzed in Adobe audition's
Frequency Analysis window.
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OK, this is almost exactly what I need to do to characterize mikes I have,=
the Transit 24-bit interface recording to a laptop, and a preamp I will
probably be building.
I was considering building a 'foam-lined box' for this purpose. Can Rudy or=
others give some info on how you did this, size, material etc??
Next: I have a couple of Shure 183's that I'd like to characterize. They
have a rated output impedance of 1800 ohms, higher than I expected. Am I
right that I'd need to terminate the 'other' input in 1800 ohms to fairly
assess the residual noise from the preamp? Is 1800 ohms high enough to
require a special low-noise resistor for accurate results?
I really appreciate feeling I'm close to real help with this group, though=
in Africa.
Regards, Terry King ...On The Mediterranean in Carthage, Tunisia
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