At 9:01 AM +0000 12/29/06, jpbeale wrote:
>--- In "Raimund Specht"
><> wrote:
>> I agree that the relatively high output impedance of 1 kohm results in
>> a higher noise level. Though, I guess that a 150 ohm source might
>> improve the noise figure by more than 2 dB.
>
>I redid the measurement with a different attenuator, with Z=3D150 ohms
>out this time; all the rest of the setup was the same. The total noise
>floor was improved by 1.6 dB. Some small noise spikes also appeared,
>eg. around 15 kHz. I am not sure if that is internal to the unit or
>not. I took down the setup, reassembled it, and re-ran the test. I got
>the same results again to within 0.1 dB.
>
>Measured MZ-RH1 input noise level (150 ohm source)
>
>-122.2 dBu (unweighted)
>-124.4 dbu (A weighted)
>
>http://beale.best.vwh.net/measure/audio/MZ-RH1_Mic_30_150Z.htm
>
>J. Beale Dec.28 2006
>
Hi J Beale--
Your input noise numbers seem better than Richard's for his NH700
http://www.wildlife-sound.org/equipment/himd/himdmyths_meas.html
and Bruce's for his NH800:
http://bioacoustics.cse.unsw.edu.au/archives/html/naturerecordists/2006-04/=
msg00301.html
In practical application, Richard concluded that the noise of the mic
pre in his Hi-MD recorder at gain "28" is faintly detectable within
the signal created by a Sennheiser mkh-40 mic with 25mV/Pa and
self-noise of 12dBA. In my experience with recorders, this is very
commendable performance for a low cost unit.
As you may have read, all of the Hi-MD models appear to have the same
mic pre AD circuit. I recall Richard mentioning his MZ-RH1 having
slightly more noise than his NH700 perhaps due to the different kind
of display in the MZ-RH1. A listening test comparing a MZ-RH1 to a
earlier model yielded no detectable difference by ear, but maybe they
are some performance differences in the units being produced.
In your ratings of the performance of your Hi-MD recorder,
http://beale.best.vwh.net/measure/audio/MZ-RH1_Mic_30_150Z.htm to
which audio recorders are you making this comparison or "poor" and
"average?" Rob D.
--
Rob Danielson
Peck School of the Arts
University of Wisconsin-Milwaukee
http://www.uwm.edu/~type/audio-art-tech-gallery/
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