when I received my 722 I immediately connected a pair of NT1As and I
was very disappointed because I got some extraneous noise bands above
20 kHz. I tested again after having disconnected almost all
electronics from the main power and the noises disappeared.
Many consumer electronics maintain their internal power transformer
on all the time, even when we believe to have switched off (this
increases power consumption, of course). Most of the internals
transformers, an also all the detachable power units we use with
laptops and other electronics, are based on switching transformers
that may generate either acoustic (sonic and/or ultrasonic) or
electromagnetic interferences even if the attached equipments are
off; if the attached equipments are on, the interferences may vary
depending on the power consumption.
Gianni
At 08.01 10/01/2006, you wrote:
>It could be something in the mic pre or even the phantom circuit. As
>you have initiated, testing the 670 with different mics with and
>without the Rolls in different locations should help pin down the
>source. The solution, however, might not be easy to find. With
>low-level sounds and high gain, we're asking the gear to perform
>flawlessly at its limits and then amplifying the results to a high
>degree. The awareness that recordings usually have small quirks to
>obvious inaccuracies has encouraged me to learn to use filtering to
>help make the sound coming from the speaker better resemble what I
>heard in the field. EQ is often over-done but done right, the
>difference it can make is very exciting in my opinion. I hire Peet
>for everything above 10K (the loss settled in over the last year,..)
>I noticed in the spectral graph on the movie that the Rolls->HiMD pre
>did not pass the 13KHz environmental whine as well as the 722 or MP2
>and that the high end response above 8K was lower in general with the
>HIMD pre. Rob D.
>
>At 7:59 PM +0000 1/9/06, John Hartog wrote:
> >When I look at spectrograms of recordings I made using NT1-A's with a
> >PMD-670, I notice a narrow band about 200Hz wide between 16K and 21K.
> >I'm pretty sure it's from the recorder not the mics because it is
> >always stronger in the left channel. The band drifts over time, for
> >instance it might start out at 16K and over an hour or so it gradually
> >rises to 19K. My ears cannot hear it but frequency analysis shows a
> >5dB spike. The problem seems to disappear using the NT1-A's with a
> >Rolls PB224 and my new MZ-RH10, though I haven't had much time to test
> >that thoroughly.
> >
> >Relating this to nature recording:
> >Does a band like that compromise the audible quality of my recordings?
> >Should I just leave it or try to filter it out?
> >
> >-John Hartog
> >
> >
> >
> >--- In Rob Danielson <> wrote=
:
> >>
> >> Lucky for you that 13K stands out so audibly, Rich! It seems to be
> >> an actual sound-- something I cannot find the source of, possibly
> >> even a transmission. I had everything off, even downstairs, and
> >> everything running on DC. Here's a spectrogram of the clock test
> >> movie that Gianni sent back in November:
> >> http://www.uwm.edu/~type/Mic%20Preamps/MicroTrack_NH900_722Compare2.j=
pg
> >>
> >> Gianni recently asked about some High Hz banding he was seeing with
> >> his NT1A's, so to get a sense of what's inherent my NT1A's, I made
> >> some spectrograms of simultaneous recordings made in a mid-winter
> >> very quiet, remote wood at about 2am. (Way up in the hollow Rich).
> >> The Sennheiser mkh80 is included for comparison.
> >>
> >> http://www.uwm.edu/~type/Mic%20Preamps/NT1A_MKH80_Remote2AMPresSpect.=
jpg
> >>
> >> I could not find any significant banding at any frequency including
> >> 13K, so this seems to confirm the 13K sound was recorded, not
> >> self-noise. The sample is 3 seconds long and the vertical scale is
> >> 0-24KHz. Rob D.
> >>
> >> =3D =3D =3D
> >>
> >> At 4:34 AM +0000 1/9/06, Rich Peet wrote:
> >> >--- In Rob Danielson <>
> >wrote:
> >> > In this test,
> >> >>
> >> > >
> >http://www.uwm.edu/~type/Mic%20Preamps/MicroTrack_NH900_722Compare2.mov
> >> >>
> >> >....
> >> >
> >> >Did you add a high pitched whistle to go with your clocks in your
> >> >recording area or are you now chasing whistles from your nt1-a's lik=
e
> >> >I have had to do in the past with my old mics?
> >> >
> > > >Rich
> > > >
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
>--
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6
--------------------------------------------------------------
Gianni Pavan
Email
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel +39-0382-987874
Fax +39-02-700-32921
Web http://www.unipv.it/cibra
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