At 2:57 PM +0200 9/3/06, Klas Strandberg wrote:
>Folks, I assure you, there is no way to reveal noise generated by the DC
>chopper. All you can do is to connect batteries, supplying the phantom
>power, and hear if the noise disappears.
>When you have such noise, like when I use the MT24/96 - I don't even know
>if the noise is generated in the mic or in the MT or "everywhere".
>
>Klas.
Hi Klas--
I'm not familiar enough with electronics to provide you test method
that Eric used. If I thought we had enough evidence that the Rolls
was the culprit, I'd forward this to him. His input is in high demand.
He measured the noise floor with two MK 2/CMC6's [11 dB(A), 15 mV/Pa]
and found it to be -120 dBV. The output impedance of the phantom
supply is 6k81, the the output impedance of microphones is 50 Ohms.
He asserts the noise voltage from the phantoms supply is attenuated
by the voltage divider of 6k81 in series with 50 Ohms. His bottom
line, the Rolls would add no noise to these mics. He promised he
would put the noise relation into a graph when he gets a chance.
On the perceptual impact/practical use side, we have lots of
recordists out there with NT1-A's on Rolls and none have asserted
noise problems associated with the Rolls that I've talked with. I
take Eric test to suggest that the noise it contributes is at most
10dB(a) under that of the Schoeps MK 2/CMC6's [11 dB(A)] and that of
the Hi-MD pres. This QuickTime movie listening test starts off
comparing NT1-A's ->722 and NT1-A->Rolls->722 (phantom off). It
suggests to me the Roll's self noise is ~-10dB less than the noise
floor of the NT1-A's/722 pre combination.
http://www.uwm.edu/~type/audio-art-tech-gallery/pages/page_38.html
The free video player, VLan, gets around having to have QuickTime on your P=
C.
http://www.videolan.org/
Rob D.
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