I noticed he's doing something funny with the noise figures he quotes
(-157 dbFS). If the noise comes from the 6800 ohm resistor only, then
the noise would be -119 dbu, just like every other phantom supply. That
gives a full-scale reference of +38 dbu, or an unlikely 62 v (remember,
phantom power is only 48 v, +36 dbu). Fortunately mics have capacitors
which (I think) will kill some of the thermal noise. Maybe the internal
resistance of a capacitor adds thermal noise, but the resistance can't
be high, so I doubt the added noise will be either.
Bruce Wilson
http://science.uvsc.edu/wilson
-----Original Message-----
From:
On Behalf Of Rob Danielson
Sent: Tuesday, June 27, 2006 10:16 AM
To:
Cc:
Subject: [Nature Recordists] 2Phant Core Sound Portable Phantom (was How
would you clean up this file?
Hi Aaron--
Apologies for the subject line change. Good find. Being able to see
the state of the batteries is also a nice addition.
The unit seems of special interest to people with low-noise phantom
powerred mics and non-phantom recorders or recorders with poorly
performing phantom circuits. Some of the later seem to have been
introduced to the market. The first question that jumps to my mind is
how does one know if the $200 cost difference is better invested in a
2Phant or perhaps towards better mics?
If I assume that the performance of the phantom supply in the Sound
Devices 722 is among the best in terms of noise performance, one way
to start this evaluation is to compare:
NT1-A-> PB224-> 722 (Phantom Off)
and
NT1-A->722 (Phantom On)
which I've done several times with consistent results. One of them is
at the head of this test:
http://www.uwm.edu/~type/audio-art-tech-gallery/pages/page_38.html
I'm cc-ing this to Eric Benjamin who is testing the PB224 along with
the WL-93 and other mics in case he has comment.
Rob D.
=3D =3D =3D =3D
At 1:20 AM -0700 6/27/06, Aaron Ximm wrote:
>Interesting new 2x phantom powering module from Core. Pricey at $275
but it
>has some nice features (the ability to swap batteries without
interrupting
>use is nice!).
>
>Interestingly Len claims the PB224 puts out less than 48V, he's got an
>incomplete section comparing the new box vs. various other phatom pow
>
> http://core-sound.com/2Phant/1.php
>
> aaron
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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