Very well put Scott and a good synopsis of the state of the art past and pr=
esent.
One caution here - A lot of phantom power these days is supplied by cheapo =
(read noisy) DC to DC converters in battery operated preamps and computer i=
nterfaces. The 48V figure can often be a euphemism as well. YV (not M) MV f=
er sure. They get away with it for users who are recording music, especiall=
y electric, but faint, distant bird calls usually don't come with buzz or n=
oise of their own and anything present on the 48V can be objectionable...
If you are going to use the phone line, I'd shield it and toss in a couple =
of caps at both ends. Order up a hunk of that Mogami double center conduct=
or cable if you've got a extra few bucks or put it on your Valentines day l=
ist. No, I can't vouch for the efficacy of that but I'd do it out of princ=
iple and just for the fun of the project if I was of a mind to and it would=
only help I suppose.
Gotta admit, I never thought of that one but I live off grid and phone is a=
mile or so away.
Randy
--- On Sun, 1/3/10, Scott Fraser <> wrote:
> From: Scott Fraser <>
> Subject: [Nature Recordists] Re: Phantom Power. Question from The Ghost W=
ho Walks :-)
> To:
> Date: Sunday, January 3, 2010, 7:13 AM
> <<One of the things I don't
> understand is how the range of voltage for=A0
> Phantom Power can vary between 9-52V DC and whether the
> voltage=A0
> difference makes an "audio" difference.>>
>
> Officially Phantom power is 48 volts DC, but in the past a
> number of=A0
> lower priced mixing desks didn't bother to incorporate a
> power supply=A0
> providing a 48 volt tap in addition to the + & - 12 to
> 18 volt rails=A0
> needed for the circuitry. They started supplying Phantom
> voltages in=A0
> the range of 24 to 36 volts, which many condenser mics are
> happy with.=A0
> Neumann mics specifically (I know from personal experience)
> will not=A0
> operate at less than 48 volts without seriously compromised
> dynamic=A0
> headroom, but the makers of the less than fully pro desks
> gambled that=A0
> their end users would likely not also be using high end
> microphones.=A0
> Today it's quite rare to find less than 48 volts available
> on any mic=A0
> preamp. Generally speaking most mics will exhibit higher
> self noise &=A0
> reduced dynamic range when powered by less than 48 volts.
> Electret=A0
> condensers are usually less affected, since the Phantom
> voltage is=A0
> only running the impedance converter circuit, not
> polarizing the=A0
> diaphragm. Generally electrets running on an internal 1.5
> volt battery=A0
> are rather noisy because they are designed to hit a low
> price point=A0
> resulting in a number of design compromises.
>
> Scott Fraser
>
>
>
>
> ------------------------------------
>
> "While a picture is worth a thousand words, a
> sound is worth a thousand pictures." R. Murray Schafer via
> Bernie Krause
> Yahoo! Groups Links
>
>
> =A0 =A0
>
>
>
|