thanks Dan!
will post some samples once I get this figured-out
/:b
{ brad brace } <<<<< >>>> ~finger for pgp
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On Tue, 7 Apr 2009, Dan Dugan wrote:
> > now I'd like to run about 500' of 3.5mm stereo cable down to
> > the creek (and maybe _in the creek -- the mic in a plastic
> > soda bottle)
>
> resonances inside the bottle will dominate the sound...
>
> > behind my place where all the marvelous
> > serenades occur this time of year...
> >
> > I'm thinking of recording direct to DVD/computer if
> > possible... or HiMD
> >
> > is the cable length a problem?
> > recommended vendors appreciated
>
> Any twisted pair with shield will do. I've run 100' unbalanced stereo
> like that, in the city. Expected taxis to break in, but it was fine.
> 500' may be pushing it, but the only effect of too long will be a
> rolloff of high frequencies. You'll want to keep cell phones off
> around such extended unbalanced circuits.
>
> I'm not an engineer but I play one at work. Let me try to run the
> numbers (real engineers correct me if I'm wrong):
>
> Take the very rugged Belden 8451--not a low-capacitance cable, so a
> worst case. Capacitance between one conductor and other conductor plus
> shield is 67 pF/ft. 500 feet is a capacitor of 33,500 pF or .033 uF.
>
> Assume a worst-case PIP microphone source impedance of 3K Ohms.
>
> Slide rule says that combination is 3 dB down at -- oops -- 1600 Hz.
> That would sound pretty dull. A 200-Ohm source on the same cable would
> be 3 dB down at 22 KHz. That would work--so you need a low-impedance
> mic out there. And in that case you might as well go pro and wire it
> balanced with a twisted pair for each of 2 mics.
>
> Plan B: put the recorder down at the creek. Then run the headphone
> circuit back. That has a low source impedance and should be just fine
> through 500' of cable.
>
> -Dan Dugan
>
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