Klas wrote:
> Hmmm, might be a mistake here.
>
> Pin 3 of PRO6 IS connected to a 100 ohms resistor and 22 mfd/50 v
> condensor to ground, just as the usual and as the MKH circuit you
> refer to. (But connected to + instead)
Yes, that is exactly the mistake. A phantom-powered microphone should
draw identical currents from pin 2 AND pin 3 through the microphone
electronics to ground (pin 1). This is achieved by a matched pair of
resistors (R12 and R13, 3k3 ohms in the schematic that I refer to).
These two resistors are in series with the two matched 6k8 resistors
that are connected to +48V inside the recorder. In addition to that,
there should be no asymmetric capacitive loads to the pins 2 and 3.
Anything else would be wrong and could cause trouble.
Regards,
Raimund
> I think Sennheiser had that solution, as they could use a 16V
> tantalum condensor to "ground" the cold output, in this case pin 2..
> As you can see on the diagram, there is only 10 v between the 48v and
> the 38v +rail. High voltage tantalum condensors were expensive not
> long ago, and connecting the cold output to + instead of to ground,
> is from that perspective really smart.
>
> Klas.
>
> At 21:17 2007-03-22, you wrote:
> > > Raimund Specht wrote:
> > >
> > > >Yes, that impedance matching will make sure that the disturbances
> > > >entering in the cable will be compensated. However, in this
way, the
> > > >noise originating from the phantom power will only be present
on pin
> > > >2.
> >
> >Dan Dugan wrote:
> > > If you're talking about noise from the phantom power source in the
> > > recorder, it will be applied equally (depending on the accuracy of
> > > the series resistors) to pins 2 and 3, assuming equal impedance
> > > (which is why the dummy network on pin 3 of the mic) and will be
> > > canceled by the balance of the mic preamp.
> >
> >Yes, of course. I just tried to explain to Klas that his unbalanced
> >microphone output (where pin 3 is not connected to the usual series
> >resistor) is not able to tolerate any potential phantom power noise.
> >The debate started here:
> >http://tech.groups.yahoo.com/group/naturerecordists/message/27021
> >
> >Raimund
> >
> >
> >
> >
> >"Microphones are not ears,
> >Loudspeakers are not birds,
> >A listening room is not nature."
> >Klas Strandberg
> >Yahoo! Groups Links
> >
> >
> >
>
> Telinga Microphones, Botarbo,
> S-748 96 Tobo, Sweden.
> Phone & fax int + 295 310 01
> email:
> website: www.telinga.com
>
>
>
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