At 23:19 2007-03-21, you wrote:
>Hi Klas,
>
>The differences might also be caused by the design of the microphones.
Yes, but not as a rule.
If you take the MT24/96, for example, you can shorten the phantom
power by hundreds of nF, - the noise still lives on inside the machine.
If you connect another microphone, perhaps less power consuming, it
works just fine. But you don't know why and there is no (known to me)
way to find out.
This is what I hate: Modern powering devices seem to be unreliable, too oft=
en.
>A fully balanced microphone circuit should work properly even if the
>supplied phantom power is not very clean. The balanced input of the
>recorder would reject those common-mode noise components.
Hmmm.. there are very few "fully balanced" microphones today. Most of
them, even the MKH series for example, (and R=F6de NT1A) have pin 3
just AC grounded. So oscillation occurring internally in the mic,
will go straight into pin 2 and never get outbalanced.
The only way I know that mic electronics can make an unclean phantom
power even worse, is when something in the circuit starts to
self-oscillate. But such an oscillation is easy to see on the scope.
And the PRO6 handle is actually only a simple filter and source
follower!? Quite conventional and fully established.
And why shouldn't PRO6 work with a semi-pro machine like the Fostex,
when it works fine with a cheap consumer machine like the Zoom H4??
Klas.
>Regards,
>Raimund
>
>
>--- In Klas Strandberg <>
>wrote:
> >
> > The problem, Rob, is that a those modern phantom power devices may
> > work fine under certain circumstances, with certain microphones and
> > certain loads / temperatures e.t.c. - while they get unstable under
> > other circumstances.
> > There is at least one IC which is 100% stable under all conditions,
> > but then it is a little more expensive than the other ones + you need
> > a coil, which takes space in the machine.
> >
> > Klas.
> >
> >
> > At 19:01 2007-03-21, you wrote:
> > >At 6:07 AM -0700 3/21/07, umashankar wrote:
> > >
> > > >
> > > >i think the culprit in all these is the switched mode phantom power
> > > >and probably the best thing would be an outboarded phantom power. it
> > > >does not always have to be 48 volts - depends on the mike of course,
> > > >but i have run oktava mko12 (a simple resistor for the condensor DC
> > > >voltge) on 18 volts with only a small loss in sensitivity.
> > > >
> > > >umashankar
> > >
> > >This possibility goes way back in our discussions. I bought the parts
> > >to make up one that supplied 48 volts via multiple batteries with
> > >Klas' help on the schematic. A few weeks later, Eric Benjamin tested
> > >my Rolls PB224 portable phantom power supply and reported that the
> > >noise level was probably insignificant even with the best gear. This
> > >was also consistent with my test comparing the NT1-A->744 (phantom)
> > >vs NT1-A-> Rolls PB224 ->744 (non phantom). As the Rolls is only
> > >$70USD, the need for a battery-only unit became lower, but no A/B
> > >test has been done to the best of my knowledge.
> > >
> > >If any one has a battery-only-powered phantom supply they could send
> > >me for a few days, I'll run an A/B test. The NT1-A's will run fine on
> > >30 volts. Rob D.
> > >
> > >
> > >--
> > >Rob Danielson
> > >Peck School of the Arts
> > >University of Wisconsin-Milwaukee
> > >http://www.uwm.edu/~type/audio-art-tech-gallery/
> > >
> > >
> > >
> > >"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
> >
> >
> >
>
>
>
>
>"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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