thanks for all this !
I take it then that its an issue with the recorders rather than the xlr ada=
ptors on the DPA's ? I also assume that given that the telinga has a non-co=
nventional wiring set up thats the reason its having similar issues.
I can only repeat that surely if Roland bothered to test their machines wit=
h these mics, especially the DPA which are so widely used these days, they =
might be able to make recorders that at least compete on this point with an=
ything from a zoom up !
--- In "Raimund" <> wrot=
e:
>
> Hi again,
>
> Because I had some doubts on my quick-and-dirty test setup (there is no s=
hielding around the dummy microphone circuit, which means that it could the=
oretically have picked up "only" electromagnetic interferences from the rec=
order), I just did another test with that unbalanced (and unshielded) micro=
phone dummy, but with the phantom power switched off: http://www.avisoft.co=
m/scratch/R26_0004_1.wav
>
> It finally turned out that it is most likely the noisy phantom power supp=
ly voltage that is causing the noise.
>
> Regards,
> Raimund
>
>
>
>
>
>
>
> --- In "Jez" <tempjez@> wrote:
> >
> > still, for me is the fact that none of this should be needed at all. Ro=
land need to sort this.
> >
> > --- In "sainganrob" <unbalancedmike@>=
wrote:
> > >
> > >
> > >
> > > --- In "Raimund" <raimundspecht@> w=
rote:
> > > >
> > > > Hi Jez,
> > > >
> > > > I just did a quick test with a Roland R-26 in order to investigate =
the quality of its phantom power supply circuit:
> > > >
> > > > I made a simple dummy load consisting of a 150 ohm resistor connect=
ed between the XLR pins 2 and 3. In order to create a load on the phantom p=
ower supply, I also added two 2.2 kohm resistors, one connected between pin=
2 and pin 1 (ground) and the other from pin 3 and pin 1. This creates a cu=
rrent flow of about 10 mA (48V / (6.8 + 2.2 kohm) * 2).
> > > >
> > >
> > > >
> > > > Finally, I removed one of the 2k2 load resistors, which simulates a=
n unbalanced microphone circuit:
> > >
> > > >
> > > > The last recording reveals that the phantom power supply of the rec=
order contains indeed some digital noise that becomes audible, once a poorl=
y designed (unbalanced) microphone is attached to the recorder (a balanced =
circuit would eliminate the phantom power noise).
> > > >
> > > > So, I believe that you could fix the problem with your DPA micropho=
nes by using a better phantom power adapter that draws the same current fro=
m pin 2 and 3.
> > > >
> > > > Regards,
> > > > Raimund
> > > >
> > >
> > > Hi Raimund, this is indeed a very telling test, but the the imbalance=
is not as much as you perhaps think. i.e. by leaving the 150R across the p=
ins, from the 48V you have 6K8 to the 2k2 direct and 6K95 to the 2K2 via th=
e 150R. i.e. a 2.2 percent imbalance.
> > >
> > > And its supposed to be a pure DC, not contaminated with system noise!
> > >
> > > Anyway, the point I take issue with is the "poorly designed (unbalanc=
ed) microphone". The only poor design appears to be the R44 phantom supply,=
either a poor return path, poor decoupling or both.
> > >
> > > In principle there is absolutely no reason why one couldn't short eit=
her of the two signal pins to ground, save that the common mode rejection w=
ould of course negated.
> > >
> > > Rob
> > >
> >
>
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