Hi Raimund,
perhaps, at least to answer some of the frustration & puzzlement about this=
issue, could you let us all know if any other recorders at the pro-sumer o=
r entry level have the same kind of issues & more to the point perhaps, why=
even if they do they appear to be able to handle the DPA's ok ? thats the =
bit I can't get my head round.
--- In "Raimund" <> wrot=
e:
>
> > Hi Raimund, this is indeed a very telling test, but the the imbalance i=
s not as much as you perhaps think. i.e. by leaving the 150R across the pin=
s, from the 48V you have 6K8 to the 2k2 direct and 6K95 to the 2K2 via the =
Message: 150R.
Subject: i.e. a 2.2 percent imbalance.
>
> Agreed, Rob.
>
> > And its supposed to be a pure DC, not contaminated with system noise!
>
> Sure, but it is often a challenge to generate such a perfectly pure DC vo=
ltage out of a low battery voltage.
>
> > Anyway, the point I take issue with is the "poorly designed (unbalanced=
) microphone". The only poor design appears to be the R44 phantom supply, e=
ither a poor return path, poor decoupling or both.
>
> I beg to differ here! The phantom power specification demands perfectly b=
alanced currents on both rails. For that reason, the two internal 6.8 k res=
istors must be matched to within at least 0.4% (see http://en.wikipedia.org=
/wiki/Phantom_power). The microphone itself should therefore also be perfec=
tly balanced. Otherwise, the matched 6.8 k resistors within the recorder wo=
uld be meaningless.
>
> > In principle there is absolutely no reason why one couldn't short eithe=
r of the two signal pins to ground, save that the common mode rejection wou=
ld of course negated.
>
> Hmmm, I'm not sure if that would be a good idea, given that it is quite d=
ifficult to design a perfectly ripple-free phantom power supply.
>
> Raimund
>
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